The role of body size and diet in recent extinctions of southern hemisphere small mammals

Abstract

During the late Holocene, the anthropization of environments associated with European colonization in the southern hemisphere caused drastic changes in native ecosystems, leading to numerous extinctions. Within Mammalia, 75% correspond to small mammals. We explored the hypothesis of the interaction between body size and diet playing asignificant role in their extinction vulnerability. Considering that adaptations to low-protein diets lead to larger body sizes, we propose that this would result in lower fitness for small species with low-protein diets and large species with high-protein diets. We surveyed bibliographic information on 26 southern hemisphere sites generated by the accumulation of owl pellets to assess composition changes of non-flying small mammal (≤ 1 kg) communities in the last 1000 years, compiled diet and body weight data, and assessed their effect on extinction probability using logistic regressions. We modeled extinction probability for species with high and low-protein diets as a function of two body size variables: absolute weight (average adult weight) and relative weight (an estimator dependent on the dietary group and community), with sites as arandom factor. For both models, we were unable to detect a response of extinction probability to body size for high-protein species and found an inverse correlation for low-protein species. Our results highlight the potential of studies focused on small mammals, by suggesting a close relationship between body size, diet type, and extinction probability, where extrinsic factors, such as community composition, would also be relevant.