Recent advances in technology and quantitative methods have led to a growth in our ability to study mobile animal groups in their natural environments. Understanding the movement patterns of these groups requires the study of individual movement behaviour and the interactions between leadership, imitation, and environmental drivers that influence movement decisions. In this talk I will also discuss the methods we're using to investigate these questions in the field, including tools to collect video footage, computational methods to locate animals within images, and statistical techniques to infer behavioral rules from movement data for both individuals (GPS collar data) and social groups (from UAV footage).

Many regions are experiencing unprecedented change in their climatic conditions. Temperature and precipitation are the major determinants of vegetation structure and biomass. Understanding how vegetation respond to change in temperature and precipitation will be key for predicting the status of the terrestrial Carbon sink and many interconnected ecosystem responses under future climate scenarios. In my study, I analyze long-term data sets at different spatial scales to identify patterns and processes of interactions between climate and vegetation.

In my first chapter, I address growing concerns of vegetation degradation in the Trans-Himalayas. This cold-arid ecosystem is a climate-change hotspot because it is experiencing rapid rise in temperature, and is also getting progressively wetter. While warmer and wetter conditions may favor plant growth, yet, there are widespread concerns of degradation in this ecosystem. I evaluated whether long-term trends in vegetation change, i.e., greening or browning, can inform management concerns over degradation. I analyzed satellite-derived vegetation datasets (NDVI) at six spatial scales: MODIS (250 m, 500 m, 1 km, and 5.5 km), SPOT (1 km), and GIMMS (8 km). Results indicate browning (degradation) in the spring and greening in late summer. This pattern was consistent across all spatial scales. The timing and location of degradation did not coincide with human land-use (livestock grazing), suggesting vegetation trends may be more strongly related to climate than to human land use. Overall, the results show the importance of evaluating the consistency of inter- and intra-annual vegetation trends across different spatial/temporal scales for interpreting degradation.

In my second chapter, I address how spatial and temporal variation in climatic factors can influence vegetation phenology across the greater Trans-Himalayan landscape. Global warming has caused relaxation of thermal constraints for plant growth in cold regions, which include both high-altitude and high-latitude landscapes. However, this hypothesis has found poor support globally, including the Trans-Himalayas where temperature alone could not explain the long-term greening/browning patterns. An alternate hypothesis is to examine the effect of water limitation across the Trans-Himalayan landscape. I investigated this by analyzing the plant phenological response in terms of change in shape of the annual growth pattern – a unimodal curve that is represented mathematically by a double-logistic function. I analyzed long-term changes in geometric properties of vegetation phenology, e.g., skewness and kurtosis of the double-logistic curve. This long-term phenological analysis showed that the plants are reaching their peak biomass earlier in the growth season, and also attaining a higher peak biomass. These changes were explained by variation in snowfall and rainfall. This study shows the differential effect of snow and rain in determining the phenological trends in mountain ecosystems.

In my last chapter, I explore whether long-term trends in global vegetation change is linked to thermal constraints on the biochemical steps in photosynthesis. A key aspect is temperature-sensitivity of net photosynthesis, which declines above 32 oC due to thermal sensitivity of participant enzymes, particularly Rubisco Activase. I find that warming over the past four decades has altered the window of thermally suitable days for photosynthesis and plant growth, through effects attributable to this enzyme’s thermal-sensitivity. This explains satellite-records of long-term vegetation trends during 1982-2015 (greening/browning) for nearly 80-million km2 across the world Change in temperature was more successful in explaining vegetation trends than simultaneous change in water-stress over the same period. This match (Bayesian probability) between thermal-sensitivity of enzymes and vegetation response could not be achieved by random chance. Comparatively, match against browning was lower than for greening, due to confounding effects (pests, fire, logging). However, I found that the water-stress could reverse the trends expected from temperature, especially in the warm regions. These results can help improve our understanding and prediction of future changes in terrestrial productivity, and the fate of the terrestrial carbon-sink, as they link processes occurring at molecular and planetary scales.

Many eukaryotic hosts are associated with microbes that enhance their fitness. The establishment and maintenance of such relationships likely depends on the faithful transmission of beneficial microbes across generations. However, in some cases the microbes are not maternally transmitted, but are environmentally acquired. Thus, when hosts disperse to new habitats or switch to a new diet, they may not have access to the appropriate microbes, leading to reduced fitness. In such cases, can the host establish new microbial partnerships, and are they specific? More generally, how are microbial communities assembled, and (how) does host association influence this process? In this talk, I will discuss our efforts to address these questions in different natural and laboratory insect populations.

Life history evolution is central to evolutionary biology. It deals with the schedule of reproduction and mortality over lifetime and attempts to understand the variation in the timing and frequency of reproduction and allocation of energy to reproduction, growth and maintenance. In this teaching lecture, I will cover the fundamental aspects of life history theory, place it in the context of natural selection and discuss its scope. I will then consider the major life history traits: age and size at maturity, number and size of offspring, and reproductive life span and ageing. I will then explore life history strategies using insects as an example. Finally, I will discuss limitations and paradoxes associated with these concepts. This talk will aim to give a broad and conceptual introduction to the theoretical body of work dealing with the evolution of life histories.

Resident microbes and the microbiome (collective microbial genomes associated with individuals) can provide novel functional benefits to their hosts. In insects, microbial associations mediate host adaptation to abiotic and biotic stresses and are important contributors to the insects’ remarkable ecological success. This talk will highlight the microbiome’s role in insect dietary specialization and in their utilization of challenging breeding resources. I will present my research on microbiome-mediated usage of unconventional and potentially noxious diets such as carrion and dung that are ephemeral and select for rapid development. Despite being susceptible to microbial spoilage, carrion beetles and dung beetles prolong the palatability of these diets to support larval development and are immune to any ill effects of feeding on decomposing matter. I will discuss the importance of the microbiome in the nutritional ecology of these insects, its implications on host diversification, behavior, and regulation of ecological processes.

Intense competition among individuals of the same sex and species can result in striking, elaborate and costly traits. Such intrasexual competition has been widely studied among males; but it is only in the last few years that intrasexual competition among females has received attention. Recent reviews suggest that competition between females may be widespread; females may compete over a variety of resources including mates, food, nesting sites and safety; and such competition can have important behavioural and evolutionary consequences. However, systematic studies of intrasexual competition among females are scarce. Consequently, our understanding of the form that competition takes in females and the traits that evolve under such competition is limited. Owing to differences in life histories, the patterns and processes acting in female-female competition are expected to be different from those in males. In my thesis, I have focussed on studying traits and strategies in intrasexual competition in females in a polygynous species, the tropical rock agama (Psammophilus dorsalis), through observations and experiments in the wild.
The social system plays an important role in establishing the contexts in which various behaviours are played out. Establishing the social system of a population is essential for investigating the ecology and evolution of behavioural and life history traits. Thus, first, I studied the nature of between- and within- sex interactions across the lifetime of individuals in Peninsular rock agama using space use patterns. Individually tagged wild males and females were closely monitored and their home ranges estimated. Male home ranges overlapped multiple female home ranges, but females defended exclusive home ranges, suggesting strong competition.
I then examined signalling traits, which, observations on males suggest, play a key role in conveying information both in direct contest competition and in indirect competition to attract mates. I observed wild individuals every month across their lifetime to study the extent of female signalling and to understand the contexts in which the different signals are used. I also examined whether signalling rates are correlated with proxies of female fitness. I report that females, too, have a complex signalling repertoire. My findings suggest that females may signal both in direct competition in sexual and non-sexual context and to attract mates. Results also hinted towards correlation between signalling rates and some fitness proxies.
Finally, I examined strategies of female-female competition. Because of their investment in young, the costs of overt competition, such as conspicuous signalling and physical aggression, are expected to be comparatively high for females. Therefore, females should normally signal using relatively inconspicuous traits. They should be sensitive to the perceived threat, more so than males, and escalate to costly signalling and aggression only when the threat is high. I tested this hypothesis using field experiments and by simulating intruder threat on territories of wild female P. dorsalis. I report that in the normal signalling context, females signal using less conspicuous signals, less conspicuous than in males. I also show that females strikingly increase response in the form of signalling and aggression with increasing level of intruder threat. To summarise, I find substantial intrasexual competition in females of a polygynous species. Traits and strategies can be complex and different from that of males. Finally, owing to the cryptic nature of competition, an experimental approach might be key in studying competition between females.

India has among-st the highest burden of canine-mediated rabies in the world. India also has among-st the highest numbers of free-ranging dogs in the world, a lax dog ownership policy, and animal rights laws that conflate population management with rabies control. The failure to control rabies in India is a multi-faceted problem: a lack of systematic surveillance, limited knowledge on rabies dynamics in multi-host systems and poor implementation of mitigation measures. In this talk, I will explore the various facets of this problem, and show how a OneHealth approach that integrates Ecology allows for a better understanding of rabies dynamics in India and the development of targeted intervention techniques.

Himalayan gray langur is a little-known endangered primate, endemic to Himalayas. Its distribution and ecology are poorly known. In Kashmir and adjoining regions, it is likely at risk of extinction due to land use change and conflict with humans. In my thesis I assess the current distribution of this species in Kashmir and try to understand how this species copes up with seasonality in terms of food availability, quality and temperature differences.
In the first part of my thesis, we, aimed to ascertain the current distribution of this species in Kashmir and identify sites which face human-langur conflict. Using well-structured questionnaire and on-ground surveys we have attempted to determine the spatial distribution in Kashmir region. Results suggest Himalayan gray langurs to be distributed in two different habitat types dominated by broad-leaved deciduous forest and coniferous forests within an elevation range of 1700-3000 m. There was found little conflict in the area based on the questionnaire surveys conducted. Conservation education and awareness programs in schools and colleges were conducted throughout to impart knowledge about the existence of this primate species in their region.
Second part of my thesis involves understanding activity patterns and time budgeting in different seasons. Activity budget is an important component as it determines how animals interact with their environment by adopting various behavioural strategies to maximize energy and reproductive success. Various factors are known to effect activity patterns in primates such as food availability, quality, and temperature, etc. These factors influence the time allocation on different daily activities. Food availability is known to either increase or decrease the time primates spend on feeding and resting. In the case of Himalayan gray langur, it is expected to increase feeding time in winter when food available is scarce. Increasing time of feeding helps them thermoregulate in sub-zero temperatures. From the study, similar results on seasonal time budgeting were obtained. As far as daily activity budgeting was concerned, two feeding peaks during winter were observed, in the morning and evening. During summer, only one feeding peak was observed in the afternoon. This discordance may be explained by analyzing their diet and other environmental factors.

Thesis Colloquium

Male reproductive success can be driven by male mating effort in sexual signaling and in the benefits transferred to females during mating via nuptial gifts. Male mating effort, itself can be determined by various biotic and abiotic factors, such as nutrition quality, age, body size, mating status and temperature, contributing to the immediate condition of the male. In systems that involve long distance acoustic signaling by males for mate attraction, in addition to male mating effort, female motivation to acoustically localize a potential mate can also impact male reproductive success. Female motivation can again be governed by female condition. In my thesis, I studied the condition-dependent signaling and mating behaviour in an acoustically communicating tree cricket species, Oecanthus henryi. The first two chapters examine condition dependence of male mating effort in terms of male signaling and nuptial feeding respectively. In the second chapter, I also measured spermatophore attachment duration as a measure of male reproductive success. My results suggest that diet quality is an important factor in determining the male investment. Males reared on better quality adult diet had a higher lifetime and nightly signaling effort which would imply better mate attraction potential. In the mating behaviour, with increasing age males on high-quality diet had longer spermatophore attachment duration (SPAD) which can indicate higher sperm transfer and hence, higher fitness. Smaller males, received the least reproductive benefit in terms of SPAD across age and diet.
O. henryi males additionally exhibit a unique tool making behavior called baffling which increases their signal loudness. The gain in loudness is known to bestow a higher reproductive benefit (SPAD) to small males which are otherwise less preferred during mating. In the third chapter, we investigated the condition-dependence of this signaling strategy and found smaller males on better diet to have higher baffling probability. This result suggests that baffling is an energetically expensive alternate tactic used by the less preferred males possibly to improve their reproductive fitness.
In the final chapter of my thesis, I aimed to understand the effect of female dietary condition and mating status on female mate search and mating behaviour. Interestingly, female mating status and not diet turned out to be a key driving factor in this context. Despite a high remating propensity, mated females showed significantly low motivation to perform phonotaxis. Besides, both nuptial feeding duration and spermatophore attachment duration decreased in mated females. Thus, for a male it is more advantageous to mate with an unmated female. This highlights the importance of the proportion of virgin females in the wild population in relation to male reproductive success. Moreover, it could potentially determine sexual selection pressures in the system by introducing the additional competition in males for unmated females.