Using stable isotopes to investigate the seasonal diet of Southern African rodents across natural and Peri-urban landscapes

Abstract

Abstract Dietary studies on wildlife using minimally invasive techniques can elucidate the impacts of anthropogenic activities on ecosystems and native species. Investigating diet-related resource partitioning of biological indicator species can improve our understanding of mechanisms employed by animals to survive in a rapidly changing world. We compared carbon (δ 13 C) and nitrogen (δ 15 N) isotope ratios from hair tissue of four dominant southern African rodent species from the Magaliesberg Biosphere, North West province, South Africa. Hair was collected over three years during both dry and wet seasons across different land-use types: natural and peri-urban. There was significant isotopic variation between the four species across land-use types and seasons. Pairwise post-hoc comparisons of within-site diet proportions showed increased homogeneity of two synanthropic species ( Lemniscomys rosalia and Mastomys coucha ) in the peri-urban site, suggesting exploitation of robust, low-quality grasses and grains. Niche overlap was significantly variable between seasons at the peri-urban site, with an increased intake in grasses and maize grains during the planting and growing wet season, suggesting the rodents are more selective with increased food availability. During the dry season, food sources were shared by two non-commensal species ( Aethomys ineptus and Micaelamys namaquensis ), and the two synanthropic species shared three food sources. Overall seasonal variation across sites may indicate variable diet plasticity in the four generalist species, but specialists in increasingly encroached upon and urbanized seasonal landscapes may struggle to adapt to available food and face extirpation.