Evidence from recent studies on foraging behavior supports the idea that animals optimize for multiple macronutrients and not just energy gain. Such optimization requires animals to know three things – 1) their current nutritional state, 2) nutritional composition of the food item, and 3) how much of the food item is needed to achieve the desired nutritional state. Lab experiments on animals across taxa demonstrate that they can, in fact, achieve this feat. We now also know that optimal nutritional composition of diets, or ‘intake targets’, are plastic, which allows animals to maintain homeostasis under changing environmental conditions. Abiotic factors (such as temperature) and trophic interactions (both bottom-up and top-down) not only affect the nutritional demands, but also constrain acquisition of nutrients in response to those demands. In addition, life-history strategies such as foraging modes might also influence nutritional demands, and therefore, intake targets. Under natural conditions, however, such constraints often prevent animals from achieving these targets.

In many habitats, available resources vary temporally with seasons and spatially across the landscape. Along with these bottom-up constraints on nutritional intake, top-down predation risk effects also affect foraging behavior and nutrient acquisition in the prey species. In a desert ecosystem such as the one in the Thar, an herbivorous agamid, the Indian spiny-tailed lizard Saara hardwickii, experiences great spatio-temporal variation in resource nutritional quality. Temporal variation in temperature and spatial variation in predation risk are also prominent stressors and can influence foraging in these lizards. This provides an opportunity to understand nutritionally explicit foraging decisions in response to environmental factors varying in both space and time. In my thesis, I propose to examine the nutritional intakes of S. hardwickii in response to temporal shifts in nutrient state space and temperature. I will also capture the variation in distribution of nutrients in space to construct a ‘landscape of nutrition’ (LON) for the spiny-tailed lizards. Lizard burrow densities and body condition index will be measured to understand burrow site selection and its consequences along the landscape of nutrition. In addition, I will quantify predation risk to construct a ‘landscape of fear’ (LOF) in the same space. Along the LON and LOF, I will examine various behavioral, nutritional, and physiological variables to understand animal responses as they balance foraging benefits and predation risk. Further, in a manipulative experiment, I will examine the consequences of long-term nutritional constraints on physiological and motor performance. Finally, using published literature on diet composition, I will explore how life-history strategies such as foraging modes shape intake targets over evolutionary timescales in animals across taxa.

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Species interactions are known to shape biological communities. While antagonistic interactions like competition and predation are well known, cooperative interactions have received comparatively less attention. Mixed-species foraging behaviour is a common phenomenon seen across various taxa including fish, birds and mammals, where different species form groups and forage together. Unlike symbiotic associations, these interactions are more dynamic and include a much larger subset of species of the community. We sampled mixed-species groups (MSG) of reef fish in the Lakshadweep islands, off the west coast of India. The data was gathered over four years following a mass-bleaching event which led to massive loss of coral in Lakshadweep in 2010. Though not widely reported, we discovered that mixed-species grouping is a common occurrence in the reef ecosystem. Around 130 of the 305 commonly observed species of fish in the Lakshadweep were seen participating in groups to some extent. Using a cluster analysis on species composition, we categorised the groups that were observed in Lakshadweep into nine compositional categories, which also exhibited variation in behaviour, habitat affinity and group cohesion. We then examined variation in grouping propensity, species richness, species evenness as well as species composition across space, time and habitat for the most commonly observed compositional categories. We found that invertivores tended to form smaller attendant groups, with clear nuclear-follower relationships, and likely form for direct foraging benefits. Herbivorous fish on the other hand formed large shoaling associations indicating benefits gained from increasing group size. We found evidence of the effect of the mass-bleaching event and subsequent ecosystem recovery on the formation of some groups. Reef fish MSGs are thus important components of these ecosystems and can both affect and be impacted by reef structure and function.

Collective movement is a fundamental process affecting the survival and reproductive success of group-living animals. Many of the hypothesized benefits of grouping such as predation evasion and foraging efficiency require the individuals in a group to move in a coordinated way. While moving in groups, animals are not only responding to the environment but also interacting with each other. These interactions give rise to emergent collective movement and behavioural patterns. A novel aspect of emergent behaviour is that a group can exhibit properties that no individual displays on its own. 

Most studies on emergent properties of collective behaviour are conducted in controlled conditions. However, in natural settings, habitat is heterogeneous in terms of resource distribution, availability of hiding places and substrate for movement. Empirical studies have rarely investigated such fine-scale interactions (e.g. alignment, attraction among individuals) in their natural habitat. One reason for the dearth of such studies is the difficulty of data collection. Recent advances in techniques of aerial imagery allow us to observe and record such fine-scale data. For my PhD project, I studied the collective behaviour of blackbuck herds in their natural habitat. More specifically, I investigated the collective response of blackbuck herds during predation-like events. By analyzing multiple interactions among group members simultaneously, I aimed to understand the role of social interactions in shaping the collective response of blackbuck herds when faced with predation-like threats. 

First, we overcome the difficulty of observing fine-scale interactions in animal groups (in their natural habitat) by using UAVs. We recorded blackbuck herding behaviour at high spatio-temporal resolutions (30 frames per second). Using this technique we were able to record the blackbuck herd’s collective escape behaviour in the context of predation using controlled-simulated threats.

Tracking animals in the videos recorded in natural habitat is extremely difficult due to varying background and light conditions and clutter in the background. Relatively basic image processing methods and default tools don’t perform satisfactorily in such a scenario. 

Hence, we developed a machine learning method and GUI tool to extract the spatial locations and movement trajectories of all the individuals in a group from the videos recorded in natural field conditions.

Once we were able to obtain the movement trajectories from the videos, I then analysed these trajectories and interactions between individuals to explore - how the information about predatory risk spreads through a group in natural conditions. Broadly, our results suggest that transient leader-follower relationships emerge in these groups while performing the high-speed coordinated movement. Also, males and females respond differently to the threat scenario: adult females are more likely to be the response initiators whereas adult breeding males are more likely to influence the group movement during the escape response. Our results indicate that in fission-fusion groups associations are likely to last for short time scales and spatial positions of the individuals only affect their response-time (vigilance behaviour) but not their influence on the group. 

Many insects such as ants, bees, wasps and termites organise themselves into societies with division of labour, communication, conflict, cooperation and altruism. Insect societies resemble human societies in many ways and are arguably more efficient than ours in some ways. They sustainably harvest environmental resources, engineer their environments both inside and outside their nests, practice agriculture, fight disease with a combination of individual and social immunity, organise social hunting parties, navigate their environment using terrestrial and celestial cues and majorly influence the evolutionary trajectories of other organisms such as flowering plants. So, can we humans learn anything from insect societies? In this talk I will attempt to answer this question in the affirmative, but with caution. I will consider such relatively non- controversial topics as communication, agriculture and robotics but also some relatively controversial topics such as cooperation, conflict, collective decision making and democracy.