Elephants
Research in my lab on elephants has covered a wide spectrum of subjects including evolutionary ecology, foraging ecology, elephant-human interactions, poaching and population dynamics, social behaviour, reproductive physiology, stress physiology, vocal communication, genetics, conservation landscapes and cultural ecology. Some of this work is briefly described in this page and can be accessed through the published books, papers and reports.
Elephant-human interactions: My early work on the ecology of elephant-human interactions showed the strong influence of intrinsic biological factors such as nutritional needs and risk-taking behaviour of males in polygynous societies in crop raiding. Over the decades this theme of the human dimensions of wildlife continues to be a strong focus with students, postdocs and associates unraveling different facets of elephant social organization, physiology and habitat factors. Nishant Srinivasaiah has followed the emergence of large all-male elephant groups when these move into human-dominated landscapes primarily for crop raiding. Sanjeeta Sharma Pokharel has shown that crop raiding elephants outside of protected areas are in better body condition than elephants inside protected areas in southern India. Our research has also included trials mitigation tools including low cost chili-tobacco fence and the use of GPS telemetry as an aid in early warning of impending conflicts
Foraging ecology and the elephant's role in tropical forests: I pioneered the use of stable carbon isotopes to show that browse (C3 plants or the majority of trees and shrubs) contributed more protein than did grasses (C4 plants or tropical grasses) to elephant nutrition. Nitin Sekar used a combination of observational, experimental and modeling movement to show that elephants are by far the most important dispersers of fruits of many tree species in tropical forests.
Ivory poaching and population dynamics: I probably made the earliest estimates of selective poaching of male Asian elephants for ivory in southern India, and developed models of population dynamics under different intensities of poaching. These provided the basis for further model development in estimating the true extent of unnatural elephant death from population structures and sex ratios in present-day elephant populations.
Male dimorphism and sexual selection: Milind Watve's study on tusk length and intestinal parasite loads in male Asian elephants showed a negative relationship, thereby hinting that the primary function of tusks was signaling fitness (superior resistance to parasites and diseases) to attract females. Karpagam Chelliah's behavioural studies demonstrated that the expression of musth overrides the possession of tusks in male dominance over other males and attracting females for mating. Thus, tuskless males may neutralize any disadvantages in lack of tusks through enhanced expression of musth.
Genetics, evolution and diversity of Asian elephants:
TNC Vidya's work on mitochondrial and microsatellite DNA revealed a complex history of evolution and dispersal of elephants driven by the climatic oscillations (glacial cycles) of the Pleistocene. My recent collaboration with Anubhab Khan and Uma Ramakrishnan in using whole genomic sequences demonstrated that genetic variation declined along a north-south gradient as subsets of elephants which evolved in the north serially colonized habitats in the south of the Indian subcontinent. This has significant management implications.
Vocal communication in elephants: Elephants are known to communicate through low frequency or infrasound as well as high frequency calls. Smita Nair made one of the first attempts to document and characterize the sound spectrum of various calls and their possible contexts of Asian elephants. Nachiketa Sharma has since followed up with detailed documentation of Asian elephant call types and their behavioural contexts.
Reproductive and stress physiology of elephants: Polani Seshagiri and I have collaborated in developing and using non-invasive methods of monitoring estrous cycles in female elephants, measuring testosterone levels in male elephants, and in monitoring stress levels in elephants. Ratna Ghosal has carried out the assays of reproductive hormones while Sanjeeta Sharma Pokharel has been measuring glucocorticoid metabolites extracted from elephant dung. Interestingly, glucocorticoid levels were lower in crop raiding elephants in line with their better body condition in a southern Indian population.
Elephant telemetry for conservation planning: A large team of researchers and veterinarians has over the decades been pivotal in tracking, darting, sedating and fixing radio- and GPS collars on elephants in the states of West Bengal and Assam (northeastern Indian population) to understanding their movement ecology, home ranges, crop raiding patterns, and use of corridors in large landscapes
Evolutionary ecology of elephants: Rajeev Patnaik (Panjab University) and I have collaborated in using stable isotopes in tracing dietary shifts in ancestral elephant forms over the past 14 million years in the Indian subcontinent. While the overall shift from a browsing diet (C3 plants) to a grazing diet (C4 plants) in response to climate and vegetation change is not necessarily surprising, the dietary flexibility of the modern Asian elephant in historical times has provided some clues to their penchant for raiding cultivated crops.
