Latest Events
Hummingbirds live fast. They have among the highest metabolic rates of all vertebrates, and must eat frequently to stay alive. I am excited to share with you some of the strategies they use to manage their time and their energy during the day. As a hummingbird, would you maximize energy gain or minimize energy loss, and how would your strategy change based on changing environmental conditions? And then, what do you do at night, when you do not have access to food? Hummingbirds save energy by entering the hibernation-like state of torpor. They manage to get very cold (~50°F/10°C) and slow their metabolism down. How do they do that and still stay alive? This is what I am currently working on finding out. Moving forward, for my independent research career, I plan to study comparative avian heterothermy on a global scale, starting by collecting data from the tropics while training biologists from the tropics. I plan to continue to integrate ecology, physiology, evolutionary perspectives, and molecular and imaging techniques to understand how heterothermic animals exist.
Sex-biased predation occurs when one sex of a prey species is consumed more than the other. Some of the potential factors leading to sex-biased predation are skewed natural sex-ratio and sex differences in morphology and/or behaviour of prey species. In the context of mate-finding, we often see sex-specific behavioural strategies, such as signalling and searching. The relative risk of predation on the two sexes during mate-finding depends on who signals, who searches, the risks associated with these behaviours, and the degree of involvement in these activities. Prey wing remains found in the roosts of a bat predator, Megaderma spasma, reveal interesting patterns for two katydid genera, Mecopoda and Onomarchus. Mecopoda sp. wing remains are male-biased in the breeding season and female-biased in the non-breeding season, while Onomarchus uninotatus wing remains are female-biased year-round. These two katydids differ in their mate-finding strategies: in Mecopoda sp., which are found close to the ground, males signal acoustically and females search silently to locate them. Onomarchus uninotatus is an arboreal katydid, that uses an acoustic-vibratory multimodal duet for mate-finding within trees, with both sexes signalling and searching to find mates.
To explore the factors driving the sex-biased predation by M. spasma on Mecopoda sp., we used a combination of field observations and enclosure experiments with wild-caught live animals. The males and females of Mecopoda sp. were compared with respect to (i) their availability, i.e., natural sex-ratio across the seasons, (ii) the predation risks associated with different behaviours, and (iii) the prevalence of their risky behaviours in the wild. We found that the relative availability of the sexes does not explain the male-biased predation on Mecopoda in the breeding season; whereas in the non-breeding season, very few males are available, which could lead to the female-biased predation. Males perform high-risk mate-finding behaviours, such as calling and flight, with a high prevalence in the wild. Although flight is equally risky for both sexes, females rarely fly.
To understand bat predation risk on male and female O. uninotatus and its possible role as a selection pressure driving the evolution of multimodal duetting, we performed outdoor enclosure experiments with live bats and katydids. Bat predation risks were compared (i) between the signalling and searching strategies of each sex, and (ii) between male and female signalling. We found that bat predation risk fails to explain the evolution of vibrational signalling in O. uninotatus females, as searching by walking is as safe as signalling, leading to an overall low predation risk on females within a tree. However, their duetting behaviour lowers the risk on males, who can shift from high-risk signalling to low-risk searching by walking, once females start signalling.
Finally, we focused on bat predation risk of searching behaviour in O. uninotatus, which potentially takes flights across trees. We compared (i) flight risks for O. uninotatus males and females in enclosure experiments and (ii) their across-tree movement pattern using radio-telemetry. We found that flight is equally risky for the sexes, but females move across trees 1.6 times more often and 1.8 times greater distances, which could make them more vulnerable to predation, explaining the female-biased prey remains found in M. spasma roosts.
Overall, this thesis provides a comprehensive examination of the predation risks associated with signalling and searching behaviours of katydids. The interplay between sex-specific behaviours and ecological factors, can explain sex-biased predation patterns.
Trait polymorphisms are widespread in nature, and explaining their stable co-existence is a central problem in ecology and evolution. Alternative reproductive tactics, in which individuals of one or more sex exhibit discrete, discontinuous traits in response to reproductive competition, represent a special case of trait polymorphism in which the traits are often complex, behavioral, and dynamic. Thus, studying how alternative reproductive tactics are maintained may provide general insights into how complex trait polymorphisms are maintained in populations. We construct a detailed individual-based model based on extensively collected empirical data to address the mechanisms behind the co-existence of three behavioural alternative reproductive tactics in males of a tree cricket (Oecanthus henryi). Our results show that the co-existence of these tactics over ecological time scales is facilitated by the spatial structure of the landscape they inhabit, which serves to equalize the otherwise unequal mating benefits of the three tactics. We also show that this co-existence is unlikely if spatial aspects of the system are not considered. Our findings highlight the importance of spatial dynamics in understanding ecological and evolutionary processes and underscores the power of integrative approaches that combine models with empirical data.
In December 2022 the 15th Conference of the Parties to the Convention on Biodiversity agreed a series of measures that requires ‘effective conservation and management’ of 30% of the world’s lands, waters and oceans. Determining where this attention should be directed – the exercise of conservation prioritisation – preoccupies many of the world’s leading conservation scientists. Conservation prioritisation is data hungry. It requires numerous data layers depicting land cover and land cover change, eco-region maps, agricultural activity, human populations, wealth, species distribution, predictions of how all these will change as the climate warms and so on. In this presentation I outline a new way of looking at the challenges of prioritisation by considering the data justice issues that it presents. I outline first why we need to think about data justice, and how it differs from other established concepts like epistemic justice. I then discuss what forms of data are being used in some conservation planning exercises and how using a data justice lens can help us better to understand the challenges they pose. I suggest practical ways of responding to some of the ethical challenges that arise.
Through the detailed unpacking of a colonial era fishing permit, known as the Boat License Certificate (BLC), operationalized in the Sundarbans National Park, this paper argues that some of the most exciting contributions of conservation work in India could be work that contends with the excruciatingly boring, bureaucratic, and pedantic work of paperwork. This would entail undoing an archaic set of fines, fishing licences and boat permits that have, over the years, generated a fearful regime that ‘incorporates illegality.’ BLCs not only convert the forest into a hostile environment, plunge Sundarbans fishers into new forms of inequality, but are also counterproductive to the goal of conserving the forest ecosystem. This ‘fishy’ business of fishing permits—closely interlinked to party politics and vote-bank politics—is something that all local, national, and international conservation organisations as well as the West Bengal Forest Department are aware of in the context of a global conservation hotspot. So why is it then that not a single conservation organisation is interested in tackling a regime of colonial licences that do not benefit the ecosystem or the fishing community? This paper suggests that conservation work in the Sundarbans, and in other national parks in India, is deeply depoliticized. In order for it to be genuinely transformative, it needs to contend with the boring work of paperwork.
Symposium highlighting work done at Prof. Rohini Balakrishnan's lab over the past 25 years.
Patterns of space use are key in understanding predator-prey interactions. The spatial overlap of predators with their prey influences their encounter rates, predation rates, and ultimately predator-prey dynamics. Animals engage in a dynamic behavioral response race, where prey actively try to avoid predators while predators seek out prey-rich spaces. Many extant studies fail to test for the emergent outcome of the dynamic space-use response race because they either fail to test for the dynamic responses of predator and prey when both are mobile or not addressing the underlying fine-scale behavioral mechanisms that drive space use in mobile predators and prey. In a qualitative literature survey, I examined how many studies report spatial and or temporal correlations between the distributions of mobile predator and prey and identified external constraints or ‘anchors’ that may influence the observed distributions. Anchors are defined as constraints like fixed resources or the presence of refuges that restrict free access to patches of choice. If only prey are constrained, predators can win the behavioral response race by achieving a positive spatial overlap with the prey, whereas a negative correlation may be seen if predators are constrained. Our results show that the presence of the identified anchors significantly influence the reported outcomes of the predator-prey space-use patterns. Such anchors can become important predictors of the emergent space-use patterns in predator-prey systems, making their identification vital in studies of predator-prey population dynamics and applied ecology. I then studied how predators from the African savanna choose home ranges based on the seasonal and yearly scales and how these timescales affect their choice of kill hotspots. I used movement data for tagged leopards and African wild dogs from the Karongwe Game Reserve in South Africa for this analysis. Our results show that the seasons affect where animals choose to hunt within their home range and that the choice of the home range itself may also change over seasons and years. There was also a difference in the space-use of leopards and wild dogs as expected from the differences in their behavioral mechanisms and hunting strategies. Overall, from movement data analysis, we conclude that a positive spatial overlap alone may not translate to uniform predation risk in the landscape as there are certain hotspots with higher encounters and predation activity that are riskier for prey. Future studies should focus on environmental constraints, intrinsic factors, and fine scale behavioral responses to explicate predation risk and ultimately its effect on predator-prey dynamics in a system.
Inclusive Ecology is an online workshop organised by the Centre for Ecological Sciences, Indian Institute of Science, Bengaluru.
The workshop will introduce participants to broad concepts and approaches in the fields of Ecology, Evolution, Behaviour, Conservation and Quantitative Thinking via workshops. We will also conduct workshops on building professional skills, careers in ecology, and life as a PhD. student.
The workshop is targeted to students from under-represented backgrounds, including those from rural areas and socioeconomic minorities.
Annual In-house symposium where members of CES speak about their research.
In this talk, Professor Oscar Horta will provide an accessible introduction to the field of animal ethics and the case for taking animal interests seriously. He will explore key concepts such as speciesism, animal exploitation, and wild animal welfare, and will examine the implications of longtermism for animal welfare. Professor Horta will argue that animal advocacy is a crucial cause area that is often overlooked, and will highlight opportunities for academic research to make an impact in this area. This talk will be of interest to anyone who is interested in learning more about animal ethics and the ways in which we can work to improve the lives of animals.