15.1. INTRODUCTION

This chapter is based on a long-standing quest initiated by one of us (RLB) in 1964 when George Schaller undertook the first detailed scientific study of the tiger (Schaller 1967). It has been rather like chasing a crooked shadow through a maze, for the concept of pheromones in mammals was not well understood at that time and many misconceptions on the social life of the tiger, and particularly regarding the question of olfactory ability of the tiger, obscured the views of latter-day researchers. We have attempted to take into account implications of evolution, ethology, ethochemistry, and ethogenomics while studying the strategies for documenting the different forms of chemical communication in the world of big cats, especially the tiger. Our knowledge in this context was enriched by experiences during several periods of fieldwork in different ecological terrain, in India and Africa, in most of the cases by one of us (RLB). The subject of chemical signaling, only one aspect of which is pheromone, is very wide-ranging. For the sake of clarity and the self-sufficiency of this chapter, we project our views in two ways: in the first part we present a general treatment of chemical signals concentrating mainly on pheromonal signals (communication) in the tiger and other big cats, the lion (Asiatic and African), the Indian leopard, and the African cheetah, and in the second part we will try to substantiate our views with quantitative data records that we have gathered over decades in different phases. Our study on the latter three big cats is less exhaustive than that on the tiger and we have had no opportunity of investigating the jaguar and the cougar (puma).

A major breakthrough in the subject of animal psychology occurred when in 1973, Konrad Lorenz, Niko Tinbergen, and Karl von Frisch won the Nobel Prize for Physiology/Medicine for their pioneering work on animal behavior. A new terminology—ethology—came of age; the terms “ethology” and “animal behavior” became synonymous and now also include sociobiology and related analysis and modeling on behavioral studies from the evolutionary perspective, comparative psychology, and very recently, signal engineering and ethochemistry (as developed in the context of our work on big cats), and so forth.

15.2. HISTORICAL ASPECTS

People living in and around jungles or even in the country (rather than the urban population) had gained inklings of what we today call pheromones and their physiological/behavioral aspects. The strong taint of vixen in reproductive stage (which the dog-fox responds to) well known to people in the British countryside and has been clearly described in a poem by John Maesfield. Likewise, South African farmers were familiar with jackals’ smell in the right season (Van Der Merwe 1953). Such knowledge has been part and parcel of the poacher’s professional skill.

At a more scientific level we can refer to Darwin (1871). In The Descent of Man in Selection in Relation to Sex, he described the strong smell of breeding crocodiles, many mammals, and hinted at a possible sexual selection of such smells. To quote from Darwin, “…if the most odoriferous males are the most successful in winning over females and leaving offspring to inherit the gradually perfected glands and odour…” He described how competition for mates (i.e., sexual selection) would lead to the evolution of traits that either helped a male to fight off other males or to make it particularly attractive to females, or both. He believed that it could be such a powerful force that such a trait could evolve with time. He saw sexual selection as a special case of natural selection with emphasis on mating success. This can be reinterpreted today as the concept of sex-attractant pheromone evolving through sexual selection.

In his book, Darwin also argued that there is an evolutionary continuity and that the root of human behavior patterns lies in many nonhuman animals. The study of pheromones reveals the truth of Darwin’s reasoning. It is now known that pheromones are used by various animals and vestiges of human pheromone have also been traced.

Tinbergen (1951) raised four questions of ethology in his book The Study of Instinct: (1) What is its function and survival value? (2) How has it evolved over time? (3) How has it developed in the individual? (4) What is the physiological causation?

In the following sections we will attempt to address some of the questions raised by him with respect to our findings on big cats.

Animal behavior is not explainable by fossil records. Nonetheless, Rasmussen (1999) indulges in interesting speculations. On the basis of an old report on rock engravings by Pocock (Rasmussen 1999), she suggests that the temporal gland in mammoths was larger in size that that of the Asian elephant. It is possible that in mammoths both males and females utilized this as a source of pheromones. But today it is a major pheromonal source in the male Asian elephant only.^*

We must treat the concepts of instinct, ontogeny of specific behavior related to pheromonal communication, strategies of signaling and their impact on reproduction, phylogenetic relationship of specific behavioral patterns in big cats, in order to understand the facts and hypotheses in the light of evolution. Here we face many problems, some of which are hard nuts to crack.

15.3. PHENOMENON OF CHEMICAL SIGNALING: PHYSIOLOGICAL IMPLICATIONS

The phenomenon of sexual selection is correlated with signaling in most animals. Social signals are diverse; besides visible and auditory signaling, chemical signals (olfactory signals) play an important role in the world of many animals including mammals. These could be urine, feces, glandular secretions, and so forth. Whereas a visual or auditory signal is functional only during the physical presence of the animal, a chemical (olfactory) signal persists even in its absence. Brahmachary (1986) pointed out how such signals might convey information on species specificity, sexual status, and so forth, and Wyatt (2003) lists more information such as on age, health, and fear. Penn (2006) calls such signals an extended phenotype, being inspired by a famous book (Dawkins 1983). Dawkins used this expression to mean “action at a distance” as in the case of the Bruce effect; here the pheromone helps the second male (physically absent) to block pregnancy of the female due to the sperm of the first male, thus acting to the advantage of the second. We feel, however, that in a more general sense pheromones are also extended phenotypes leaving their “individuality imprint” at a distance, such as in the scat, dung, urine, and glandular secretion. We will return to this theme in the context of big cats.

Maynard and Harper (1988) divided signals into two categories, assessment and conventional. They explained that assessment signals are “honest” in function and involve a large expenditure of energy (e.g., the loud call of a barking deer). Conventional signals are generally prominent display badges such as the tusks of the male Asian elephant, large shaggy mane of the African lion, brightly colored feathers/wings of birds like that of widow bird or peacock; these are signals or certificates attesting good health, virility, high nutritional status, and so forth in the organisms (Brahmachary 2011). Sometimes these signals are misleading (e.g., the black bib of the house sparrow is not always correlated with male dominance) (Maynard and Harper 1988). As we will see, in the big cats the major pheromonal signal is based on metabolic expenditure, namely the loss of a large amount of lipids, presence of hormones, or derivatives thereof in urine and marking fluid (MF) (see Section 15.6.1). This ability of metabolizing energy as well as the traces of hormones in urine, MF, and so forth can claim to be honest signals, as we will describe later.

The difference between hormone and pheromone is generally clear. Hormone, which means “I excite,” is restricted to an individual body, while pheromone, which connotes a sense of “carrying” (pherein) excitement, is concerned with transmission of “excitement” (here, a chemical signal) to another individual. However, a comparative study on heterosexual and homosexual men and heterosexual and lesbian women by Berglund et al. (2006) suggests that certain sex hormones and their breakdown products also act as pheromones. He reported that two compounds, progesterone derivative 4,16-androstadien-3-one (AND) and estrogen-like steroid estra-1,3,5(10),16-tetraen-3-ol (EST) induce sex-specific effects on the autonomic nervous system, mood, and context-dependent sexual arousal. Thus AND and EST are supposed to be candidate compounds for human pheromones. Therefore, we feel it is unnecessary to take recourse to hair-splitting while defining terminologies.

15.4. SEMIOCHEMICALS AS STIMULI

“Semeion” means signal (as in semaphore signal) in Greek. So, semiochemicals include all signals in our biological context; it may be the mRNA, a signal from DNA, an osmic (smelly) chemical signal emitted by an animal that excites another animal of the same species (pheromone) or alerts the prey, or the smell of the prey can betray it to the advantage of the predator. The last two cases have been described as allelochemicals by Nordlund and Lewis (1976) and are subdivided into two other classes—kairomones and allomones. However, these two terms were well defined by Claesson and Silverstein (1977) and in Chemical Signals in Vertebrates I (1977, Plenum Press, London) and we feel the term allelochemical might lead to confusion for this is well known in modern Botanical literature as the classes of substances emitted through root exudates or material leaching out of leaves shed on ground and affecting the growth of plants of the same or other species. We, therefore, are of the opinion that the terms pheromone, allomone, and kairomone are sufficient to describe the relevant issues.

The concept of the pheromone has further been categorized into “releaser” and “primer” depending on the time gap between exposure to the pheromone and the response in the receiver, either immediately or after a longer duration (Albone 1984). The interim period between stimulus and the response may vary; action can be instantaneous or delayed depending on orientation of stimuli, gradual accumulation of information, or controlled response with the influence of environment. Stimulus of smelling the young triggers the final letdown of milk from a lactating mother, although prior growth of the mammary gland is accelerated by the cumulative arousal action of the pregnant female by grooming or licking the nipples in rodents (Manning and Dawkins 1992). Ewert and Trand (1979) correlated the selective responsiveness to key stimuli at a behavioral level with the underlying neurobehavioral mechanism. In other words, the strength of responsiveness or motivation to the stimuli depends on various internal and external factors of the receiving animal.

“Communication” has generally but not always evolved for the sake of mutual benefit of sender and receiver (Manning and Dawkins 1992). In our view, when interindividual communication takes place within the same sex to reduce direct confrontation with rivals, it is beneficial to the sender but not to the receiver. On the other hand, communication between the opposite sex is beneficial for both individuals. Communication (i.e., the passage of ‘information) may also be disadvantageous in the context of the predator-prey relation. However, the latter aspect will not be treated because our focus is on intraspecific communication through pheromones. Chemical communication as a sex attractant or warning signal in the context of territorial connotations necessarily includes a self–nonself distinction (i.e., those signal(s) as those that bear the characteristic individual signature). Wyatt (2003) emphasizes this aspect as well as that of kin or clan recognition as distinct from pheromones, but it would be less complicated to retain the term pheromone and interpret it in a wider context.

15.5. HOME RANGE AND TERRITORIES

The aspects of home range and territories include a study of sex allocation and amenities such as availability of food, water, and abode, and are related to social conduct. Territory may be permanent or temporary and a territory holder is perhaps dominant over an intruder. Most territories and home ranges can be more clearly understood in the description by earlier authors as mentioned below. More data has been furnished later.

Many hunters in the past talked of tiger beats rather like the beat areas of police officers. When a tiger was killed, very soon its particular niche was filled up by another. “A good tiger beat is sure to continue to be so year after year” even when the “predecessor may have been killed but recently” (Fayrer 1875). Likewise, Lyddeker (1893–94) mentions observations docketing the fact that when “a tiger with a restricted beat is killed…another will occupy its place frequenting the same lairs and drinking at the same pools.” This view, based on a good deal of experience and also verbally communicated (to RLB) by Wakefield, an old-time hunter naturalist of vast experience of Indian wildlife, implies territoriality or home range but in the scientific world the concept was formulated by Howard (1922) while describing British songbirds (their song is a vocal communication). Uxkuell (1934) used two words, Heim and Heimat, both of which in German have the connotation of home. Taking this cue, ecologists and ethologists later on introduced two terms, territory and home range. A territory may be defined as that part of home range which is actively defended (Burt 1943), if need be, by fighting. In the 1940s and 1950s Hediger clearly propounded the idea that animals reserve separate sections of their home range for specific, different purposes, such as sleeping, resting, defecating, and wallowing (Hediger 1977). Only some part(s) of the home range are actively defended but signals with agonistic connotation such as roaring or the olfactory cues based on fresh pheromones minimize the chances of an all-out fight. However, in other parts of the home range the presence of others is tolerated or even encouraged. Some authors have used the expression “land tenure” rather than territory/home range in the context of big cats.

Barnett (1981) mentioned four kinds of factors for confinement of an animal in its territory: (1) existence of structural barriers for movement, (2) the attraction of the place due to various reasons, (3) due to specific apotreptic behavior that keeps animals apart, and (4) the animal may withdraw itself on detecting the presence of conspecifics. We feel the first factor (structural barrier) is an exceptional case. Also, the difference between (3) and (4) is not clear-cut. According to Powell (2000) home range represents an interplay between the environment and an animal’s understanding of that environment (i.e., its cognitive map). Home-range behavior is the product of a decision-making process shaped by natural selection to increase the contributions of spatially distributed resources to fitness (Börger et al. 2008; Mitchell and Powell 2004; Spencer et al. 1990). For demarcation of territory, animals use optical, acoustic, olfactory, and chemical cues or a combination of these so that other conspecific members can recognize it in several ways. Anderson (1994) classified territories under different categories: (a) a region in which most or all activities of the animals are carried out, (b) a region smaller than the total area of movement of the animal (i.e., territory is a subset within a big set of home range), and (c) a region in which a female raises her offspring.

In a natural or stable environment, territorial behavior, though diverse, entails an orderly and often peaceful spacing out of the population so that most individuals can carry out essential functions like searching for food, prospective mates, raising young, and so forth without much overt aggression. Thus in the tiger and lion territorial behavior is linked with breeding and raising offspring (Locke 1954; Schaller 1967; Schaller 1972).

15.6. SCENT MARKING IN BIG CATS

15.6.1. Unknown Spray

In about a century and a half of numerous blood sport literature, the behavior pattern of the tiger, originally called the unknown spray and now known as scent marking, was conspicuous by its absence. Even stalwart oldtimers like Corbett (1944), James Inglis (1892), and Dunbar Brander (1923) apparently never noticed this now so familiar phenomenon (today it is well known that tigers, lions, leopards, etc., frequently eject a fluid through the urinary channel like a spray directed upward). Schaller (1967) unearthed a single reference, that of Locke (1954). This discerning military officer wrote tersely but to the point, “From time to time, presumably when in quest of a mate or when wishing to indicate that he regards this area as his own particular hunting ground, the adult male is capable of ejecting a strong smelling secretion from beneath the tail, which is raised vertically during this process. The fluid is expelled upwards and backwards with surprising force. The spot which the tiger has chosen for this purpose can easily be recognized by the odour. Traces of the fluid may also sometimes be found on surrounding vegetation including the undersides of the leaves on low hanging boughs.” His views essentially are valid even today. But he saw only the male tiger spraying. In 1964, Schaller in Kanha, India, noticed a tigress raising her tail and spraying a fluid through the urinary channel upward and backward and later he observed this behavior a few more times. Schaller was toying with a theory that this spray might encode certain information to be decoded by other tigers (Schaller 1964, personal communication). One day in 1964, Schaller and one of us (RLB) noticed a long file of spotted deer pausing and smelling the leaves of a stunted Butea monosperma tree that was apparently sprayed by the resident tigress (Brahmachary 1964, personal field diary). In 1967, Schaller first brought this spray to the notice of scientists through his book (Schaller 1967). At a later date, while watching a tame tigress in a jungle in Orissa, India, 52 sprays were noticed in a single day (Brahmachary 1976, unpublished personal field diary) and hundreds of sprayings were subsequently observed in a very large compound where the tigress had a free run. Much of this data was documented by S.R. Choudhury, who had been studying this tiger from cubhood (Figure 15.1) since 1974. (Some of this data was published posthumously [Choudhury 1999].) Around the 1980s many naturalists and even casual tourists in Indian National Parks became familiar with the spray of tigers.

FIGURE 15.1

”Khairi” (born August 1972; died September 1977): the pet tigress of Simlipal forest, which initiated scientific research in tiger pheromones. (Photo courtesy of Mr. Dilip Bhattacherya.)

The tiger indeed employs this fluid for attracting mates and staking a claim on its hunting territory. Actually, unlike the tomcat, the female (known as the queen), sprays very infrequently. The same is valid for lionesses (Brahmachary and Singh 2000; McBride 1977; Schaller 1972), leopards (Poddar-Sarkar and Brahmachary 2004), and cheetahs (Caro 1994; Eaton 1974; Poddar-Sarkar and Brahmachary 1997). In these species the female rarely marks, generally only during the onset of the estrous stage, but the tigress marks very frequently, almost rivaling the male as we will see later. Of the other members of the cat family the female serval sprays frequently (personal communication from staff at Moholoholo, South Africa, in 2005).

Comparative ethology of spraying MF has been studied in the tiger and lion. In the African lion Schaller (1972) noticed that the direction of the spray varies rather widely, upward and backward, horizontally backward, and simply downward (without assuming the squatting posture adopted during urination). In the Asiatic lion Brahmachary et al. (1999) also detected such modalities. In the tiger the direction is more fixed—almost always upward and backward (Brahmachary et al. 1999; Poddar-Sarkar et al. 2013). Barja and Miguel (2010) observed Siberian tigers (P.t. altaica) and Barbary lions (P. leo leo) in a Madrid zoo. They reported what they consider to be significant differences in the marking behavior of the tiger and lion, namely that the frequency of marking occurs more in the tiger while the marking duration act occurs more in the lion. They have attempted to correlate these (and other) differences with the social/asocial nature of the two species as well as with their habitat differences (forest versus open area). The tiger shows seasonal variation in marking patterns whereas the lion does not. They also correlated many environmental factors in addition to their reproductive physiology (seasonal polyestrous versus annual polyestrous). Such extrapolations from a European zoo to the natural conditions of Siberia and Barbary of Africa are difficult. Moreover, the now-extinct Barbary lion was an unusual race of the African lion.

15.7. MAJOR HISTOCOMPATIBILITY COMPLEX OF GENES AND INDIVIDUALITY IN PHEROMONAL SIGNALS OF BIG CATS

A very relevant question is whether and how the mark of individuality is imprinted in the chemicals purported to be pheromones, for essentially all territorial connotations of pheromones are based on the distinction between self and nonself. Brennan (2008) reported that, “…recognition of individual identity and relatedness of individuals play vital roles in mammalian social behaviour (for most vertebrates). Individual and kin recognition depend on being able to detect and discriminate differences in genetically determined chemosensory signals. In identifying these chemosensory signals of individual identity…the best known are the genes of MHC.” Compounds produced through the expression of polymorphic major histocompatibility complex (MHC) genes are thought to influence individual odor and pheromone production, thereby facilitating an olfactory cue for kin recognition and mate choice (Chong 2009). Jeffery and Bangham (2000) and Kelley et al. (2005) proposed that MHC diversity is maintained through two forms of a balancing equation: heterozygote advantage and natural-selection-dependent frequency over long periods of evolutionary time. These facts imply distinguishing self from nonself (Brahmachary et al. 1993; Brennan 2008; Hurst et al. 2001; Yamazaki et al. 2000). Although “self/nonself ” recognition is controlled by diversified MHC class I and class II MHC genes (the most polymorphic loci known in vertebrates), many species show limited or no MHC diversity; for example, experiments for skin grafting between individuals of unrelated cheetahs (Acinonyx jubatus) are successful, indicating that these African cats have little MHC diversity (O’Brien et al. 1986). Similarly, Asiatic lions (Panthera leo persica) show very low MHC diversity, indicating genetic bottleneck (Penn 2002).

However, genetically identical inbred mice have a significant variability in the proportion of volatile urinary components, suggesting that nongenetic factors, such as nutrition and environmental condition, also have significant effects on individual urine odor (Rock et al. 2007). MHC-related genome study of big-cat lineage (in which species divergence began 5–8 million years ago) revealed that there is 93% nucleotoide sequence similarity between class I transcripts in the cheetah, 93%–99% similarity in the ocelot, and 92%–100% similarity in the domestic cat when compared between species and only a 13% variation exists in all felidae for species-specificity (O’Brien and Yuhki 1999). According to Brennan (2010), no specific explanation is now valid for establishing the mechanism by which MHC genotype could affect metabolic pathways to account for the reported quantitative differences in urinary volatiles of individuals. Urine samples from MHC-congenic mice have consistently different proportions of volatile carboxylic acids (Singer et al. 1997).

The use of police dogs in hounding out criminals on the basis of their distinctive body odor is well known. We may here consider the old data on establishing 41 different parameters as star-shaped lines representing such ensembles of compound on human beings that apparently are characteristic for each individual (Strauss 1960). The police dog might be working on some such basis. Distinguishing an individual mongoose among 24 on the basis of ratios of 12 carboxylic acids characteristic for every individual mongoose was reported (Gorman 1976; Gorman et al. 1974). In a preliminary attempt we tried to investigate this aspect in the tiger (Poddar-Sarkar and Brahmachary 1999). It revealed a more complex situation in the tiger. Seasonal variations in the proportions of 10 carboxylic acids were noted but the patterns of a mother and son were much closer than that of a distantly related tigress. More recently, a more detailed study of such proportions has been carried out on Lemur catta (Palagi and Dapporto 2006). In view of recent findings on dogs smelling out and distinguishing different scats, trained dogs might be used for matching the smell of individual tigers by sampling fresh scratch marks, MF, and scats in a tiger census (Wasser 2009).

15.8. GENOMICS, PROTEOMICS, AND METABOLOMICS IN PHEROMONE RESEARCH OF BIG CATS: THE SEARCH FOR THE EVOLUTIONARY LINEAGE AND LINKAGE OF BIG-CAT POPULATION

A number of attempts have been made to quantitate the relatedness of different big cats with the help of recent molecular techniques but unequivocal results have not been obtained. For example, Davis et al. (2010) pointed out that “despite multiple publications on the subject no two molecular studies have reconstructed Panthera with the same topology.” To trace evolutionary history among the eight subspecies of tiger (Panthera tigris), three of which are extinct, a number of genetic markers like 4-kb mtDNA sequence, allele variation in the nuclear MHC class II DRB gene, and composite nuclear microsatellite genotypes based on 30 loci have recently been carried out (Davis et al. 2010). Amplification, cloning, and sequencing of alpha-1 and alpha-2 domain of MHC class I and beta-1 domain of MHC class II DRB genes from scat of 16 wild and captive Bengal tigers (Panthera tigris tigris) of different geographic origins of India reveal a low number of MHC DRB alleles but high variability in peptide-binding sites (Pokorny 2011).

In 13 different attempts, the tiger, lion, snow leopard, clouded leopard, jaguar, cheetah, and cougar (puma) have been considered and the results are far from unequivocal (only one attempt included the cheetah and cougar). However, Davis et al. (2010) considered all old data as well as new sequences “generated for 3 single copy regions of the Felid Y chromosome as well as 4 mitochondrial and 4 autosomal gene segments” and Bayesian statistics to establish phylogenetic trees (Bayesian estimation of species trees). On the basis of this attempt they claim “monophyletic origin of lion and leopard, with jaguar sister to these species as well as a sister species relationship of tiger and snow leopard.” Likewise, the subspecies/races of the tiger have also been studied from the genomic perspective, and with certain reservations, it has been accepted that the Amur (Siberian) race and the now-extinct Caspian race (samples of which were obtained from a museum specimen) are phylogenetically close as determined with the help of mitochondrial DNA sequences (Driscoll et al. 2009). The Bengal tiger (P. tigris tigris), the Sumatran tiger (P.t. sumatrae), and the Chinese tiger (P.t. amoyensis) are distant branches. Cracraft et al. (1998) had earlier suggested that the Sumatran tiger is distinct from the Asian mainland races. There is an indirect implication of this race genomics on pheromones.

From the biochemical perspective of metabolic products acting as pheromones, cauxin, a 70-kD MUP protein that belongs to the carboxylesterase (CES) superfamily attracts our attention. Cauxin answers for about 90% of total MUP in the smaller felids like the domestic cat. but it has not been detected in nonfelids. It is fivefold less in the Pantherine line (e.g., lion, jaguar, tiger, and leopard) (Li et al. 2011; McLean 2007; Miyazaki et al. 2006). Datta and Harris (1951) and Westall (1953) reported felinine, a characteristic molecule in urine of both the sexes of domestic cat which, as it now turns out, is a hydrolyzed product of cauxin. Interestingly, felinine has not been detected in Panthera (Hendrik et al. 1995). The exact role of cauxin is uncertain; we do not know whether it plays a role as a nonvolatile pheromone such as aphrodisin or a pheromone-binding protein. Nonetheless, genomics of and possible selection pressures, both positive and negative, on this protein are interesting from the perspective of evolution of the cat CES protein family. This might be worth pursuing in the future. These facts remind us of the Darwinian concept of natural selection between and within cat families. However, as already mentioned, the exact role of cauxin is uncertain.

Metabolomics in the context of 2 acetyl-1-pyrroline (2AP), an interesting component of MF and urine of both sexes of the tiger and leopard but not of the lion and cheetah, has been treated in Section 15.10.2.1.1. The two main large cat clades, one with lion-leopard-jaguar and the second with tiger-snow leopard as proposed by Hemmer (1974), Johnson et al. (1996), Bininda-Emonds et al. (2001), and Nowak (2010) on the basis of mitochondrial RFLP analysis and on excretory chemical signals may open up a new vista for establishing evolutionary lineage of felids. Bininda-Edmond’s approach by studying the lipid chemistry of anal gland secretion of 32 lions and 22 tigers (though the pedigree or purebreed was not mentioned and the sample sizes from other felids were relatively small) established the nearest relationship between the lion and leopard. Thus, in the future, after analyzing more metabolites one might find a different metabolic picture.

Therefore, the evolutionary history of the emergence of the cat lineage still remains incomplete and we are yet to write it in a more rational and logical way. Many authors proposed that the pantherine line has a comparatively recent origin of about 3.8–4.6 million years but the individual speciation event occurred only 1 million years ago by gradual amalgamation of introgressive characters and favorable divergence.

15.9. QUANTITATIVE APPROACH FOR UNDERSTANDING THE TERRITORY AND HOME-RANGE IN THE TIGER COMMUNITY

15.9.1. Territoriality in the Tiger

Baker wrote that the tiger is not the unsociable creature it is commonly understood to be; on the contrary it is fond of consorting with others (Baker 1887). Forsyth reported seven adult tigers in a patch of cover (Forsyth 1872). Schaller also saw seven adult tigers around a kill (Schaller 1967). McDougal (1977) refers to a larger association, nine tigers, but an impressive example that has apparently escaped the notice of wildlifers and tiger specialists was reported by Eden, namely as many as 15 tigers in a patch of cover (Eden 1837–38). In more recent times an association of nine tigers (including both males and females) amicably feeding has been reported in Ranthambhore, India (Thapar 1986). McDougal (1977) noted while offering a ready-made supply of food (bait) that more than one tiger would feed from this source, though generally not simultaneously. Schaller (1967) and McDougal (1977) described the home range/territorial system of tigers; a tiger/tigress has a center (or more than one center) of activities within its range where it spends most of the time. The extensive data on tiger territory gained by the Smithsonian group in Nepal revealed that males establish territories ranging from 19 to 151 sq km while female territories range from 10 to 50 sq km. In seven adjacent areas of seven tigresses in Nepal, the Smithsonian scientists noticed overlaps between the areas of tigers 2 and 3, tigers 5 and 7 and tigers 6 and 7. They studied the details of gradual separation of mother and daughter into different territories after 2 years of total overlap.

Ranges/territories may extend from a few square miles (Schaller 1967) to 1200 sq km for the Siberian tiger (Thapar 2006). Home range/territory is determined by the number of animals, assurance of food such as prey density, and for the tigress, certain amenities (including food) and for properly raising cubs. As the tiger generally stakes out his claims over an area in which more than one tigress have their smaller areas, the tiger automatically ensures an area with prey. This trend would basically be applicable to the other big cats. In India, Panwar (1987) recorded that a male territory may enclose more than one female territory. In Chitawan, Nepal, a male tiger’s territory enclosed those of seven tigresses. We have seen that tiger territories/home ranges vary widely. Very recently much detailed data has been gathered in the relatively small Indian National Parks. One example is that of a radio-collared tiger translocated into Sariska National Park which for about 1 year held an average home range of 140 sq km, including a largely overlapping smaller range of a female (Bhattacharjee et al. 2012; Sankar et al. 2012).

More pertinent to our theme is the role of pheromones in territorial and mating strategies. As McDougal (1977) stated, “Defence—rarely means fighting tooth and claw with intruders. The occupant advertises its presence through various means of marking its environment.” Theoretically, the tiger, or for that matter, a lion or any other big cat, can ill afford to indulge in an all-out fight because even the winner will sustain injuries resulting in a handicap so far as catching prey is concerned. This may thus spell the doom for the winner, too, though in case of the group or pride of lions it will be less disastrous. Overt proclamations such as roaring or pheromonal messages are warnings likely to minimize the chances of such fighting.

It might be relevant to mention here that in Panna and Ranthambhore, India, about 25% and 35%, respectively, of male tigers are killed by fighting among themselves (Chandawat 2002, 2006; Thapar 2006). In view of the vast potential for inflicting injuries the toll of tigers could have been much higher unless a certain mechanism of restraint had been operant. The same must be valid for other big cats but in the lion one has to consider collective defense of the territory and pride and that collective attempt of a “bachelor gang” win over a pride/territory (McBride 1977; Packer et al. 1991; Packer and Pusey 1997; Schaller 1972). In a more popular vein, Jackman recorded such details (Jackman et al. 1982).

Carrington-Turner stated that tigers in their postprime period of life tend to be displaced toward the periphery; they have to abdicate and opt for suboptimal areas (Carrington-Turner 1959). More precise and modern reports are those by McDougal (1977), Smith et al. (1987) (Nepal), and Panwar (1987) and Thapar (2006) (India). It seems tigers in pre- and postprime conditions are unable to establish territories in the most favorable areas; they are forced to occupy peripheral zones. Thapar (2006) reported that in Ranthambhore, India, the young male tigers are forced to move to the peripheral areas; later they return and try to occupy territories in optimal areas. An example of forming a boundary by marking six trees with a diameter of 90 m by a female while litter-dropping and raising cubs was reported by Singh (Singh 1981).

To understand the territorial behavior of the coinhabitant and neighboring tigers by marking MF under a common open-air condition of a tropical climate we formulated several models within many constraints, problems of logistics, and limitations beyond our control.

We have selected an open-air enclosure for showcasing a nearly natural wildlife situation under captivity where animals have developed zoo-specific cognitive behavior in addition to their instinctive behavior. We have recorded data on MF spray, urination, scat deposition, and flehmen over about 5 years (with some gaps) at Nandankanan Zoological Garden (20°23′45.59″ N, 85°49′21.59″ E), Orissa, India. Detailed answers to the following questions will be attempted:

• 1. Whether marking is preferential or random
• 2. Whether there is any differential approach for marking by females and males due to the presence or absence of same or opposite sex in the neighborhood
• 3. Whether the territorial demarcation of one individual overlaps with another when they inhabit the same territorial zone
• 4. Whether the total area covered is a determining factor for frequency of marking
• 5. What the relative difference between the frequency of ordinary urination and MF spray and the respective difference between male and female is
• 6. Whether frequency of MF spraying has any correlation with the reproductive status of the female and male
• 7. Whether there is any correlation between MF spray and flehmen
• 8. Whether the incidence of MF spray, flehmen, etc. occurs at an early age in big cats

To test the concept of putting differential emphasis (actively defended territory and less actively defended territory) over different parts of home range, two experimental approaches have been framed:

• 1. Spatial distribution of marking at different locations of the enclosures by considering (a) the frequency of marking on each specific location and (b) MF spray per unit length of the boundary
• 2. By considering location-wise tree-marking to conceptualize a miniature home range under this captive condition and thus to extrapolate the basic strategy of MF spray for maintaining the territory and home range in the Bengal tiger

15.9.1.1. Study Design and Strategy

Data on the MF spraying of 12 tigers confined in four different groups (Gr I, II, III, and IV) in four enclosures (En. 1, 2, 3, and 4) were considered for the study (Figure 15.2; Tables 15.1 and 15.2). Each enclosure has a brick-built structure for dropping food and as a shelter (S) with two-way doors through which tigers can go in and out, a water-filled moat for swimming, a grassy sward, and many trees. A continuous high iron chain-link mesh (demarcated as “C” in Figure 15.2) divided En. 1 and En. 2 and similarly En. 3 and En. 3A. Each of this mesh runs from one corner of the enclosure, passes through the water moat, and ends on the other side of the enclosure (the “B” side of Figure 15.2) from where observation was recorded. Observation was carried out on Gr I comprising male M1 (stud book^* No. W363), and females F1 (No. 356), F2 (No. 358), and F3 (No. 357) for 13 months (duration of study: June 1987–June 1988); Gr II comprising F4 (No. W360), F5 (No. W362), and F6 (No. W359) was observed for 7 months (study duration: December 1987–June 1988) following the previous schedule; Gr III comprising M2 (No. W325), F7 (No. W296), and F8 (No. W331) for 4 months (duration of study: August 1988–November 1988); and Gr IV comprising M3^* and F9^† for 5 months (duration of study: October and November 1988–February 1989) on a 3-hour daily basis from 8:30–11:30 AM after ascertaining the period of brisk activity. The members of Gr I and Gr II resided side by side in these two adjacent enclosures (En. 1 and En. 2) and could communicate with each other only through visible and audible cues. Similarly, Gr III resided in En. 3 who had as neighbors one male and one female in En. 3A. Each enclosure had an annexure part (Annex En. 1, Annex En. 3, etc.; “D” in Figure 15.2) separated from the main enclosure with the same type of chain-link mesh boundary. Members of main enclosure and the Annex enclosure could also communicate by visual and tactile cues through the chain-link mesh. During collection of MF for chemical analysis the animals usually had been driven to that annex part (Figure 15.2). There was a huge vacant piece of land beyond a similar type of iron chain-link boundary (the A side of Figure 15.2) of En 1 and therefore shared with no other members. There was a 60-ft gap between En 2 and En 3. The approximate area covered by En. 1, En. 2, and En. 3 was about 10⁴ square feet. The situation of En. 4 was quite different and smaller, about 1200 square feet with a tiny triangular water body inside, surrounded by a similar type of iron chain-link mesh traversing in between En. 4 and En. 4A and having an annex part in one side as in Annex En. 4 (“D” in Figure 15.2). There was a lone male on that side. En. 4A was occupied by a male and a female.

FIGURE 15.2

Site plan of enclosures (not to scale) for observation at Nandankanan (20°23′45.59″ N, 5°49′21.59″ E) Zoological Garden, Orissa, India. (A detailed design is available at www.panoramio.com/photo/23742383.) (more...)

TABLE 15.1

Spatial Distribution of MF Spraying by Different Members of Gr I, II and III

TABLE 15.2

Spatial Distribution of MF Spraying by Members of Gr IV

15.9.1.2. Overview on Marking Patterns

15.9.1.2.1. Test Hypothesis I

To address questions 1, 2, 3, and 4 above, we considered five locations (shelter (S), common boundary (C), no-member boundary (A), boundary in Annex part (D), and trees [T]) for recording data. Observation from the B side of specific enclosures (Figure 15.2) was considered only when certain tigers roamed at ease and least disturbed by visitors. It is to be noted that tigers in different assortments were arranged by zoo authorities and could not be altered at our will, so the tigers had to be studied in accordance with the regime of this public zoo.

Under these circumstances (vide Case studies 1–4), certain relevant data in relation to questions 1–4 have been furnished in Tables 15.1 and 15.2.

The answers to the above questions are as follows:

• 1. The frequency of MF spray is differential (i.e., higher in males than in female) (see also Figure 15.3).
• 2. The very first conclusion that emerges is that tigers prefer to mark maximally at the shelter where they get food and retire during inclement weather in all cases.
• 3. The length of the boundary is not the prime factor for marking by the tigers; however, the presence of neighbors (and their sex) beyond the common boundary (which can be conceptualized as possible “intruders”) is the most important factor for frequency of marking. The boundary beyond which there is no neighbor was less important for the resident members.
• 4. Under restricted captive condition the combination of sexes of coinhabitant members and neighboring members exert a direct influence on frequency of marking. When the combination of sexes in a neighborhood has been altered the spatial distribution pattern of MF spray changes. The above behavioral pattern may project an insight in the breeding strategy of zoo tigers.
• 5. From Tables 15.1 and 15.2 it is also revealed that under the limitations of captive situation, within a common home range tigers maintain specific location-wise nonoverlapping territories. When they are in combination they mutually select the location of preference for spraying MF depending on the combination of resident and nonresident members. It is also explained through a contour map drawn on the basis of frequency of marking on trees (Figure 15.4a to d).
• 6. The synchronization in frequency of marking among the coinhabitant members during proestrous, estrous, and postestrous have been observed (Figure 15.5a,b). It was also observed that the rate of marking by a tigress increases during proestrous and suddenly falls during estrous and again rises to normal at postestrous. The coinhabiting male also behaves in a similar way.
• 7. Synchronization in MF spray and flehmen incidence was also observed in some cases (Figure 15.6). Therefore, all the observations support the hypothesis that MF does act as a means of communication among tigers.

FIGURE 15.3

Tree-marking by different members of Groups I, II, III and IV.

FIGURE 15.4

a–d: Contour map drawn on the basis of frequency of MF spray on 23 trees by Gr I members (a = F1, b = F2, c = F3 and d = M1) of En. 1 during June 1987–June 1988. (•) = location of trees, tree no. (•14), tree no. (•2); (more...)

FIGURE 15.5

(a) Differential marking pattern of M1 and F1 during different reproductive phases. X-axis indicates specific date from 04/19/88 to 04/29/88. Mating event occurred during April 22 to 25, 1988. (b) Differential marking pattern of M1 and F2 during different (more...)

FIGURE 15.6

Correlation of MF spray and Flehmen incidence of Gr I members during every month of observation. Observation was taken maintaining the schedule mentioned in Section 15.9.1.1.

Case Study 1: En. I with Gr 1

The introduction of a member beyond one boundary changed the spatial distributional patterns of marking by the resident members and thereby strengthened the above view. For a short while F1 was transferred for a few months to Annex En. I. M1 of Gr 1 could interact with her through the chain-link mesh (i.e., the boundary between En. I and Annex En. I; vide “D” in Figure 15.2). Now 448 out of 1442 total markings of M1 was noted to be on that side, which was never marked before (duration of observation: 137 hours 20 minutes).

Among the three tigresses of En. I who were litter mates and so of the same age, F3 marked significantly less (Table 15.1), which might be correlated with a low dominance rank.

Case Study 2: En. II with Gr 2 and En. III with Gr 3

Another experimental model revealed a differential pattern of MF spray among the resident members of a single group. This depended on the presence and particular sex combinations of a neighboring group in an enclosure 60 feet apart (vide Figure 15.2 and Table 15.1 for the combination of resident and neighboring members in these two enclosures; members could communicate by vocalization but not by visible cues). The preference for MF spray depended on the strategy of “defense against the same sex.”

Case Study 3: En. IV with Gr 4

The composition of this enclosure was quite different and the members were very attentive to spray at both the common boundaries (“C” and “D” of En. 4 of Figure 15.2; Table 15.2) because there were neighbors on both sides.

Case Study 4: En. I with Gr 1 and En. IV with Gr V

In order to test the hypothesis that the enclosure area (represented here as length X breadth of boundary) has no bearing on the frequency of marking, we considered En. 1 (~10,000 sq ft) and En. 4 (~1200 sq ft). Data on frequency of MF spray per unit length on the common boundary and on the boundary without neighbors revealed an interesting feature, namely, marking frequency does not depend on the length (vide Tables 5.1 and 5.2). The equivalent statement is that MF frequency is not higher on longer boundaries or less on shorter boundaries. So, once again we see that the assortment of neighbors/combination of sex, rather than the area, is the factor that determines the frequency of MF spraying.

15.9.1.2.2. Test Hypothesis II

After getting a preferential overview on marking pattern we have undertaken the second experimental approach to map the location-wise distributional trend of marking on trees by each individual of Gr I tigers throughout the year in different seasons. It was possible to consider the MF spray on trees only within En. I (between June 1987–June 1988) containing 23 trees of different families, shape, height, and width of the tree trunk and canopy. Three females of Gr II resided in adjacent En. 2 as mentioned previously. The spatial distribution of markings over 23 trees by three tigresses (F1, F2, F3) and one tiger (M1) and the density of spraying of MF on each tree were calculated. Two-dimensional contour maps for each tiger was developed by moving average isopleths (Davis 1973) using SYSTAT 7.0 (Figure 15.4a to d) by placing 23 trees on an x and y locational grid and z as marking per tree. The area of the enclosure comprising the trees was divided into square grids of equal size in such a manner that each grid would contain at least one tree. All the data within this grid were averaged and the mean value assigned to the central point of the grid and subsequently the mapped area was contoured at suitable contour intervals (here, 5-15-25-35— — — — n) for each member (Figure 15.4a to d).

Of these 23 trees most markings were on tree numbers 1, 2, 4, and 14. The data indicated that tree T 2, which had a thin trunk and small canopy, received the highest degree of markings (446 by all the members) possibly because of its location, namely proximity to the common chain-link mesh as well as shelter. T 14 (vide Figure 15.3) received the second highest number of markings (344 by four members) although it had the thickest trunk and widest canopy. No preference for a particular tree species was evident from our observation. That both the trees were frequently marked is an indicator that the width of the trunk is not an innate releasing mechanism (IRM), it does not elicit more spraying. (This is also relevant to the wall of the shelter, which resembles a very wide tree trunk.) Although Smith et al. (1989) suggested that the rate of marking on trees may depend on the diameter of tree trunk and angle of lean, our results indicated that the location of the trees rather than their width and canopy spread is important with respect to spraying and that within this common area each tiger had staked out a preferential zone.

The contour lines further suggest that markings are preferential rather than random because all the members of this group preferred to mark on trees located near the common iron chain-link mesh where there were three female tigers beyond the C side of the Y-axis (Figure 15.4a to d). Tigers were not very attentive to sprays on the trees beyond the opposite side (i.e., the A side of the Y-axis) which was lying vacant. Therefore, trees located near that side received less density of marking.

It is evident from Figure 15.4 that every tiger had a nearly nonoverlapping contour and the contour lines with highest value were closer to the shelter and common boundary. The highest contour value of the male along the C side of the Y-axis covering a wider zone (almost the entire length of the common boundary) also signified that he not only advertised himself to the females of his own enclosure but also to the neighboring females of the adjacent enclosure. Theoretically, there are two possibilities:

• 1. Straight lines running through the locations of maximum value along contour lines of different tigers lie at different points along the common boundary in every case. That would indicate the view of a group behavior. In the case of group behavior, we would expect that every tiger would prefer to mark at the common boundary (C, i.e., the Y-axis).
• 2. Contour maps having unique features signify uniqueness for individuality. Figure 15.4a to d indeed suggests both these phenomena.

In a common miniature home range, territoriality is always maintained for every individual member of a group. In nature tigers holding individual territories as well as tolerating certain overlaps are well known (McDougal 1977; Singh 1981; Thapar 1986). They describe amicable feeding in free-ranging tigers and Smith et al. (1987) show overlapping and shifting of home range/territory. It is worth noting that even within the outdoor enclosure shared by four captive tigers, there is a tendency of tree marking that reflects a sort of partitioning of this restricted home range for each individual as evident from the contour analysis data.

All these facts strengthen the hypothesis that scent-marking has a territorial and sexual connotation and that in the enclosures both group behavior and individual uniqueness are evident in the territory marking context. Furthermore, the width of a tree trunk is not an IRM-eliciting marking; rather, the location of the tree is important (i.e., in the context of territorial boundaries).

15.10. CHEMISTRY RELATED TO MF OF THE TIGER AND OTHER BIG CATS

15.10.2. Chemical Analysis of MF

15.10.2.1. Volatile and Nonvolatile Compounds Identified in MF

Van den Hurk (2007) sums up in tabular form much of the findings on pheromones of the small cats and big cats including our results. During the late 1970s, 1980s, and 1990s we primarily isolated different chemical groups on the basis of pH difference during steam distillation from MF, such as free fatty acids (FFAs) in the acidic fraction, 2AP, aldehydes and ketones in neutral fraction, and amines in basic fractions. The fractions were rendered into salt or derivatized according to their functional groups and then subjected to different chromatographic techniques. Most of the compounds were identified by following classical methods and using modern-day instruments (Table 15.3). Burger et al. (2008) identified more compounds from MF of tiger by headspace solid phase microextraction (SPME) GCMS, which has the advantage of direct application to the instrument. The important point to note is that in the tiger volatile free fatty acids (FFAs); (C2-C10), which are known to be pheromones in many mammals, comprise only branched and unbranched FFAs; no unsaturated and antiso FFAs have been identified in tiger MF (Figures 15.7 and 15.8a, b; Table 15.3). Primary, secondary, and tertiary amines as well as carbonyl compounds were identified in MF of tigers. β-phenylethylamine was detected in MF of four tigers and in MF of leopard and cheetah (Figure 15.9). β-phenylethylamine may be a common urinary excretory product but it was interesting to note its role in depressed persons and fierce criminals (Brahmachary and Dutta 1981). Van den Hurk (2007) reevaluated the importance of β-phenylethylamine in this context.

TABLE 15.3

Volatile Compounds Identified from MF of Tiger, Leopard, Cheetah, and Lion

FIGURE 15.7

Gas chromatogram of free fatty acids identified from MF of tiger (M1). Peak No. 1 = acetic acid, 2 = propionic acid, 3 = isobutyric, 4 = butyric, 5 = isovaleric acid, 6 = valeric, 7 = isohexanoic, 8 = hexanoic, 9 = isoheptanoic, 10 = heptanoic, 11 = isooctanoic, (more...)

FIGURE 15.8

(a) Mass fragments of octanoic acid identified from the acidic fraction of steam distillate of MF of the tiger. (b) Mass fragments of isovaleric acid identified from acidic fraction of steam distillate of MF of the tiger.

FIGURE 15.9

Gas chromatogram of amines present in MF of the cheetah. Peak numbers: 1 = ethylenediamine, 2 = putresceine, 3 = cadaverine, 4 = β-phenylethylamine. Column: 10% Carbowax 20M + 5% KOH (3m × 3mm) packed stainless steel metal column, program: (more...)

Aldehydes and ketones have not been detected in cheetah MF although these have been identified in the tiger and leopard (Figure 15.10). In the context of genomics and metabolomics, we also mention the findings on cheetah MF. Unfortunately we could work only on a single cheetah, a subadult almost attaining the adult stage, but if this is indeed a characteristic chemical feature of the cheetah (as opposed to that of the tiger, lion, and leopard), then we face a question that is intriguing per se. Moreover, it has a bearing on the problem of metabolomics. This fact might be exploited while studying the genomics of the different cat species—and the cheetah is an unusual member of the cat family—and furthermore, while considering the putative differences in MF at the species level (see Section 15.8 for details).

FIGURE 15.10

Mass fragments of acetaldehyde-2,4 dinitrophenyl-hydrazone derivatized from the neutral fraction of steam distillate MF of the tiger. After derivatization the sample was purified through thin-layer chromatography before subjected to gas chromatography. (more...)

15.10.2.1.1. 2AP: The Elusive Aroma Molecule of Tiger MF, Basmati Rice, Bassia Flower, and a Certain Pulse (Mung Bean)

In 1982 this aroma molecule 2AP was identified in boiled Basmati rice (Buttery et al. 1982) and the next year it was detected in the leaves of Pandanus amaryllifolius (Roxb. = P. faetoedus; family: Pandanaceae) by Buttery’s group (Buttery et al. 1983). This plant was long known as producing a smell equivalent to that of fragrant rice and in Bengal it was locally known as Payes leaf. In 1977 Brahmachary and Dutta detected this aroma from MF of the pet tigress Khairi and noticed that on acidification of MF, fragrant rice water, and P. amaryllifolius Roxb. leaf extract the aroma disappears but it reappears as the fluid is rendered alkaline, and they had an inkling that the three fragrance molecules have some chemical similarity and that civetone, which also has a ricelike fragrance, must be different from the rice/tiger aroma (Brahmachary and Dutta 1979, unpublished note). In the 1980s and 1990s a large number of experiments with paper chromatography (PC) and gas chromatography (GC), using two solvents and two GC columns and cochromatography of GC, indicated the closely similar nature of rice aroma and tiger aroma (Brahmachary et al. 1990). Later comparisons with a synthetic sample gifted by Schieberle revealed that the tiger aroma is in fact 2AP (Brahmachary 1996). Schieberle (1985) synthesized 2AP following an easy technique based on the Maillard reaction (MR) at a temperature of 170°C and our group could bring it down to 128°C–135°C (Poddar-Sarkar et al. 1992) and ultimately to 105°C but no less (Poddar-Sarkar et al. 1993, unpublished). The biosynthesis of 2AP in rice may be enzymatic by a metabolic process within the system and not by MR. Stable isotope labeling (C¹³ and C¹⁵) shows that the nitrogen of 2AP is derived from proline but the carbon source of the acetyl group is some other molecule and that the reaction occurs at a lower temperature than required for MR (Yoshihashi et al. 2002). 2AP was also detected in flowers of Bassia latifolia Roxb. = Maduca indica (local name Mahua) (Midya and Brahmachary 1997), in flowers of Vallaris solanacea (Basu et al. 2007), and is also a component of a fragrant pulse of Bengal (local name Sona Mung) (Brahmachary and Ghosh 2002). However, Burger et al. could not confirm the presence of 2AP in Bengal tiger MF. Apps reports no 2AP smell in African leopard (Brahmachary 2013, personal communication). We have detected 2AP in the MF of the Siberian tiger when the sample was available to us under an Indo-U.S. exchange program (Soso et al. 2012). The characteristic smell is absent in adult African lions and cubs and adult Asiatic lions and an almost adult cheetah (free-ranging adult African lions and cubs introduced into nature for a few hours every day at Kampi ya Simba, George Adamson’s camp at Kora, Kenya, and a big cub in captivity at Lulimbi, Zaire, were the source of MF and urine in this context. The Asiatic adult lions in captivity in the heart of the forest in Gir, India, and an almost adult cheetah free-ranging in about 10,000 square meter in Namibia were observed).

Our findings on the presence of 2AP, the most uncommon compound among many candidates for pheromones present in both MF and urine of both the sexes of tiger and Indian leopard (but not in lion and cheetah), might project a new line of thought for understanding the two distinct phylogenetic clades of the cat family. The tiger and the leopard, rather than the lion, might be near neighbors because of the metabolite 2AP. This aspect of metabolomics can indirectly shed light on the relevance of genomics to tiger pheromone. As already mentioned we have recently traced 2AP in the Siberian tiger (Soso et al. 2012) and also in the so-called marsh mangrove tiger of the Sunderbans, a race of the Bengal tiger (Poddar-Sarkar and Brahmachary 2012, unpublished). Since, as mentioned above, the Siberian/Amur race is significantly different from the Bengal tiger, 2AP in the tiger is probably of ancient origin. In that case the presence of 2AP in the marsh tiger, a recent adaptation in the Sundarban mangrove swamp is not surprising (Figure 15.11).

FIGURE 15.11

Tranquillized mangrove–marsh Bengal tiger of Sundarban being released back to nature after collection of sample for GCMS for the analysis of chemical compounds of body odor. (Photo courtesy of Subroto Pal Chowdhury.)

It would be of interest to investigate the presence of 2AP in the Chinese and Sumatran races. In our views, the origin of this significant aroma molecule may be helpful for tracing the tiger lineage.

15.11. REVIEW AND CONCLUSIONS: FIFTY YEARS OF PHEROMONE RESEARCH OF BIG CATS

The study of pheromones of big cats is undoubtedly one of the more difficult or less tractable propositions but as we have endeavored to show, since 1964, we have made considerable headway. The lacunae in the field have also been discussed. The question of pheromone-based individual recognition is a formidable one in any mammal and it is compounded by the practical difficulties implicit in investigations on big cats. But nonetheless, we feel we can answer some of the basic questions. It transpires from our attempts that the major source of pheromones in big cats is the MF and this is an ensemble of various chemical compounds.

As concluding remarks we may sum up the process of understanding MF chronologically. Around 1960 the concept of pheromones in big cats emerged apparently in the widely read popular accounts of Joy Adamson on Elsa the lioness and later on Pippa the cheetah. During the late 1960s Schaller (1967) brought it to the attention of scientists and hinted at the possibility of decoding the information encoded in this message. For a long time after Schaller described MF spray as a mixture of urine and anal gland secretion, this misconception continued to persist in the scientific literature, even as late as 2006 (Thapar 2006). We have described a mass of evidence (from the early 1980s to 2013) suggesting that MF has evolved to meet a purpose—to communicate with conspecific neighbors—for otherwise, this loss of energy (including, in particular, throwing away a large amount of lipids that are metabolically costly) would have been selected against through the evolutionary time scale. However, compared to the tigress and female serval all other female cats spray rarely, only during pro- or early estrous but all urinate significantly more during or before estrous. In addition, the related facts of different modalities of MF spray and urination in different big cat families like the tiger, lion, cheetah, and leopard were reported during the 1980s in several papers (Brahmachary and Dutta 1981, 1986, 1987). An analogy in the plant world can be drawn if we consider root exudates, the plant equivalent of excretory products like urine, MF, and feces of the big cats or other animals. Likewise certain leaf volatiles are the equivalent of animal body odor.

Around the 1980s and 1990s, in a number of papers Brahmachary, Dutta, and Poddar-Sarkar detected 30–40 compounds in the tiger, and similar types of compounds in the cheetah, leopard, and lion MF and an unusual molecule 2AP in the tiger and leopard only (Brahmachary et al. 1990; Poddar-Sarkar and Brahmachary 2004; Poddar-Sarkar et al. 1995; Brahmachary, 1996). Andersen and Vulpius (1999) identified several volatile compounds from zoo lions. Burger et al. (2008) identified more than 100 compounds in a zoo tiger MF, with the help of headspace SPME-GCMS, but they failed to find 2AP. We have meanwhile detected 2AP in the marsh-mangrove tiger of the Sunderbans, India (Poddar-Sarkar and Brahmachary 2011, unpublished) and also in the Siberian tiger in 2012 (Soso et al. 2012). Chemical analysis of MF of the cheetah and leopard have been reported as mentioned earlier. McLean’s group highlighted the presence of cauxin protein in urine (McLean et al. 2007). Proteomics- and genomics-related work for tracing the phylogeny of big cats was carried out by several schools in recent years. (In Section 15.8 we discussed the genomics-related work as well as the metabolomics perspective.) Preliminary findings on the body odor of three tranquilized mangrove-marsh Bengal tigers of Sundarban were reported in 2013 (Poddar-Sarkar et al. 2013).

Most or all mammals rely on olfactory signals and this ability must have evolved early in the evolutionary history. Even an E. coli bacterium is attracted to certain molecules like amino acids in the medium that are associated with decaying matter indicating a food source.

More specifically, we may try to answer some of the questions raised by Tinbergen’s remarks in Section 15.2. What exactly is the survival value of the instinct of spraying MF by big cats? This was the first query of Tinbergen. The answer in popular terms would be “waste not, want not.” Such is nature’s economy that nothing is wasted. Materials like scats, urine, or MF rejected by the body are not necessarily wasted (true, some of these substances may be utilized as food by other organisms ranging from bacteria but here we are concerned only with the benefit to the big cats themselves). MF, as we have seen, plays a vital role in attracting the opposite sex, thereby ensuring reproduction, a vital issue, and proclaiming a territory. In a sense this material ejected from the body may be considered as an extended phenotype and have a great survival value.

Likewise, the second and third questions of Tinbergen (namely, how has MF developed over time and how has it developed in the individual?) are also amenable to the evolutionary perspective. As we have mentioned earlier, Darwin suggested that “…if the more odoriferous males are the most successful in winning over females….” then natural (in this case sexual) selection would lead to the evolution of the trait (sending this odor signal). This would be equally valid for the females and their olfactory abilities. This might answer both the second and third questions.

The fourth question (What is the physiological causation?) is more difficult to address at present. We do not know exactly how the lipid is generated in the urine of MF and by which metabolic pathway, or how an unusual molecule like 2AP arises. But production of these metabolites and their excretion is not against the laws of physiology.

15.12. MANY UNSOLVED PROBLEMS

• 1. We have as yet no inkling of the natural chemicals that undoubtedly send signals to the VNO of the tiger. These must be relatively heavy molecules with little volatility. These might be proteins like aphrodisin, cauxin, or other, totally different molecules. That the VNO is very active in the big cats is well evident through frequent flehmen gestures and touching the nostril with the tongue, though in this respect the big cat tongue is far more ill-adapted than the bifurcated narrow tongue of snakes or Varanus (monitor lizard).
• 2. We have to cross another hurdle regarding the recognition of an individual-specific set of pheromones(s) or osmic signals. Despite the possibility of individual recognition based on an ensemble of a number of chemical compounds that vary quantitatively in the different individuals, as explained earlier, a tricky question arises. The fading of the more volatile compounds convey information to the big cat, namely that a rival/intruder left the site some time ago and so there is no immediate concern/fear/stress; but can the animal perceive whether it is its own old mark or that of another? This question arises because (a) the degree of fading, or in other words, the intensity of disappearance of many molecules depends on several environmental and climatic factors, and (b) the lesser the number of different molecules in the pheromonal potpourri, the more difficult it is to distinguish “individuality.”
• 3. Again, even though the tiger might distinguish a lion’s smell (formerly the lion and the tiger coexisted in many parts of India) because of the absence of 2AP, can it possibly have any inkling that a leopard is different from a tiger? All the currently known pheromones are chemically the same in both species and so despite quantitative differences a leopard may be perceived as another tiger. Observational results cannot answer the question because both intruders will be repelled by the resident tiger. There should be species-specific ratios of chemical compounds or some other mechanism of which we have no insight at present. One may legitimately ask which of the many putative candidates for pheromones are actually functional as pheromones. Apps et al. (2013) have accepted this challenging task with the hundred-odd urinary compounds of the African wild dog. They point out that many compounds such as carboxylic acids are common in sympatric species and so unlikely to be species-specific pheromones and therefore unique compounds should claim priority in this context. They have gone far along this line but we feel that because of essential genetic/physiological/biochemical reasons every species may not have specific, unique compounds in their urine, MF, glandular secretions, and so forth (we have, however, previously discussed the possibility of bile salts in scat characteristic for each species). On the other hand, the quantitative proportions of different carboxylic acids distinguish the individuality of the animal, as we have already noted. Might not such ratios and proportions characterize species as well? In a later personal communication by Apps, certain difficulties are evident. The data on the lion, leopard, and cheetah are still scant and his group detected no aldehyde or ketone even in the leopard or lion. Furthermore, they also did not detect 2AP in the African leopard. We will discuss elsewhere the possible reasons for these results but at the moment, neither we nor they can state how the sympatric big cats might be distinguished at the pheromonal level.
  Voznessenskaya et al. (1992) point out that rats find it increasingly difficult to distinguish among more than 5–6 individual odors in a mixup. Even if they can distinguish only 5–6 individual odors, the same faculty might help the animals to distinguish 5–6 sympatric species and that would suffice in most cases.
• 4. A tiger overmarks the marking of an intruder and if the latter does not decamp immediately, the first tiger may sooner or later overmark the overmarking. In the case of certain rodents there is some evidence that they can detect the difference between the top and bottom overmarking. There is evidence that the animal marking on top enjoys an advantage. It has been shown that a third animal can distinguish the two (Ferkin and Pierce 2007, 2010). Even in a mixture of urine of 6–7 mongoose individuality was distinguishable (Jordan et al. 2011). Therefore, it is in the interest of the resident to overmark once again. How the rodent or mongoose or the tiger can perceive this is a well-nigh incredible phenomenon.

ACKNOWLEDGMENTS

We are indebted to George Schaller, George Adamson, P. Amte and their colleagues, and many zoo authorities, private reserves, and keepers who have been associated with the big cats for many years in India and Africa. We are grateful to the-then Prime Minister of India Mrs. Indira Gandhi for her kind help for sanctioning a special grant for tiger research from the Department of Environment, the Government of India at Indian Statistical Institute, Calcutta, and also to other funding agencies of the Government of India like the Council of Scientific and Industrial Research and University Grant Commission. We are grateful to Prof. D. Muller Schwarze and Prof. Francis Webster of State University of New York, Syracuse, who extended their kind help for running our sample in GCMS in 1991 for free fatty acids. We extend our sincere thanks to Prof. Barbara Sommerville of Cambridge University and Prof. J. Waterhouse of Anglia Polytechnic, Cambridge, for their help with sniff GC in 1992 and valuable suggestions and critical review from time to time. RLB thanks Sally Walker, Sarada Mallya, Sabita Rai, and Katyaani of Mysore. MPS is thankful to her cofield worker Prof. S. S. Sarkar (her geologist husband) and her photographer friend Dr. N. Das during many field sessions. We acknowledge the kind help from our many collaborators and many reviewers for giving a definite shape to our findings. Surendranath College, Calcutta, University of Calcutta are gratefully acknowledged for extending infrastructural facilities. We appreciate the continuous inspiration and criticism coming from our research scholars including our American guest student Simone Soso, who participated in many constructive and stimulating discussions. We thank Dilip Bhattacherya from whose collection we obtained the photograph of Khairi, the pet tigress of Simlipal, who initiated scientific research on tiger pheromones and other behavioral aspects (Figure 15.12). We express our sincere gratitude to the late Mr. Saroj Raj Choudhuri and Ms. Nihar Nalini-who tamed Khairi- S. K. Patnaik, Director at Nandan Kanan Biological Park, Dr. L. N. Acharjo, veterinarian, Nandan Kanan and Shib Mohanti, Jibonaloke (who raised Dora III), office staff of Nandan Kanan; our many animal lover friends, and S. B. Mondal, Principal Chief Conservator of Forest, Government of West for kindly giving us permission. We thank Dr. E. Ali, Dr. Asish Sen, and the late Dr. P. Bhattyacharya of the Indian Institute of Chemical Biology, Kolkata, and Prof. Sibdas Ray, Department of Chemistry, University of Calcutta (CU). MPS is grateful to the Hon’ble Vice Chancellor (CU), Pro-VC and Registrar, CU for giving her permission to participate in Indo-US, 2011 and Indian National Science Academy-Hungary Academy of Science Bilateral Exchange Programme, 2012. We are indebted to many contributors during our four-decades-long study—our two pet tiger cubs Dora II and Dora III and many tigers and tigresses of Nandan Kanan, and Bipasa, the tigress of South Khairabari, North Bengal—who are no longer with us.

FIGURE 15.12

‘Khairi’ with her human mother (Ms. Nihar Nalini) and Mr. Dilip Bhattacherya. (From the collection of Mrs. Susmita Ghosh, Salt Lake, Calcutta.)

REFERENCES

• Adamson G. My Pride and Joy. Collins; London: 1986.
• Adamson J. Born Free. Collins; London: 1960.
• Albone E. Mammalian Semiochemicals. John Wiley; Chichester, United Kingdom: 1984.
• Andersen K.F, Vulpius T. Urinary volatile constituents of the lion. Chem. Senses. 1999;24:179–189. [PubMed: 10321819]
• Anderson M.B. Sexual Selection. Princeton University Press; Princeton, NJ: 1994.
• Apps P, Mmualefe L, McNutt J.W. A reverse engineering approach to identifying which compounds to bioassay for signaling activity in the scent marks of African wild dogs (Lycanon pictus). In: East M.L, Dehnhard M, editors. In Chemical Signals in Vertebrates 12. Springer; New York: 2013.
• Asa C.S. Relative contributions of urine and anal-sac secretions in scent marks of large felids. Amer. Zool. 1993;33:167–172.
• Bailey T.N. The African Leopard: A Study of the Ecology and Behavior of a Solitary Felid. Columbia University; New York: 1993.
• Baker E.B. Sport in Bengal. Ledger, Smith & Co; London: 1887.
• Baker W, Deem S, Hunt A, Munson L, Johnson S. Jaguar species survival plan. In: Law C, editor. In Guidelines for Captive Management of Jaguars. 1/1. Jaguar Species Survival Plan Management Group; Forth Worth, TX: 2002. pp. 9–13.
• Bank G.R, Buglass A.J, Waterhouse J.S. Amines in the marking fluid and anal sac secretion of the tiger. Panthera tigris. Z. Naturforsch C. 1992;47((7–8)):618–620. [PubMed: 1388518]
• Barja I, Miguel F.J. Chemical communication in large carnivores: Urine-marking frequencies in captive tigers and lions. Pol. J. Ecol. 2010;58((2)):397–400.
• Barnett S.A. Modern Ethology: The Science of Animal Behavior. Oxford University Press; New York: 1981.
• Basu S, Mitra K, Pal A, and D.C, Datta J, editors. Encyclopedia of Himalayan Medicinal Flora. Vol. 3. Horticulture Development Foundation; Kolkata: 2007.
• Berglund H, Lindström P, Savic I. Brain response to putative pheromones in lesbian women. Proc. Natl. Acad. Sci. U. S. A. 2006;103((21)):8269–8274. [PMC free article: PMC1570103] [PubMed: 16705035]
• Bertram B.C.R. Social system of lions. Sci. Am. 1975;232:54–65.
• Bhattacharjee S, Mallik P.K, Shekhawat R.S, Anoop K.R, Sankar K. Tale of a travelling tiger. Sanctuary Asia. 2012 June;XXXIII((3))
• Bininda-Emonds O.R.P, Decker-Flum D.M. The utility of chemical signals as phylogenetic characters; an example from the felidae. Biol. J. Linn. Soc. Lond. 2001;72:1–15.
• Bland K.P. Tomcat odour and other pheromones. Vet. Sci. Commun. 1979;3:125–136.
• Börger L, Dalziel B.D, Fryxell J.M. Are there general mechanisms of animal home range behaviour? A review and prospects for future research. Ecol. Lett. 2008;11:637–650. [PubMed: 18400017]
• Brahmachari G.K, Brahmachary R.L. Mimeo note on olfaction in the tiger; Calcutta, India: 1980.
• Brahmachary R.L, Dutta J. Phenylethylamine as a biochemical marker of tiger. Z. Naturforsch C. 1979;34:632–633. [PubMed: 158904]
• Brahmachary R.L, Dutta J. On the pheromones of tigers: Experiments and theory. Am. Nat. 1981;118:561–567.
• Brahmachary R.L, Dutta J. Pheromones of leopards: Facts and theory. Tiger Paper. 1984;II((3)):18–23.
• Brahmachary R.L. Ecology and chemistry of mammalian pheromones. Endeavour. 1986;10((2)):65–68. [PubMed: 2426081]
• Brahmachary R.L, Dutta J. Chemical communication in the tiger and leopard. In: Tilson R.L, Seal U.S, editors. In Tigers of the World: The Biology, Biopolitics, Management, and Conservation of an Endangered Species. Noyes Publications; Park Ridge, NJ: 1987.
• Brahmachary R.L. 1990. Final report (Mimeo) on “Chemical and ecological aspects of pheromones of the tiger,” submitted to Department of Environment, Govt. of India.
• Brahmachary R.L, Poddar-Sarkar M, Dutta J. The aroma of tiger...and rice. Nature. 1990;344:26. [PubMed: 18278014]
• Brahmachary R.L, Dutta J, Poddar-Sarkar M. The marking fluid of the tiger. Mammalia. 1991;55((1)):150–152.
• Brahmachary R.L, Poddar-Sarkar M, Dutta J. Chemical signal in the tiger. In: Muller-Schware D, Doty R.L, editors. In Chemical Signals in Vertebrates 6. Plenum Press; New York: 1992. pp. 477–479.
• Brahmachary R.L, Poddar-Sarkar M, Dutta J. Evolution of chemical signals. In: Majumdar P.P, editor. In Human Population Genetics. Plenum; New York: 1993.
• Brahmachary R.L. The expanding world of 2-acetyl-1-pyrroline. Curr. Sci. 1996;71:257–258.
• Brahmachary R.L, Singh M, Rajput M. Scent marking in the Asiatic Lion. Curr. Sci. 1999;78((2)):480–481.
• Brahmachary R.L, Singh M. Behavioral and chemical aspects of scent marking in the Asiatic lion. Curr. Sci. 2000;78((6)):680–682.
• Brahmachary R.L, Ghosh M. Vaginal pheromone and other compounds in mung bean aroma. J. Sci. Industr. Res. 2002;61:625–629.
• Brahmachary R.L. Animal Behaviour. Naturism; Kolkata: 2011.
• Brennan P.A. MHC associated chemosignals and individual identity. In: Hurst J.L, Beynon R.J, Roberts S.C, Wyatt T.D, editors. In Chemical Signals in Vertebrates 11. Springer; New York: 2008. pp. 131–140.
• Broekhuis F. Habitat selection patterns of cheetahs. In: Tanzania Serengeti M.Sc., editor. Acinonyx jubatus. The Royal Veterinary College; University of London: 2007. in the. research project.
• Burger B.V, Viviers M.Z, Bekker P.I, le Roux M, Fish N, Fourie W.B, Weibchen G. Chemical characterization of territorial marking fluid of male Bengal tiger. Panthera tigris. J. Chem. Ecol. 2008;34:659–671. [PubMed: 18437496]
• Burt W.H. Territoriality and home range concepts as applied to mammals. J. Mammal. 1943;24:346–352.
• Buttery R.G, Ling L.C, Juliano B.O. 2-acetyl-1-pyrroline: An important aroma component of cooking rice. Chem. Indus. 1982;4:958–959.
• Buttery R.G, Ling L.C, Juliano B.O, Turnbaugh J.C. Cooked rice aroma and 2-acetyl-1-pyrroline. J. Agric. Food Chem. 1983;31:823–826.
• Caro T.M, Collins D.A. Ecological characteristics of territories of male cheetahs (Acinonyx jubatus). J. Zool. Lond. 1987;211:89–105.
• Caro T.M. University of Chicago: 1994. Cheetahs of the Serengeti plains: Group living in an asocial species. Ph.D. thesis.
• Carrington-Turner J.E. Man-Eaters and Memories. Jaico; Bombay, India: 1959.
• Chandawat R.S. Great cats of India. TV episode (as consultant): Animal Planet; 2002.
• Chandawat R.S. Tigers of Dry Forest: Do they have enough space to survive? In: Thaper V, editor. In Tiger: The Ultimate Guide. Oxford University Press; New Delhi: 2006.
• Chellam R. Ecology of Asiatic lion. Rajkot: Saurashtra University; 1993. Ph.D thesis.
• Chong A.Y.Y. Orbit: The University of Sydney Undergraduate Research Journal. (1) Vol. 1. 2009. Genetic variation in the MHC of the Collared peccary: A potential model for the effects of captive breeding on the MHC; pp. 98–116.
• Choudhury S.R. Khairi, the Beloved Tigress (posthumously published). Natarajan Publisher; Dehra Dun, India: 1999.
• Claesson A, Silverstein R.M. Chemical methodology in the study of mammalian communications. In: Müller-Schware D, Mozell M.M, editors. In Chemical Signals in Vertebrates. Plenum Press; New York: 1977. pp. 71–93.
• Cracraft J, Feinstein J, Vaughan J, Helm-Bychowski K. Sorting out tigers (Panthera tigris): Mitochondrial sequences, nuclear inserts, systematics and conservation genetics. Anim. Conserv. 1998;1:139–150.
• Corbett J. Man-Eaters of Kumaon. Oxford University Press; Bombay: 1944.
• Corbett J. The Temple Tiger. Oxford University Press; India: 1954. 1988. Reprinted by.
• Darwin C. The Descent of Man. D. Appleton & Co; New York: 1871.
• Datta S.P, Harris H. A convenient apparatus for paper chromatography; results of a survey of the urinary amino-acid patterns of some animals. J. Physiol. (Lond.). 1951;114:39–41. [PubMed: 14874231]
• Davis B.W, Li G, Murphy W.J. Supermatrix and species tree methods resolve phylogenetic relationships within the big cats. Panthera (Carnivora: Felidae) Mol. Phylogenet. Evol. 2010;56:64–76. [PubMed: 20138224]
• Dawkins R. The Extended Phenotype. Oxford University Press; Oxford: 1983.
• De P.K. Sex hormonal regulation of 20.5 and 24 kDa major male-specific proteins in Syrian hamster submandibular gland. J. Steroid. Biochem. Mol. Biol. 1996;58((2)):183–187. [PubMed: 8809199]
• Driscoll C.A, McDonald D, and W, O’Brien S.J. From wild animals to domestic pets, an evolutionary view of domestication. PNAS. 2009;106:9971–9978. [PMC free article: PMC2702791] [PubMed: 19528637]
• Dunbar Brander A.A. Wild Animals in Central India. E. Arnold; London: 1923.
• Dunbar J. Tigers, Durbars and Kings: Fanny Eden’s Indian Journals, 1837–1838. John Murray Publishers; London: 1989.
• Eaton R. The Cheetah: The Biology, Ecology and Behavior of Endangered Species. Van Nostrand and Reinhold; New York: 1974.
• Eden F. Tigers, Durbars and Kings: Fanny Eden’s Indian Journals. 1837–1838
• Estes R.D. The role of vomeronasal organ in mammalian reproduction. Mammalia. 1972;36:315–341.
• Ewer R.F. Ethology of Mammals. Elek Science; London: 1968.
• Ewer R.F. Carnivores. Weidenfeld and Nicholson; London: 1973.
• Ewert J.P, Traud R. Releasing stimuli for antipredator behavior in common toad. Bufo bufo. Behaviour. 1979;68:170–180.
• Fayer J. The Royal Tiger of Bengal: His Life and Death. J & A Churchill; London: 1875.
• Ferkin M.H, Pierce A.A. Perspectives on over-marking: Is it good to be on top? J. Ethol. 2007;25:107–116.
• Ferkin M.H, Ferkin A, Ferkin B.D, Vlautin C.T. Olfactory experience affects response of meadow voles to the opposite-sex scent donor of mixed-sex overmarks. Ethology. 2010;116:821–831. [PMC free article: PMC2914329] [PubMed: 20694044]
• Forsyth J. The Highlands of Central India. Chapman and Hall; London: 1872.
• Gorman M.L, Nedwell D.B, Smith R.M. An analysis of contents of anal scent pockets of Herpestes. J. Zool. Lond. 1974;172:384.
• Gorman M.L. A mechanism for individual recognition by odour in Herpestes. Anim. Behav. 1976;24:141.
• Graham C. Menstrual synchrony: An update and review. Hum. Nat. 1991;2((4)):293–311. [PubMed: 24222338]
• Hashimoto Y, Eguchi Y, Arakawa J.A. Historical observation of the anal sac and its glands in a tiger. Jap. J. Vet. Sci. 1963;25:29–32.
• Hediger H. Ethology and study of animals in captivity. In: Grzimek B, editor. In Grzimek’s Encyclopedia of Ethology. Van Nostrand and Reinhold; London: 1977.
• Heinsohn R. Group territoriality in two populations of African lions. Anim. Behav. 1997;53:1143–1147. [PubMed: 9236011]
• Hemker T.P, Lindzey F.G, Ackerman B.B. Population characteristics and movement patterns of cougars in Southern Utah. J. Wildl. Mgmt. 1984;48:1275–84.
• Hemmer H. Untersuchungen zur Stammesgeschichte der Pantherkatzen 839 (Pantherinae). Teil III. Zur Artgeschichte des Löwen, Panthera leo (Linnaeus 1758). Veröffentlichungen der Zoologischen Staatssammlung. 1974;17:167–280.
• Hendriks W.H, Moughan P.J, Tarttelin M.F, Woolhouse A.D. Felinine: A urinary amino acid of Felidae. Comp. Biochem. Physiol. B. 1995;112:581–588. [PubMed: 8590373]
• Hewer T.F, Matthews L.H, Malkin T. Lipuria in tigers. Proc. Zool. Soc. Lond. 1948;118:924–928.
• Horonecker M. An analysis of mountain lion predation upon mule deer and elk in the Idaho primitive area. Wildl. Monogr. 1970;21:1–39.
• Houser A, Somers M.J, Boast L.K. Home range use of free-ranging cheetah on farm and conservation land in Botswana. S. Afr. J. Wildl. Res. 2009;39((1)):11–22.
• Howard H.E. Territory in Bird Life. John Murray Publishers; London: 1992.
• Hurst J.L, Payne C.E, Nevison C.M, Marie A.D, Humphire R.E, Robertson D.H, Cavaggioni A, Beynon R.J. Individual recognition in mice mediated by major urinary proteins. Nature. 2001;414:631–634. [PubMed: 11740558]
• Ilany G. The leopard of the Judean desert. Israel Land. Nat. 1981;6:59–71.
• Inglis J. Tent Life in Tigerland, with which Is Incorporated Sport and Work in the Nepaul Frontier. Sampson Low; Marston, and Co., London: 1892.
• Jackman B, Scott J, Scott A. The Marsh Lions: The Story of an African Pride. Elm Tree Books; London: 1982.
• Jackson R, Ahlborn G. Snow leopards (Panthera uncia), in Nepal-home-range and movements. Nat. Geogr. Res. 1989;5((2)):161–175.
• Jeffery K.J.M, Bangham C.R.M. Do infectious diseases drive MHC diversity? Microbes Infect. 2000;2:1335–1341. [PubMed: 11018450]
• Johnson W.E, Dratch P.A, Martenson J.S, O’Brien S.J. Resolution of recent radiations within three evolutionary lineages of Felidae using mitochondrial restriction fragment length polymorphism variation. J. Mammal. Evol. 1996;3:97–120.
• Jordan N.R, Mwanguhya F, Kyabulima S, Rüedi P, Hodge S.J, Cant M.A. Scent marking in wild banded mongooses: Intrasexual overmarking in females. Anim. Behav. 2011;81:51–60.
• Kelley J, Walter R, Trowsdale J. Comparative genomics of major histocompatibility complexes. Immunogenetics. 2005;56:683–695. [PubMed: 15605248]
• Locke A. Tigers of Trengganu. Museum Press; London: 1954.
• Li G, Janecka J.E, Murphy W.J. Accelerated evolution of CES7, a gene encoding a novel major urinary protein in the cat family. Mol. Biol. Evol. 2011;28:911–920. [PubMed: 20966115]
• Lyddeker R, editor. The Royal Natural History. Frederick Warne; London: 1894.
• Manning A, Stamp Dawkins M. An Introduction to Animal Behaviour. Cambridge University Press; Cambridge: 1992.
• Maser C, Mate B.R, Franklin J.F, Dyrness C.T. Natural history of Oregon coast mammals. USDA Forest Service, Forest Service, Pacific Northwest Forest and Range Experiment Station. General Technical Report PNW. 1981:133.
• Mathews L.H. The Life of Mammals. Weidenfeld and Nicholson; London: 1969.
• Maynard Smith J, Harper D.G.C. The evolution of aggression: Can selection generate variability? Phil. Trans. R. Soc. Lond. B. 1988;319:557–570. [PubMed: 2905492]
• McBride C. The White Lions of Timbavati. Paddington Press; New York: 1977.
• McBride C. Operation White Lion. St Martin’s Press; New York: 1981.
• McClintock M. Menstrual synchrony and suppression. Nature. 1971;229:244–245. [PubMed: 4994256]
• McClintock M.K, Stern K. Regulation of ovulation by human pheromones. Nature. 1998;392((6672)):177–179. [PubMed: 9515961]
• McDougal C.W. The Face of the Tiger. Rivington and Krutsch; London: 1977.
• McLean L, Hurst J.L, Gaskell J.C, Lewis J.C.M, Beynon R.J. Characterization of cauxin in the urine of domestic and big cats. J. Chem. Ecol. 2007;33((10)):1997–2009. [PubMed: 17924168]
• Michael R.P, Bonsall R.W, Warner P. Human vaginal secretions volatile fatty acid content. Science. 1974;186:1217–1219. [PubMed: 4432068]
• Midya S, Brahmachary R.L. The aroma of Bassia flower. Curr. Sci. 1996;71((6)):430.
• Midya S, Brahmachary R.L. A method of producing basmati rice aroma from Bassia latifolia flowers. IRRN. 1997;22:21.
• Mills M.G.L. Comparative behavior and ecology of hyenas. In: Gittelman J.L, editor. In Carnivore Behavior, Ecology and Evolution. Cornell University Press; Ithaca, NY: 1989.
• Mills M.G.L. The lion (Panthera leo) and cheetah (Acinonyx jubatus) in Kruger National Park, South Africa. Felid. 1990;4((1)):13.
• Miquelle D, Arzhanova T, Solkin V, editors. Vladivostok, Russia: USAID Russian Far Eastern EPT Project; 1996. A recovery plan for conservation of the Far Eastern leopard: Results of an international conference held in Vladivostok, Russia.
• Mitchell M.S, Powell R.A. A mechanistic home range model for optimal use of spatially distributed resources. Ecol. Model. 2004;177:209–232.
• Miyazaki M, Yamashita T, Suzuki Y, Saito Y, Soeta S, Tiara H, Suzuki A. Major urinary protein of the domestic cat regulates the production of felinine, a putative pheromone precursor. Chem. Biol. 2006;13:1071–1079. [PubMed: 17052611]
• Miyazaki M, Yamashita T, Taira H, Suzuki A. The biological function of cauxin, a major urinary protein of the domestic cat. In: Hurst J.L, Beynon R.J, Roberts S.C, Wyatt C, editors. In Chemical Signals in Vertebrates 11. Springer; New York: 2008.
• Montgomery S. Spell of the Tiger. Houghton Mifflin; Boston: 1995.
• Mooney N. Tasmanian tiger sighting. Aust. J. Nat. Hist. 1984;21:177–180.
• Mosser A, Packer C. Group territoriality and the benefits of sociality in the African lion. Panthera leo. Anim. Behav. 2009;78:359–370.
• Mountfort G. Saving the Tiger. Viking Press; New York: 1981.
• Muntifering J.R, Dickman A.J, Perlow M.L, Hruska T, Ryan P.G, Marker L.L, Jeo R.N. Managing the matrix for large carnivores: A novel approach and perspective from cheetah (Acinonyx jubatus) habitat suitability modelling. Anim. Conserv. 2006;9:103–112.
• Nordlund D.A, Lewis W.J. Terminology of chemical releasing stimuli in intraspecific and interspecific interactions. J. Chem. Ecol. 1976;2:211–220.
• Novotny M.V. Pheromones, binding proteins and receptor responses in rodents. Biochem. Soc. Trans. 2003;31:117–122. [PubMed: 12546667]
• Nowak R.M. Walker’s Mammals of the World. II. Johns Hopkins University Press; Baltimore, MD: 2010.
• O’Brien S.J, Wildt D.F, Bush M. The cheetah in genetic peril. Sci. Am. 1986;254:84–92.
• O’Brien S.J, Yuhki N. Comparative genome organization of the major histocompatibility complex: Lessons from the Felidae. Immunol. Rev. 1999;167:133–144. [PMC free article: PMC7165862] [PubMed: 10319256]
• Packer C, Scheel D, Pusey A.E. Why lions form groups: Food is not enough. Am. Nat. 1990;136:1–79.
• Packer C, Kosmala M, Cooley H.S, Brink H, Pintea L, Garshelis D, Purchase G, Strauss M, Swanson A, Balme G, Hunter L, Nowell K. Sport hunting, predator control and conservation of large carnivores. PLoS ONE. 2009;4((6)):e5941. [PMC free article: PMC2691955] [PubMed: 19536277]
• Palagi E, Dapporto L. Beyond odor discrimination: Demonstrating individual recognition by scent in. Lemur catta. Chem. Senses. 2006;31:437–443. [PubMed: 16547195]
• Panwar H.S. Project Tiger: The reserves, the tigers and their future. In: Tilson R.L, Seal U.S, editors. In Tigers of the World: The Biology, Biopolitics, Management, and Conservation of an Endangered Species. Noyes Publications; Park Ridge, NJ: 1987.
• Pelosi P. Odorant-binding proteins: Structural aspects. Ann. N. Y. Acad. Sci. 1998;855:281–293. [PubMed: 9929622]
• Penn D.J. The scent of genetic compatibility: Sexual selection and the major histocompatibility complex. Ethology. 2002;108:1–21.
• Penn D.J. Chemical communication. In: Dicke M, Takken W, editors. In Chemical Ecology: from Gene to Ecosystem. Springer; Dordrecht: 2006.
• Poddar-Sarkar M, Brahmachary R.L, Dutta J. Short chain free fatty acid as a putative pheromone in the marking fluid of tiger. J. Indian Chem. Soc. 1991;68:255–256.
• Poddar-Sarkar M, Sarkar N.D, Dutta J, Brahmachary R.L. A method to synthesize the aroma of certain varieties of fragrant Indian rice. IRRN. 1992;17((5)):9.
• Poddar-Sarkar M. University of Calcutta: 1995. Mammalian semiochemicals: Chemical and behavioural aspects with special reference to tiger. PhD thesis.
• Poddar-Sarkar M. J. Lipid Mediator Cell Signal. Vol. 15. 1996. The fixative lipid of tiger pheromone; pp. 89–101. [PubMed: 9029376]
• Poddar-Sarkar M, Brahmachary R.L. Putative semiochemicals in the African cheetah. J. Lipid Mediat. Cell Signal. 1997;15:285–287. [PubMed: 9041477]
• Poddar-Sarkar M, Brahmachary R.L. Can free fatty acids in the tiger pheromone act as an individual finger print? Curr. Sci. 1999;76((2)):141–142.
• Poddar-Sarkar M, Brahmachary R.L. Putative chemical signals of leopard. Anim. Biol. 2004;54((3)):255–259.
• Poddar-Sarkar M, Chakroborty A, Bhar R, Brahmachary R.L. Putative pheromones of lion mane and its ultrastructure. In: Hurst J.L, Beynon R.J, Roberts S.C, Wyatt T.D, editors. In Chemical Signals in Vertebrates 11. Springer; New York: 2008. pp. 61–67.
• Poddar-Sarkar M, Ray S, Chowdhury P, Samanta G, Brahmachary R.L. On the body odour of wild-caught mangrove marsh Bengal tiger of Sundarban. In: East M.L, Dehnhard M, editors. In Chemical Signals in Vertebrates 12. Springer; New York: 2013.
• Pokorny I, Sharma R, Goyal S.P, Mishra S, Tiedemann R. MHC class I and MHC class II DRB gene variability in wild and captive Bengal tigers (Panthera tigris tigris). Immunogenetics. 2011;63((2)):121. [PubMed: 20821315]
• Powell R.A. Animal home ranges and territories and home range estimators. In: Boitani L, Fuller T.K, editors. In Research Technologies in Animal Ecology: Controversies and Consequences. Columbia University Press; New York: 2000. pp. 65–110.
• Pusey A, Packer C. Once and future kings. Nat. Hist. 1983 August:55–62.
• Rabinowitz A.R, Nottingham B.G. Ecology and behavior of the jaguar (Panthera onca) in Belize, Central America. J. Zool. Lond. 1986;210:149–159.
• Rasmussen L.E.L. Evolution of chemical signals in the Asian elephant, Elephas maximus: Behavioural and ecological influences. J. Biosci. 1999;24((2)):241–251.
• Rishi V. The role of scent marking in the breeding behavior of tiger and other big cats. The Indian Forester. 2012;138((10)):910–914.
• Röck F, Hadeler K.-P, Rammensee H.-G, Overath P. Quantitative analysis of mouse urine volatiles: In search of MHC-dependent differences. PLoS ONE. 2007;2((5)):e429. [PMC free article: PMC1855987] [PubMed: 17487279]
• Russell K.P. Mountain lion. In: Schmidt T.L, Gilbert D.L, editors. In Big Game of North America. Stackpole Books; Harrisburg, PA: 1978. p. 494.
• Rutherfurd S.M, Zhang F, Harding D.R, Woolhouse A.D, Hendriks W.H. Use of capillary (zone) electrophoresis for determining felinine and its application to investigate the stability of felinine. Amino Acids. 2004;27((1)):49–55. [PubMed: 15309571]
• Sankar K, Qamar Q, Nigam P, Malik P.K, Sinha P.R, Mehrotra R.N, Gopal R, Bhattacharjee S, Mondal K, Gupta S. Monitoring of reintroduced tigers in Sariska Tiger Reserve, Western India: Preliminary findings on home range, prey selection and food habits. Trop. Conserv. Sci. 2010;3:301–318.
• Sankhala K.S. Tiger. Collins; London: 1978.
• Sankhala K.S. Tiger. Lustre; New Delhi: 1993.
• Schaller G. The Deer and the Tiger. University of Chicago Press; Chicago, IL: 1967.
• Schaller G. The Serengeti Lion. University of Chicago Press; Chicago, IL: 1972.
• Schieberle P. Quantitation of important roast smelling odourants in popcorn by stable-isotope dilution assays and model studies on flavor formation during popping. J. Agric. Food Chem. 1995;50:2442–2448.
• Schilling A. Organe de Jacobson du Lemurien Malagache. Memoire du Museum National d’Histoire Naturelle, Serie A. Zoologie. 1970;61:206–280.
• Singer A.G, Macrides F, Clancy A.N, Agosta W.C. Purification and analysis of a proteinaceous aphrodisiac pheromone from hamster vaginal discharge. J. Biol. Chem. 1986;261:13323–13326. [PubMed: 3759967]
• Singer A.G, Beauchamp G.K, Yamazaki K. Volatile signals of the major histocompatibility complex in male mouse urine. Proc. Natl. Acad. Sci. U. S. A. 1997;94:2210–2214. [PMC free article: PMC20066] [PubMed: 9122173]
• Singh A. Tara, a Tigress. Quartet; London: 1981.
• Sitton L.W, Wallen S. Calif. Department of Fish and Game; Sacramento, CA: 1976. California mountain lion study.
• Smith J.L.D, McDougal C.W, Sunquist M.R. Female land tenure system in tigers. In: Tilson R.L, Seal U.S, editors. In Tigers of the World: The Biology, Biopolitics, Management, and Conservation of an Endangered Species. Noyes Publications; Park Ridge, NJ: 1987.
• Smith J.L.D, McDougal C, Miquelle D. Scent marking in free-ranging tigers. Panthera tigris. Anim. Behav. 1989;37((1)):1–10.
• Smith R.M. Movement patterns and feeding behavior of the leopard in the Rhodes Matopos National Park, Rhodesia. Carnivore. 1978;1((3)):58–69.
• Soso S.B, Poddar-Sarkar M, Koziel J, Brahmachary R.L. More on “Aroma of tiger and…rice,” (abstract), 36th Annual Conference of Ethological Society of India and National Symposium on “Live organisms and their expression in the environment,” 2012. November 26–28, 2012, Kolkata, p. India 54.
• Spencer S.R, Cameron G.N, Swihart R.K. Operationally defining home range: Temporal dependence exhibited by Hispid cotton rats. Ecology. 1990;71((5)):1817–1822.
• Stander P.E, Haden P.J, Kaqece I.I, Ghau I.I. The ecology of asociality in Namibian leopards. J. Zool. Lond. 1997;242:343–364.
• Strauss B.S. An Outline of Chemical Genetics. Saunders W.B, editor. Philadelphia, PA: 1960.
• Thapar V. Tiger, the Portrait of a Predator. Collins; London: 1986.
• Thapar V. Tiger: The Ultimate Guide. Oxford University Press; New Delhi: 2006.
• Thavathiru E, Jana N.R, De P.K. Abundant secretory lipocalins displaying male and lactation-specific expression in adult hamster submandibular gland, cDNA cloning and sex hormone-regulated repression. Eur. J. Biochem. 1999;266:467–76. [PubMed: 10561587]
• Tinbergen N. The Study of Instinct. Oxford University Press; New York: 1951.
• Turnbull-Kemp P. The Leopard. Howard Timmins; London: 1967.
• Van den Hurk R. Pheromone Information Centre; Brugakker, Zeist, Netherlands: 2007. Intraspecific chemical communication in vertebrates.
• Van Der Merwe N.J. The Jackal. Fauna and Flora of Transvaal. South Africa: 1953. Prov. Admin., Publication No. 4.
• VanderWaal K.L, Mosser A, Packer C. Optimal group size, dispersal decisions and postdispersal relationships in female African lions. Anim. Behav. 2009;77:949–954.
• Verberne G. Beobachtungen und Versuche über das flehmen Katzenartiger Raubtiere. Z. f. Tierpsychol. 1970;27:807–827. [PubMed: 5511687]
• Vincent F, Lobel D, Brown K, Spinelli S, Grote P, Breer H, Cambillau C, Tegoni M. Crystal structure of aphrodiscin, a sex pheromone from female hamster. J. Mol. Biol. 2001;305:459–469. [PubMed: 11152604]
• von Uexküll J. A stroll through the world of animals and men. In: Schiller C.H, editor. In Instinctive Behavior: The Development of a Modern Concept. International Universities Press; New York: 1934.
• Voznessenskaya V.V, Parfyonova V.M, Zinkevich E.P. Individual odor types. In: Doty R.L, Müller-Schwarze D, editors. In Chemical Signals in Vertebrates 6. Plenum Press; New York: 1992. pp. 503–508.
• Wasser S.K, Smith H, Madden L, Marks N, Vynne C. Scent-matching dogs determine number of unique individuals from scat. J. Wildl. Manage. 2009;73:1233–1240.
• Westall R.G. The amino acids and other ampholytes of urine. 2. The isolation of a new sulphur-containing amino acid from cat urine. Biochem. J. 1953;55:244–248. [PMC free article: PMC1269227] [PubMed: 13093671]
• Wyatt T.D. Pheromones and Animal Behaviour: Communication by Smell and Taste. Cambridge University Press; Cambridge: 2003.
• Yamazaki K, Beauchamp G.K, Curran M, Bard J, Boyse E.A. Parent-progeny recognition as a function of MHC odor type identity. Proc. Natl. Acad. Sci. U. S.A. 2000;97:10500–10502. [PMC free article: PMC27053] [PubMed: 10973487]
• Yoshihashi T, Hung N.T.T, Inatomi H. Precursors of 2AP, a potent flavor compound of an aromatic rice variety. J. Agri. Food Chem. 2002;50:2001–2004. [PubMed: 11902947]

Footnotes

*

The male African elephant also utilizes the temporal pheromone as studied by Rasmussen and others. The African females and, more rarely, the Indian she elephants are known to secrete a watery (less viscous) fluid from the temporal gland, which is a sign of agitation rather than of pheromonal function.

*

International Tiger Stud Book published by Zoologischen Garten Leipzing, December 15, 1990 (Prof. Dr. rer.nat Siegfried Seifert, stud book keeper).

*

Not registered in the stud book.

†

Not registered in the stud book.