An animal’s ability to find thermal comfort can be can be limited within a zoo enclosure. This creates a need to design comfortable microclimates for the animal within their enclosure space. This is an exploratory study intended to investigate the relationships between an elephant’s movements throughout their space and the microclimatic conditions within its zoological enclosure. By outlining an understanding of microclimates and how they are affected by the landscape combined with knowledge of elephant behaviours it will be possible design or plan for microclimatic use within zoo enclosures. Observational data were collected from five Asian elephants (Elephas maximus). The movements of the elephants were monitored along with the use of microclimates within their enclosure. Thermal regulatory movements involving microclimatic use typically involved water and shade use, however evidence suggests that the animals were also avoiding terrestrial radiation from some of the gunite walls. It is important that animals are given the opportunity to find microclimates within the space to regulate their body temperature. Designing landscapes that incorporate microclimates within their habitats is crucial to the welfare and health of zoo elephants.

Behavioral evidence suggests that Asian elephants strongly rely on their sense of smell in a variety of contexts including foraging and social communication. Using a food-rewarded two-alternative operant conditioning procedure, three female Asian elephants were tested on their olfactory discrimination ability with 1-aliphatic alcohols, n-aldehydes, 2-ketones, n-carboxylic acids and with a set of twelve enantiomeric odor pairs. When presented with pairs of structurally related aliphatic odorants, the discrimination performance of the elephants increased with decreasing structural similarity of the odorants. Nevertheless, the animals successfully discriminated between all aliphatic odorants even when these only differed by one carbon atom. The elephants were also able to discriminate between all twelve enantiomeric odor pairs tested. Additionally, the elephants showed an excellent long-term odor memory and remembered the reward value of previously learned odor pairs after three weeks and one year of recess. Compared to other species tested previously on the same sets of odorants, the Asian elephants performed at least as good as mice and clearly better than human subjects, South African fur seals, squirrel monkeys, pigtail macaques, and honeybees. Taken together, these results support the notion that the sense of smell may play an important role in regulating the behavior of Asian elephants.

Depuis des millénaires, l’éléphant d’Asie joue un rôle important dans la culture, l’économie et la construction des pays asiatiques. Près d’un quart de la population de cette espèce emblématique et menacée est constituée d’éléphants dits captifs. Toutefois, les législations nationales comme les programmes de conservation ont tendance à traiter séparément les populations captives et sauvages. Au Laos et au Myanmar, la tradition d’élevage par les villageois et les interactions entre éléphants sauvages et éléphants de villages perdurent.L’objectif de cette thèse est de qualifier et quantifier ces interactions afin de mieux comprendre leurs dynamiques et leurs rôles dans la survie de l’espèce. Je me suis attaché à décrire les facteurs déterminant le système socio-écologique humain - éléphant de village - éléphant sauvage et sa résilience à travers une approche interdisciplinaire et intégrative.Une étude ethnoécologique a permis d’analyser l’évolution récente du système socio-écologique homme-éléphant au Laos et ses conséquences sur les relations humain-éléphant, les pratiques d’élevage et la perception de l’espèce chez les propriétaires d’éléphants. L'émergence depuis les années 2000 de la marchandisation de la nature et de la restriction de l'accès aux forêts a conduit, d’une part, à la ségrégation entre éléphants sauvages et éléphants de villages, et d’autre part, à l’intensification de l'élevage de ces derniers. Or, la tolérance des communautés à la présence des éléphants sauvages semble liée au principe de réciprocité. Ainsi, les propriétaires ayant accès aux mâles sauvages pour féconder leurs femelles acceptent leur présence contrairement aux cornacs engagés dans le débardage du bois.J’ai ensuite construit un modèle bio-économique pour quantifier les effets des stratégies socio-économiques sur la viabilité à long terme de la population d’éléphants de villages du Laos. J’ai montré que la fécondité est impactée en premier lieu par la dynamique de la population sauvage à travers la reproduction entre femelles de villages et mâles sauvages. En second lieu, le taux de fécondité dépend de l’intérêt financier des propriétaires à faire de la reproduction. Ainsi la viabilité de la population est fortement dépendante des conditions socio-économiques sur le court terme et de l’efficience de la conservation des populations sauvages sur le long terme.Une étude de génétique des populations a montré que la diversité génétique des populations sauvages et de villages était élevée et que ces populations constituaient un ensemble homogène au Laos et au Myanmar. L’isolement des populations sauvages et la ségrégation croissante des populations de villages engendreront un appauvrissement génétique sur le long terme qu’il est possible de limiter par des mesures de gestion favorisant le flux de gènes au niveau régional et entre les deux populations, notamment en les considérant comme une unité de gestion commune.Ces deux études illustrent que la résilience du système socio-écologique est la résultante de multiples facteurs agissant à différents niveaux ou échelles, dont les effets sont parfois opposés.Cette thèse permet enfin de discuter des conditions de la résilience et de la viabilité à long terme du système socio-écologique humain-éléphant et d’explorer différents scénarios futurs en s’interrogeant également sur le possible processus de domestication de l’espèce. / For thousands of years, the Asian elephant has played an important role in the culture, economy and construction of Asian nations. Almost a quarter of the population of this emblematic and threatened species consists of so-called captive elephants. However, both national legislation and conservation programmes tend to treat captive and wild populations separately. In Laos and Myanmar, the tradition of elephant handling by villagers and the interactions between wild and village elephants still persist.The objective of this thesis is to qualify and quantify these interactions to better understand their dynamics and roles in the survival of the species. I described the factors driving the socio-ecological system between humans, village and wild elephants and its resilience through an interdisciplinary and integrative approach.Based on an ethnoecological study, I analyzed the recent evolution of the human-elephant socio-ecological system in Laos and its consequences on human-elephant relations, husbandry practices and the perception of the species among elephant owners. The emergence since 2000 of the commodification of nature and the restriction of access to forests has led, on the one hand, to the segregation between wild and village elephants and, on the other hand, to the transition from a traditional to an intensive keeping system of village elephants. Community perception and tolerance towards wild elephants is linked to the principle of reciprocity. Owners having access to wild males to sire their females accept the presence of wild elephants contrary to mahouts engaged in logging activities.I then built a bio-economic model to quantify the effects of socio-economic strategies on the long-term viability of village elephant population in Laos. I demonstrated that fecundity is impacted primarily by the dynamics of the wild population through reproduction between village females and wild males. Second, the fecundity is impacted by the financial incentive of elephant owners tobreed their animals instead of working. Thus population viability is highly dependent on socio-economic conditions in the short term and the efficiency of wild elephant conservation in the long term.A population genetics study showed that the genetic diversity of wild and village elephant was high and differentiation was weak between Laos and Myanmar. The isolation of wild populations and the increasing segregation of village elephants will lead to genetic loss and inbreeding that can be managed by promoting gene flows at the regional level and between the two populations. The study suggests considering both populations from the two countries as a unique management unit. These two studies illustrate that resilience of the socio-ecological system is the result of multiple factors acting at different levels or scales, sometimes in opposite ways.Finally, this thesis allows to discuss the conditions of resilience and long-term viability of the human-elephant socio-ecological system and to explore potential scenarios including the on-going domestication process of the species.

No description available.

The sense of smell plays an important role in regulating the behavior of Asian elephants but until now, no behavioral test to systematically assess the olfactory capabilities of this species existed. Using a voluntary, food-rewarded two-alternative operant conditioning procedure, three female Asian elephants were successfully taught to discriminate between rewarded and unrewarded odors and also succeeded in intramodal stimulus transfer tasks in which either the rewarded odor, or the unrewarded odor, or both odors were exchanged simultaneously for new odors. The animals readily mastered the initial task within only 120 stimulus contacts, demonstrating rapid olfactory learning and performing at least as good as rodents and dogs and even better than other species, including nonhuman primates, tested in similar studies before. When presented with pairs of structurally related odorants, the discrimination performance of the elephants decreased with increasing structural similarity of the odorants, but the animals still significantly discriminated between aliphatic acetic esters even when they only differed by one carbon chain length. The elephants also demonstrated an excellent long-term odor memory and successfully remembered the reward value of previously learned odor stimuli after two, four, eight and even 16 weeks of recess in testing. The paradigm developed and applied in the present study proved to be useful to assess the olfactory capabilities in Asian elephants.

Compromised welfare and wellbeing of elephants (Loxodonta africana and Elephas maximus) in captive facilities are significant and global problems. The period between birth and two years old is crucial for calf survival and social and environmental learning. Behaviour and developmental processes among captive elephant calves in these first years were compared with those seen in wild calves. Wild elephants calves develop within a complex, varied social context and provide one reference for normal patterns of development. Such comparisons enable insights into welfare at captive facilities. Eleven captive elephant calves born at three UK facilities were studied from birth to 18 months (AsianN=6; AfricanN=5). Older calves (AsianN=2; AfricanN=2) were also sampled up to 3.5 years; making a total of 15 calves studied from 2009 to 2014. Due to the small sample size, the 11 younger calves were also discussed as individual case studies. By 2017, only two of these case study calves were both alive and not orphaned. Three additional calves (AsianN=1; AfricanN=2) died on their day of birth and were not sampled. This small sample highlights the ongoing lack of self-sustaining populations of captive elephants. This thesis collated systematic behavioural observations on captive calves across 373 days (483.5hrs). Calf maintenance activities (feeding, resting, moving), associations with mother and others, interactions and calf play were compared with behavioural observations of wild AsianN=101 (74hrs, Uda Walawe, Sri Lanka) and wild AfricanN=130 (252hrs, Amboseli, Kenya) calves from ~birth to five yrs. Mothers’ (captive: AsianN=4; AfricanN=4; wild: AsianN=90; AfricanN=105) activities were also recorded to explore synchrony with calves. Captive calves raised by their mothers had similar activity budgets to those seen in the wild. Expected age-related declines in suckling were found in captivity. However, captive calves were more independent than wild calves for their age in distance from mother and spent significantly more time in play. A Decision Tree for whether to breed elephants in captivity was developed; benefits that a calf potentially brings to companions, e.g. multi-generational matrilineal groups, enabling social bonding and reducing abnormal behaviours, were considered against space required for families to grow and divide naturally over time, as well as ensuring that captive-bred males are socially sustained. It was recommended that facilities invest in future enclosure/housing designs which permit: free-access to other elephants; 24hr trickle feeding; juvenile males allowed to stay with their maternal group for longer, encouraging learning opportunities and further retaining age-structure/composition. Conversely, facilities unwilling to house a male or provide appropriate group size/composition are recommended to cease breeding.

The Asian elephant (Elephas maximus), a charismatic ‘flagship species’, is threatened by extinction in the wild, and the development of self-sustainable captive populations is a key conservation challenge. A third of the Asian elephant population is presently in captivity and information on the reproductive status, especially in females, is still lacking to a large extent. The onset of estrus in female Asian elephants is not associated with any visible physical signs, thus making the assessment of the reproductive status rather difficult. One approach to understanding reproductive cyclicity of animals is through generating profiles of reproductive hormones in blood (Wiseman et al. 1983; Brown et al. 1999, 2004). Profiles of reproductive hormones such as progesterone (P4), estrogen, luteinizing hormone and follicle stimulating hormone have already being demonstrated in Asian elephants (Brown et al. 1999, 2004; Brown 2000). In these studies, the reproductive status of females, maintained in zoos/captivity, was characterized based on circulating levels of hormones in blood samples. This is difficult to implement in the case of semi-captive or wild populations of elephants due to practical, legal and ethical considerations. In order to overcome this problem and to better understand the estrous status of female elephants, it is important to develop and validate non-invasive methods to monitor the reproductive status of female Asian elephants. An alternative approach to evaluating the reproductive status of females is to consider behavioral responses shown by males towards chemical signals produced by females to advertise their reproductive status. In order to understand the reproductive status of the individual belonging to the opposite sex, studies have shown that elephants rely on a variety of chemical signals produced in biological fluids such as urine, temporal gland secretion, inter-digital gland secretion, etc. (Krishnan 1972; Rasmussen & Schulte 1998). Chemical signaling is one of the prominent modes of communication in elephants, especially with respect to locating potential mates (Sukumar 2003). Thus, in most cases, elephants usually employ specific behavioral responses, for example sniff, check and place behaviors of trunk, for investigating the reproductive status of the conspecific individual, belonging either to the same or the opposite sex (Rasmussen et al. 1996; Schulte & Rasmussen 1999; Bagley et al. 2006). The objectives of the thesis are two-fold. First, to develop a non-invasive method of reproductive monitoring from fecal hormonal metabolites and also to understand the possible role of feces as an inter-sexual signal. The main body of thesis is divided into four chapters. 1) Development and validation of a non-invasive method to estimate progesterone metabolite in feces, to monitor the reproductive cyclicity of female elephants (Chapter 2). 2)Generation and characterization of progesterone and its metabolite, 5α-P-3-OH, profiles of semi-captive females using the developed non-invasive method to measure fecal metabolites (Chapter 3). 3) Validation of developed methodology and assay systems to a wild-population of female elephants (Chapter 4). 4) Feces as a potential source for inter-sexual chemical signaling in Asian elephants (Chapter 5). The above studies were carried out on semi-captive male and female elephants maintained in the forest camps of Mudumalai Wildlife Sanctuary (MWLS), Tamil Nadu and Bandipur National Park (BNP), Karnataka, India (Chapters 2, 3 and 5). For Chapter-4, free-ranging females of the MWLS were examined. 1. Development and validation of a non-invasive method to estimate progesterone metabolite in feces, to monitor the reproductive cyclicity of female elephants Niemuller et al. (1993) generated a profile of the progesterone metabolite, 5βpregnanetriol, to assess the estrous phase of Asian elephants based on non-invasive urine sampling. However, the collection of urine is difficult and to some extent impossible in the case of semi-captive and as well as that of wild elephants. Thus, the method of choice in this study was the development and validation of a non-invasive approach to measure fecal progesterone metabolites to assess reproductive status of females. Sampling was carried out at monthly intervals on three female elephants at the MWLS forest camp, while three other females maintained at the BNP forest camp were sampled fortnightly. An enzyme linked immuno-sorbent assay was developed to measure the concentration of the progesterone metabolite, 5α-P-3OH in the fecal samples of the semi-captive females. Using varying concentrations of the hapten (5α-P3OH), from low (0.1 mM) to high (1 mM), a standard curve was first generated, which had a linear range between 0.25 mM to 62.5 mM, with an EC50 of 1.37 mM. The linear range was then used to detect the concentrations of 5α-P-3OH in the fecal samples of females examined. The non-invasive method was further validated as there existed a positive correlation (p<0.1) between the levels of fecal 5α-P-3OH and that of concentration of circulating P4, measured in blood samples. This is the first valid documentation of a non-invasive method based on fecal progesterone metabolite pattern in order to assess the reproductive status of the female Asian elephants. 2. Generation and characterization of reproductive hormone profiles of semi-captive females using the developed non-invasive method to measure fecal metabolites With the establishment of a non-invasive method to understand occurrence of estrus in female elephants (described in Chapter 2), attempts were made to generate hormonal profiles over a longer time interval through more frequent sampling. Based on sampling at weekly intervals, the concentrations of both fecal 5α-P-3OH and that of native P4 hormone in the blood were determined, and the females were then identified as belonging to different reproductive states of hormonal cycling (follicular and luteal phases), non-cycling and pregnant categories. Of the 7 females sampled at both MWLS and BNP, three distinct categories of hormone-metabolite profiles emerged. The first category included four females that showed regular cyclicity throughout the sampling period, as monitored through the measurement of fecal 5α-P-3OH and serum P4 levels. The estrous cycle of all the four females was divided into two phases (follicular and luteal), based on the patterns of fecal 5α-P-3OH and serum P4 concentrations. The follicular phase of the estrous cycle was assigned when the values of both fecal 5α-P-3OH and serum P4 remained below 0.3 µg/gm and 0.3 ng/ml, respectively, for a considerable time period (viz. >2 wk). However, the luteal phase was characterized, when the levels of fecal 5α-P-3OH and serum P4 remained at or above 0.3 µg/gm and 0.3 ng/ml respectively, over a period of more than 2 - 3 wk. The second category had two females showing a ‘flat-lining pattern’ for the levels of fecal 5α-P-3OH and serum P4 concentrations, without any peak or dip in their concentrations. Since the reproductive pattern for both these females was flat-lined throughout their sampling period (51 wk), maintaining the levels of fecal 5α-P-3OH and serum P4 below 0.3 µg/gm and 0.3 ng/ml respectively, the females were considered to be non-cycling or anestrus. The third category had one female in which the levels of both fecal 5α-P-3OH and serum P4 measured were consistently high throughout the entire sampling period (26 wk). The levels of both fecal -P-3OH and serum P4 were above 0.3 µg/gm and 0.3 ng/ml, respectively. At the end of the sampling period, this female delivered a male calf; thus, the measured concentrations of fecal 5α-P-3OH and serum P4 signified the levels maintained during the gestational phase of this female. Sampling and hormonal analyses were also carried out for a male in the MWLS forest camps to investigate the baseline concentrations of fecal 5α-P-3OH and serum P4. The male showed consistently low concentrations of both fecal 5α-P-3OH and serum P4 throughout the sampling period (16 wk), below the margin of 0.3 µg/gm and 0.3 ng/ml, respectively. In this part of the study, it was confirmed that the reproductive status of a female elephant can be correctly assessed on the basis of measurements of fecal 5α-P-3OH alone, with repeated sampling of the female over a longer time scale. It was also shown that the strength of the positive correlation between the concentrations of the fecal 5α-P3OH and the serum P4 increased (p<0.01) for a larger sample size than that obtained for a comparatively smaller sample (described in Chapter 2). 3. Validation of developed methodology and assay systems to wild-population of female elephants So far, the non-invasive method to estimate fecal progesterone metabolite in order to predict occurrence of estrus of elephants was largely applied to semi-captive females (described in Chapters 2, 3). However, the necessity of such a method is being recognized for assessing the reproductive status of free-ranging females. Several findings have described differences in the rate and type of steroid metabolite excretion among individuals maintained under different diet regimes (Wasser et al. 1993; Smith et al. 2006). For instance, female elephants in the forest camps are provided with supplementary diet consisting of sugarcane, rice and millets. This diet is strikingly different from the feeding materials consumed by wild/free-ranging elephants (Sukumar 2003). Therefore, differences in dietary components can potentially influence the fecal steroid metabolites’ excretory patterns shown by semi-captive vis-a-vis wild females, which can affect the validity of measuring fecal 5α-P-3OH to predict females’ reproductive status. In order to examine this problem, the non-invasive method was applied to the population of wild elephants in the forests of MWLS, through random one time sampling of 30 individual female elephants. The steroid extraction efficiency (73 ± 11.0%, mean ± S.D., n =30) determined for the fecal samples collected from the wild females was not significantly different from the coefficient calculated in the case of the semi-captive females (80 ± 4.3%, mean ± S.D., n = 38). This indicated that dietary differences between wild and captive elephants did not influence levels of fecal hormonal metabolites in feces, unlike earlier observations on baboons (Wasser et al. 1993), old world primates (Wasser et al. 1988) and sheep (Smith et al. 2006). The values of the fecal allopregnanolone determined in the case of the wild females, ranged from as low as 0.06 µg/gm to as high as 23µg/gm of the sample, thus showing the heterogeneity of the samples, indicating that the females may be belonging to different reproductive phases. However, since sampling was carried out randomly, with an adult female being sampled just once, at this stage, it is not possible to identify or elaborate on the reproductive phase of the females. This is the first study reporting the values of the fecal progesterone metabolite in female Asian elephants in the wild. Further studies may be required to carry out long term monitoring of the wild females, through repeated collection of fecal samples over time from particular female. 4. Feces as a potential source for inter-sexual chemical signaling in Asian elephants In this Chapter-5, behavioral trials were conducted on male elephants to understand the role of fecal matter in conveying inter-sexual chemical signals. This was demonstrated by analyses of specific chemosensory behavioral responses shown by males towards the fecal samples of females that were strangers and belonging to different reproductive stages. Males showed four prominent behavioral responses namely ‘distant sniff’, ‘close sniff’, ‘check’ and ‘place’ towards the fecal samples of females. The sum of frequencies of these four responses (distant sniff, close sniff, check and place) was much higher for samples of the follicular (pre-ovulatory) phase females as compared to those of the luteal (post-ovulatory) phase females (p<0.005). Thus, for the first time, it was shown that male elephants are able to discriminate the different reproductive phases of females based on their specific behavioral response towards the fecal samples of the opposite sex. In conclusion, the thesis has focused on understanding and providing new insights regarding the reproductive biology of the female Asian elephants. This has been achieved through the development of the non-invasive method based on measuring the concentrations of the fecal progesterone metabolite and through the analyses of the chemosensory responses performed by the males towards the fecal samples of strange females. These methods can potentially be applied to the populations of both wild and captive/semi-captive female elephants in order to evaluate their reproductive status, through non-invasive measures. The information derived from the application of such methods will help in understanding the reproductive potential of the wild elephants under various environmental and ecological conditions. Further, the non-invasive measurement of reproductive hormones will help in monitoring the reproductive state of the individuals and thus aid in planning strategies for the welfare and management of the elephants maintained in captive or semi-captive conditions.

Darwin was troubled by elaborate male traits observed in many species that are seemingly maladaptive for survival, the peacock’s tail being the most iconic of all. He wrote "The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick" because it challenged his theory of evolution by natural selection for adaptive traits. The extreme length of the tail may render a peacock more vulnerable to predation and therefore maladaptive for survival. To account for the evolution of apparently maladaptive traits he proposed the theory of sexual selection, wherein, traits that directly enhance mating success may be selected for, either as weapons in male-male competition for mates or as ornaments preferred by females. Male and female elephants in the proboscidean evolutionary radiation have had tusks and show extreme exaggeration in size and form. However, tusk in the Asian elephant (Elephas maximus) is sexually dimorphic as it is expressed only in the males, hinting at a possibility that opposing selection (sexual selection advantage to males and natural selection disadvantage to females) may have been the processes behind this pattern of tusk expression. Intriguingly, tuskless males (male dimorphism with respect to tusk) also occur at fairly high frequencies in some Asian elephant populations (∼50% in norteastern India and ∼95% in Sri Lanka). Theory states that dimorphic males can also occur in a population in stable frequencies as a consequence of sexual selection. I explored sexual selection on elephant tusks as possible mechanism leading to the observed patterns of tusk dimorphism in the elephants. All elephant populations on earth have been harvested for ivory, therefore, artificial selection (selective poaching of tusked elephants for ivory) is another possible cause of tusk dimorphism. I developed mathematical models of population genetics, population dynamics and conducted field observations of mating behavior of Asian elephant in Kaziranga National Park, Assam to understand the evolution of tusk dimorphism in elephants. Darwin’s sexual selection theory was controversial when proposed in 1871 and continues to remain so in 2014. In the introduction of my thesis I have discussed Darwin’s two classical mechanisms of sexual selection, namely, male-male combats for mates and female mate choice based on male traits. The latter was viewed with considerable skepticism by his con-temporary Alfred Russell Wallace and more recently deemed "fundamentally flawed" by Joan Roughgarden. Therefore, I have also discussed the arguments against female mate choice for male traits found in literature. I have reviewed current knowledge about sexual selection for sexually dimorphic male traits of body size and musth, in the African and Asian elephant and state why I have hypothesized that tusks may also be under sexual selection. Sexually selected traits are expected to be genetically determined, therefore, I explored mathematically (Chapter 1) the genetic basis of evolution of sexual dimorphism. Fisher proposed that sexually selected male display traits originate in both the sexes but are suppressed in the females by modifier genes, when the trait becomes deleterious to females. Thus, sexually antagonistic selection on a trait and sex-specific gene expression can lead to the evolution of sexual dimorphism. Tusk is sexually monomorphic in the probocideans that are ancestral to both the African (Loxodonta africana) and Asian elephant (Elephas maximus). Tusk continues to remain monomorphic in the African elephant but has become sexually dimorphic in the Asian elephant. Tusk, therefore could be a sexually selected male trait that evolved according to the Fisherian model. Intriguingly, tuskless males occur at very high frequencies in some Asian elephant populations. The tusked and tuskless male morphs could be alternate male mating strategies, occurring at evolutionarily stable frequencies. Alternatively, the observed male tusk dimorphism, could be a consequence of artificial selection against tusked individuals, due to selective harvest of tusked males. Furthermore, male African elephants are more intensely poached for ivory than female elephants. Yet the frequency of tuskless individuals has increased more rapidly among females than in males. In essence, sexual dimorphism could be evolving among such poached populations. Is such rapid, contemporary evolution of sexual dimorphism, possible through the Fisherian modifier gene mechanism? A 2-loci genetic model (with X-linked trait gene and an autosomal modifier gene) (Rice 1984), a slight variant of the model (with X-linked modifier gene, and an autosomal trait gene) and an entirely autosomal model, were analyzed for the rate of evolution of sexual dimorphism, under different selection pressures for tusk possession. Negative frequency dependent selection was introduced into the model of tusk evolution in accordance with Gadgil’s model for the evolution of male dimorphism as consequence of sexual selection (Gadgil 1972). In two of the 2-loci models (in which tusk gene in autosomal), tusklessness evolved much more rapidly in females than in males, under equal negative selection pressures. The models predict several combinations of time-lines and negative selection pressures for effecting a particular change in the frequency of tusklessness. Model predictions were com-pared with observed changes in the frequency of female tusklessness, in one South Ugandan, African elephant population (∼2% to 10% in 5 to 9 generations) and male tusklessness (∼5% to 50% in 25 to 40 generations) in one north eastern Indian, Asian elephant population. The models predict strong selection pressures of 30% to 50% reduction in fitness, that can effect an 8% increase in tusklessness, in the African elephant population, within time-lines of 9 to 5 generations (∼225 to 125 years) respectively. For the male Asian elephants, natural selection against tusked males on an already sexually dimorphic population, must have been in operation and shifted the population to 5% male tusklessness. The models predict that artificial selection with 20 to 30% fitness cost to tusked males, operating for 40 to 25 generations (∼1000 to 600 years) respectively, can further shift the population from ∼5% to ∼50% tusklessness. Asian elephant populations may already have been in a transient phase of evolution, tending towards tusklessness, with recent artificial selection hastening the process. The two major pre-dictions from this modeling exercise are (1) artificial selection could have played a significant role in the evolution of male tusk dimorphism in the Asian elephant (2) a lack of or very mild current sexual selection on tusks in the male Asian elephant. Both these predictions may be empirically verified. Chapters 2 and 3 are attempts at empirical verification of prediction (1) and Chapters 4 and 5 of prediction (2). From historical references to elephant harvest in Assam, we do know that artificial selection has been in operation, but whether it has played a major role in causing male tusk dimorphism needs to be established. It may be possible to detect signatures of significant past harvest from current demographic structure of an elephant population. Sustained biased harvesting of a particular sex and or age class from an animal population alters the sex ratio and age structure (relative proportion of individuals in each age and sex class) of a population considerably (Sukumar 1989). It may be possible to back infer the harvest scenario by studying the deviation of current age and sex ratios from natural age and sex ratios. In Chapter 2, I explored models of population dynamics under different harvest regimes and its effect on age and sex ratios. I described a method to infer unknown harvest rates and numbers from age and sex ratios, namely, adult female to male ratio, male old-adult to young-adult ratio, and proportion of adult males in the population using Jensen’s(2000) 2-sex, density-dependent Leslie matrix model. The specific combination of male and female harvest rates and numbers can be deter-mined from the history of harvest and an estimate of population size. I validated this model with published data on age and sex ratios of one Asian and African elephant population with fairly reliable data on elephant harvest as well. In Chapter 3, I applied this model to the demographic data that I collected from a wild Asian elephant population in Kaziranga National Park, Assam, India (where more than 50% of the adult males are tuskless). Male polymorphism of sexually-selected male traits occur at stable frequencies in populations of several species. The different male morphs of the trait are hypothesized to be alternate male mating strategies with equal life time reproductive fitness. Male Asian elephants of Kaziranga National Park, Assam are dimorphic with respect to tusk possession: ∼50% of the males are tuskless (and are locally called makhnas). Makhnas could be trading tusk for either longevity, larger body size, testicular volume and or duration of musth as alternate mating strategies. On the other hand makhnas may have increased to a very high frequency primarily due to selective removal (captures for domestication and hunting for ivory) of tusked males from the population for centuries. The aim of Chapter 3 was to examine the role of artificial selection in the evolution of makhnas. Prolonged male-biased harvest(removal from the population) is bound to alter the demographic structure of the population and leave a signature of the intensity and type of harvest on the residual population structure. The Kaziranga elephant population was considered as representative of elephant populations of north east India; A harvest modeling approach (described and validated in Chapter 2) was used to infer unknown harvest of elephants from demographic parameters estimated by sampling this elephant population during 458 field days in the dry season months of 2008–2011. The Kaziranga elephant population appears to have been harvested approximately for the past 700 to 1000 years with adult tusked males being harvested at approximately twice the rate of adult tuskless males, adult females and their immature offspring of both the sexes. The currently observed high frequency of tuskless males in Kaziranga therefore, may be a consequence of sustained artificial selection against tusked males for several centuries. The previous two Chapters have only examined some mechanisms for the loss of tusks in elephants. I proceeded to examine the possibility of evolution of tusks through Darwin’s mechanisms of male-male competition for mates and female mate choice. Elephant tusks are cited as an example of a male trait that has evolved as a weapon in male-male combats. In Chapter 4 I examined the role of tusks in establishing dominance along with two other known male–male signals, namely, body size and musth (a temporary physiologically heightened sexual state) in an Asian elephant population in northeastern India with equal proportions of tusked and tuskless males. I observed 116 agonistic interactions with clear dominance outcomes between adult (>15 years) males during 458 field days in the dry season months of 2008–2011. A generalized linear mixed-effects model was used to predict the probability of winning as a function of body size, tusk possession and musth status relative to the opponent. A hierarchy of the three male–male signals emerged from this analysis, with musth overriding body size and body size overriding tusk possession. In this elephant population tusk possession thus played a relatively minor role in male–male competition. An important implication of musth and body size being stronger determinants of dominance than tusk possession is that it could facilitate rapid evolution of tuskless males in the population under artificial selection against tusked individuals, which are poached for ivory. If not a weapon, tusks could be a male ornament that female elephants find attractive. I explored the interplay of the three male traits (body size, musth and tusk), male mating strategies and female mate choice in Chapter 5. In some species males obtain mating opportunities by harassment of females. Given the striking size difference between an adult male and female elephant, with males weighing at least 30% more than females, male coercion of females to mate is a possibility. A detailed study of the courtship behavior revealed that overt male harassment of females is rare and the ability of a male to mount and stay mounted on a female for copulation is under female control. Therefore female Asian elephants can exercise choice to mate but this is subtly different from exercising mate choice itself. Age-related male mating strategy (reported for the first time in the Asian elephant) exists in the Kaziranga elephant population and this strategy limits the ability of females to exercise choice. Young males (<25 years) predominantly show a sneak mating strategy. Middle-aged males (25–40 years), when in musth, mate–guarded oestrous females from sneakers and attempted mating but sometimes resorted to sneak mating when out of musth. Old males (> 40 years) attempted mating only during their musth phase and were seldom sneakers. Large/musth males received positive responses from estrous females towards courtship attempts significantly more often than did small/non–musth males. Tusked non–musth males attempted courtship significantly more often than did their tuskless peers, and had a higher probability of receiving positive responses than did tuskless males. A positive response, however, may not translate into mating because of mate–guarding by the dominant male. Females permitted large/musth males to stay mounted significantly longer than small/non-musth males. Musth and large body size may be signals of male fertility. Female mate choice in elephants thus seems primarily for traits that signal direct benefits of assurance of conception. Tusked males may attain sexual maturity faster than tuskless males. Therefore it is worth exploring if tusks function as signals of male fertility when males are young (15 to 25 years); this may be possible through hormonal and behavioral profiling of young tusked and tuskless males from 10 to 20 years of age. Overall all musth and body size appear to play a larger role in enhancing male mating success than tusks. Tusked males appear to have a weak sexual selection advantage (male-male domi-nance and female preference) over their tuskless peers, only in the young age class (15 to 25 years) in this population. Males in this age age class, seldom come into musth that would over-ride tusk as a signal of male dominance. Current sexual selection on tusks in this population, appeared to be insignificant and this may be verified through genetic analysis of paternity success. An important implication of musth and body size being stronger determinants of mating success than tusk possession is that, it could facilitate rapid evolution of tuskless males in the population under artificial selection against tusked individuals, even in a slow breeder such as the elephant. Musth may have evolved much later than tusks in elephants, therefore it is possible that tusks evolved under sexual selection before musth evolved. However, body size, in mammals in gen-eral appear to be under both natural and sexual selection. Gould has shown that the absurdly large and palmate antlers of the extinct Irish elk, scales allometrically with body size (Gould & Lewontin 1979). Phylogenetic studies of elephant evolutionary radiation indicate a general trends towards increase in body-size with size reduction and tendency towards dwarfism occurring only in island habitats (Palombo 2001). Tusk development, which is essentially tooth development may be closely linked to cranium development. Cranium development in turn may be linked to body size through allometric scaling laws. If so, any selection on body size is bound to act on tusk size. I propose that the evolution of elaborate tusks seen in elephants is primarily due to natural and or sexual selection acting on body size, and tusk just hitched a ride with body size. Tusks may be maintained in spite of tuskless males occurring in the population only because of a rather weak sexual selection advantage to tusk possession in contests in which males are symmetrical with respect to body size and musth status.