Behavioural variation is ubiquitous in the animal kingdom and typically comprises of multiple components — across-individual variation (a.k.a personality), within-individual variation, stochastic noise, and unmeasured variation. Most behavioural research tends to focus on the population mean behaviour, ignoring the aspect of inter- and intra-individual variability. Such variability has been linked to ecological, evolutionary and conservation implications with fitness consequences. Despite the recent explosion in number of studies on animal personality, the focus has been short-term, laboratory-based studies and on a limited number of personality axes.
In this study, I will study variation at the individual level along multiple personality axes, with an in-depth focus on exploratory behaviour and test how this variation links to survival, a crucial component of fitness. I will use the South Indian Rock Agama (Psammophilus dorsalis) as a model system by monitoring and assaying wild individuals throughout their lifespan. I will quantify the different levels of variation by taking repeated measures of each behavioural trait of interest and using variance partitioning statistics.
In my first chapter, I will test whether there are differences in trait variation based on the selection pressure acting on the trait - sexual selection versus viability selection. I expect that the mechanism by which the two selection pressures act would give rise to differences in how variable these traits are. Preliminary results reveal that traits under viability selection tend to exhibit higher consistent differences across individuals.
Taking this result forward, I will focus on a trait under predominantly viability selection - exploratory behaviour. Exploratory behaviour - a measure of response to novelty can have implications for ecology of an organism from foraging performance, habitat selection to mate acquisition and escape from predators. Further, these responses are expected to be plastic across contexts to avoid phenotype-environment mismatch. These plastic responses are expected to have correlations with behavioural types across traits and contexts.
In my second chapter, I will test if there is behavioural differentiation along this axis and how it varies at the intra-individual level. I will use individual responses to novel prey and novel environment as proxy for exploration behaviour and test how this response relates with foraging performance.
In my third chapter, I will look at behavioural plasticity of exploratory behaviour by exposing individuals to different levels of perceived predation pressures and measuring exploratory tendencies. I will also look for evidence of behavioural type-plasticity associations.
Behavioural variation rarely evolves and persists independent of other traits; hence it is prudent to test for fitness consequences by looking at suites of traits. In my fourth chapter, I will test for the presence of correlations between behaviours - exploration, boldness, activity, and social responsiveness (competition and dominance) and check how such a correlation, if existent, affects survival.
Broadly, I will look at the form and nature of inter-individual variation under different selection pressures across time and contexts and test their link to fitness.