Carcass utilization by tigers : implications for calculating prey requirements

Abstract

Fewer than 3,500 tigers (Panthera tigris) remain in the wild. Habitat loss and fragmentation, and depletion of prey are key factors contributing to their decline, prompting investigations on prey requirements needed to sustain their dwindling populations. To estimate prey requirements from consumption rates the Non-Consumed Portion of a carcass (NCP) or degree of carcass utilization is required, as depending on prey size part of the kill might not be consumed. Because NCPs for tigers have never been systematically estimated, the aim of this study was to develop a model to calculate NCPs based on prey body mass, and to determine whether the NCPs used in current tiger literature were accurate. Additionally, we applied the model to two tiger reserves to test if our results improved prey requirement estimates calculated with current NCPs. The study took place at Laohu Valley Reserve (South Africa), where four male and five female tigers were fed fresh carcasses of six ungulate species. Each prey carcass was weighed prior to feeding to tigers and once abandoned, the remains were weighed allowing the weight consumed minus the gastrointestinal contents to be calculated. We observed a strong positive relationship between prey body mass and NCP. For large prey, prey requirement estimates obtained with the NCPs yielded by our model were very similar to those obtained with the NCPs used in current tiger literature. However, differences increased for smaller prey, and for those species that comprised a high percentage of the tiger diet. In summary, we provide a model to calculate NCPs based on prey body mass, and demonstrate the importance of using specific values of NCPs in calculating prey requirements from consumption rates. These results could be useful for other large carnivores, as well as for calculating feed portions for large predators in captive settings.