Adding constraints to predation through allometric relation of scats to consumption. (25th March 2016)

• Record Type: Journal Article
• Authors: Chakrabarti, Stotra; Jhala, Yadvendradev V.; Dutta, Sutirtha; Qureshi, Qamar; Kadivar, Riaz F.; Rana, Vishwadipsinh J.
• Editors: Fryxell, John
• Is Part Of: Journal of animal ecology. Volume 85:Number 3(2016:May)
• Page Start: 660
• Page End: 670
• Publication Date: 2016-03-25
• Subjects: carcass utilization -- obligate carnivore -- optimal foraging -- predator–prey interaction -- prey digestibility -- prey preference -- tropical felids; Animal ecology -- Periodicals; 591.7
• DOI: 10.1111/1365-2656.12508
• Languages: English
• ISSNs: 0021-8790

Abstract

Summary: A thorough understanding of mechanisms of prey consumption by carnivores and the constraints on predation help us in evaluating the role of carnivores in an ecosystem. This is crucial in developing appropriate management strategies for their conservation and mitigating human–carnivore conflict. Current models on optimal foraging suggest that mammalian carnivores would profit most from killing the largest prey that they can subdue with minimal risk of injury to themselves. Wild carnivore diets are primarily estimated through analysis of their scats. Using extensive feeding experiments ( n = 68) on a wide size range (4·5–130 kg) of obligate carnivores – lion, leopard, jungle cat and domestic cat, we parameterize biomass models that best relate consumption to scat production. We evaluate additional constraints of gut fill, prey digestibility and carcass utilization on carnivory that were hereto not considered in optimal foraging studies. Our results show that patterns of consumption to scat production against prey size are similar and asymptotic, contrary to established linear models, across these carnivores after accounting for the effect of carnivore size. This asymptotic, allometric relationship allowed us to develop a generalized model: biomass consumed per collectable scat/predator weight = 0·033–0·025exp −4·284(prey weight/predator weight), which is applicable to all obligate carnivores to compute prey biomass consumed from scats. Our results also depict a relationship for prey digestibility which saturates at about 90% for prey larger than predator size. Carcass utilization declines exponentially with prey size. These mechanisms result in digestible biomass saturating at prey weights approximately equal to predator weight. Published literature on consumption by tropical carnivores that has relied on linear biomass models is substantially biased. We demonstrate the nature of these biases by correcting diets of tiger, lion and leopard in recent publications. Our analysis suggests that consumption of medium‐sized prey was significantly underestimated, while large prey consumption was grossly overestimated in large carnivore diets to date. We highlight that additional constraints of prey digestibility and utilization combined with escalating handling time and risks of killing large prey make prey larger than the predator size unprofitable for obligate carnivores. Abstract : From results of feeding trials conducted on a wide size range of tropical felids, the authors develop a unified model to convert prey occurrences in scats to biomass consumed. The authors revisit some fundamental premises of predation ecology and question classical notions on optimal prey choice by carnivores. Due to constraints of gut fill, passage time and carcass persistence, predators benefit little from prey larger than themselves. The authors feel that the results are globally relevant to carnivore ecology and will help to gain a better understanding of prey consumption and prey choice with improved rigour.