General description of the project

Our aim is to understand the evolution of behavioral and physiological mechanisms that allow animals to respond adaptively to their changing natural environment. This will also help us to understand how animals can respond to climate change. We use methods from ecology, behavioral ecology, physiology and evolutinary biology to understand how ultimate factors integrate with proximate mechanisms.

During the last decades, intensive field studies have enormously increased our knowledge about mammalian social systems and behavior. However, whereas most of these studies have been performed with large mammals such as primates, carnivores and ungulates, the majority of mammals are rodents, most of them belonging to the family Muridae. Unfortunately, our knowledge about the natural biology of murids is still relatively poor. The Succulent Karoo of South Africa is a semi-desert with rainfall in winter and a wildflower season in spring. This habitat is characterized by bushes, shrubs, ephemerals and succulents. Several small diurnal mammals inhabit this habitat: The striped mouse (Rhabomys pumilio), the bush Karoo rat (Otomys unisulcatus), two species of whistling rats (Parotomys spec.) and the round-eared elephant shrew (Macroscelides proboscideus). The project at this stage concentrates on the striped mouse: So far we collected field data from trapping, direct observations, radio-tracking and videotaping in the nest, which describe the social system of the four-striped mouse (Rhabdomys pumilio) in the Succulent Karoo and tests hypothesis regarding paternal care, group living and communal nesting. The striped mouse is a diurnal murid rodent with an adult body weight of about 30 to a maximum of 80 g. Although striped mice go alone for foraging, they live in groups of 1-4 breeding females, 1 breeding male and their offspring of both sexes, which remain even after reaching adulthood in their natal group, leading to groups of more than 20 adult individuals. Intra-group interactions are typically amicable and take part in the nest and in front of the nest, when group members bask together in the sun during mornings and late afternoons. In contrast, encounters with mice from other groups are aggressive. Adult offspring participate in raising pups, territorial defense and nest building without showing signs of reproductive activity within their natal group, thus indicating helping behavior. The social organization of the striped mouse is highly flexible. In contrast to group living in the Succulent Karoo, the same species is solitary in moist grasslands. During years of very low population density, this solitary social system is also shown by the Succulent Karoo population. At this stage the project concentrates on ecological, proximate and evolutionary reasons of social flexibility, group living and male parental care. The striped mouse is an ideal model to study: Reasons of group living Social flexibility (evolution of, mechanisms) Paternal care Communal nesting/breeding In the future, additional studies will be done on the socio-ecology of the bush Karoo rat and the round-eared elephant shrew.