Assessment of diet and abundance of large carnivores from field surveys of scats
Published in - Thesis submitted to the Manipal Academy of Higher Education (Deemed University), 2006
ABSTRACT: Reliable monitoring of tiger populations requires estimation of absolute abundance, or at least relative abundance, using rigorous sampling-based methods. In this study I developed field sampling protocols for collecting tiger scats for purposes of generating estimates of abundance from closed model capture-recapture sampling, based on possible identification of individual tigers from their fecal DNA. The field protocol involved a six week ‘closed’ survey period, six sampling occasions of seven days each that covered a 671 sq. km. of Bandipur Tiger Reserve, India, using 18 sampling routes. The protocol reasonably mimicked survey protocols used in photographic capture-recapture sampling in the same study area. The scat survey yielded more ‘captures’ than the photographic survey. The scat survey data were additionally used to derive a scat-encounter rate index for estimating relative abundance of tigers.
I also conducted a field study of diets of three sympatric large carnivores- tiger, leopard and dhole in Bandipur Tiger Reserve, India based on analyses of 381, 111 and 181 scat samples respectively. Simple frequency of occurrence of prey items in predator diets were converted to relative biomass and numbers consumed using regression equations from earlier studies. The results showed that although these three predators kill 11-15 species of vertebrate prey, relatively abundant ungulate species provided 88-97% of biomass they consume. The largest of ungulates, gaur and sambar provided 73% of biomass consumed by tigers, whereas medium sized chital and wild pig formed, respectively, 65%, and 83% of the biomass intake of leopards and dholes. The results of the study, in conjunction with earlier work, supports the prediction that abundance of ungulate prey species, as well as their availability in different sizes classes, are both critical factors in facilitating sympatry among these three predator species.