Synchrony between individuals or even non-living entities is one of the most striking natural phenomena: from clock pendulums that move in phase to fireflies that flash their light signals together and light up entire trees to crickets, katydids, cicadas and frogs that produce loud, synchronous acoustic choruses. The synchronising calls of species that have been hitherto investigated are however typically simple sound chirps or light flashes that are produced rhythmically at a particular rate.
Gadagkar - 2021 - Experiments in Animal Behaviour - Cutting-Edge Research at Trifling Cost. Indian Academy of Sciences, Bangalore. Access full text of this book at: https://www.ias.ac.in/Publications/e-Books/Experiments_in_Animal_Behaviour
In this book, I introduce readers to the study of animal behaviour by describing simple experiments, both old and new, designed to understand how and why animals behave the way they do.
In most social insect colonies, a single individual, the queen, is privileged to produce offspring while the rest of the members, the workers, spend their entire lives working for the welfare of the colony and rear the queen's offspring. In addition to such reproductive division of labour between the queens and her workers, sub-sets of workers divide non-reproductive labour among themselves, such as working at home versus going out to obtain food, for example. How the members of a colony agree on and bring about an efficient and conflict-free division of labour is of great interest.
The currency of success in nature is the number of offspring you leave behind, so individuals may employ alternative ways to achieve mating success under different conditions. For instance, males may attempt to mate sneakily instead of performing conspicuous courtship displays, which may attract predators. Predation risk is believed to be a factor that can drive individuals to switch between different mating tactics, but this has rarely been studied experimentally.
CES IHS 2020
Talks, Posters, Short documentaries, Panel discussion, Science and Creativity stalls
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 focused 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.
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 summarize, 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.