ANR COBESOLI

Solitary living has traditionally been regarded as the primitive default condition in mammals. However, our recent research indicates that solitary living is not an ancestral but derived state. We cannot understand ecological and evolutionary reasons of group-living, if we do not understand the costs and benefits of the alternative, which is solitary living. Multiple socio-ecological factors influence the costs and benefits of solitary living. Here we will focus on the prediction that solitary living reduces daily energy consumption by reducing competition. We will study the bush Karoo rat which builds extensive stick lodges, creating a micro-climate that is predicted to mitigate the costs of solitary living, especially the absence of thermoregulatory benefits through huddling. We will measure temperatures and humidity inside and outside lodges. We will then measure the rats’ metabolic rates at these temperatures. We will be the first to use mini-GPS data loggers on a small rodent and combine this with the doubly labelled water technique to measure total daily energy expenditure depending on daily distances travelled and home range size. We will compare this between solitary and the 5% of the population that is group-living. We predict significantly lower metabolic rates at temperatures measured inside occupied lodges. We predict lodges to be inherited along genetic matrilines, so that the huge investment into building and maintaining lodges leads to direct and indirect fitness benefits. While our study focusses on a single species, this will inspire additional research of solitary mammals, for which not enough data are available currently for good comparative studies. Understanding the evolution of solitary living is essential to conserve mammalian biodiversity. Our project will transform our understanding of mammalian social evolution by providing insights into how solitary living leads to energy savings and increased inclusive fitness.

LSCE contribution: LSCE will provide key answers to questions about how lodges are inherited, passed on and restored.