Thesis Colloquium at CES on 12 June 2019 at 3:00 pm titled "Foraging decisions of the lesser false vampire bat, Megaderma spasma in a heterogeneous landscape" by Harish Prakash from CES,IISc
Predators make various foraging decisions at different spatial and temporal scales. Such decisions can be studied at two levels: patch decisions at the landscape level, and prey decisions at the foraging patch level. In my thesis, I attempted to understand these patch and prey level decisions in the insectivorous bat, Megaderma spasma (lesser false vampire bat), in a human-dominated heterogeneous landscape. I first investigated space use in the context of roost use and foraging locations. Individual bats showed fidelity to both their roost and foraging sites across days. We also found that male bats showed greater foraging range than females, and individuals appeared to have exclusive non-overlapping foraging ranges. Next, I examined if the patch level decisions of the predator were driven by prey resources. I first tested habitat selection of M. spasma at the landscape level. Following this, I observed if the habitat selection was influenced by insect resources. The results showed that bats selected for forest habitats more often than other habitats. However, there was no difference between insect diversity at the order level between forest and plantation habitats. I also investigated if spatial (landscape) and temporal heterogeneity (season) of prey resources and prey vulnerability affects the bat’s diet patterns. The results suggest that seasonality predicts the diet diversity of M. spasma, while landscape does not. I also examined differences in the prey vulnerability faced by the sexes in two bush cricket genera. Lastly, I examined the trade-off between prey detection and localizability and how it affects the predator’s foraging efficiency. Previous studies have shown that predators are attracted towards prey aggregates but face a confusion effect while localizing them. Such studies have however examined predators that use visual cues to detect prey. Results from this study indicated that the acoustically orienting predator, M. spasma showed a preference for calling prey aggregates, but foraging efficiency decreased while localizing, suggesting a confusion effect in the auditory context.