Computing Biomass Consumption from Prey Occurrences in Scats of Tropical Felids

Abstract

A robust understanding of prey use and selection by carnivores provides crucial insights into their ecology, conservation and management. In majority of the cases, scat analysis is most effective to assess diet spectrum of carnivores, but require correction for potential biases for estimating biomass contribution of different prey items. Since small prey have higher indigestible matter per unit body mas~ due to higher surface area-to-volume ratio, relative frequencies of prey remains in scats do not represent their consumed biomasses. Thus ~ to accurately estimate the proportions of different prey consumed, it is necessary to develop relationships between biomass consumed per field collectable scat and prey weight through feeding experiments. However, no such relationship exists for felids of the Indian sub-continent. The studies on diet of big cats like lion (Panthera leo), tiger (Panthera tigris) and leopard (Panthera pardus) have used a similar relationship based on cougars (Puma concolor) by Ackerman et al. 1984 owing to the unavailability of any species specific relations. Methods: A series of feeding trials were used on Asiatic lion (Panthera leo persica), leopard and jungle cat (Felis chaus) to develop prey incidence to biomass conversion equations (hereafter mentioned as biomass models or biomass equations). Principal findings: All the models showed satiating relationships between biomass consumed per collectable scat and prey weight given by asymptotic exponential functions. However, carnivore specific models when scaled to their respective body weights did not differ significantly between each other, allowing derivation of a generalized biomass model for tropical felids. Inferences using present study models refined existing representation of diet of tropical carnivores. Significance: Results from the present study have strong implications on feeding ecology of tropical felids. Present study refined previous understanding of biomass contribution of different prey species in large felid diet by substantially increasing roportion of medium prey consumption. Such inferences question niche separation of sympatric large felids on the basis of prey species of different sizes, where large carnivores like tiger optimizing on large prey like gaur (Bos gaurus) and sambar (Rusa unicolor). while medium felids like leopard maximizing on chital (Axis axis). Domestic livestock significantly reduced in carnivore diet, reducing livestock depredation rates. indicating lower human-carnivore conflict levels.