Eco-physiology of a socially flexible mammals living in a semi desert.

• Applicant: Professor Dr. Carsten Schradin
• Subject Area: Animal Physiology and Biochemistry
• Term: from 2011 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 191018853

Understanding how evolved endocrine mechanisms allow animals to behave adaptively in their changing natural environment is the main goal of the proposed project. The focus will be on physiological mechanisms regulating metabolism (testosterone and corticosterone), reproduction (testosterone and estrogen receptor α), and osmoregulation (arginine vasopressin). I will study how these physiological processes respond to environmental changes, how these changes in hormone secretion regulate social behavior, and the resulting fitness consequences. I will make intraspecific comparisons between individuals of one species within one population differing in social behavior. My study species, the striped mouse (Rhabdomys pumilio) from South Africa, is a generalist living in moist and arid habitats. Striped mice show high social flexibility: they can live solitarily or in extended family groups. My study population lives in an arid environment with pronounced differences in the annual dry season. First, I will take physiological measurements from free living individuals. Samples for measuring hormone levels will be available for 7 years (2008 – 2014), during which time there has been pronounced variation in the amount of rain during the dry seasons. I will correlate these physiological measurements with food and water availability and social behavior. I will further test the hypothesis that high levels of metabolic hormones lead to fitness benefits in years with significant rainfall during the dry season but to reduced survival in years with pronounced dry seasons. Such observations may explain the maintenance of variation within the population. Experimentally, I will provide water during the dry season to test for an influence on metabolism, arginine vasopressin levels and social behavior. Second, in captivity and in the field I will experimentally induce the observed physiological changes under standardized conditions by using hormone implants as well as antagonists. I will measure changes in physiological parameters and in social behavior. Third, I will study how environmentally induced variation in hormone levels influence brain function, especially arginine vasopressin production and the expression of estrogen receptor α, factors known to influence social behavior. The proposed project will integrate studies on behavior, ecology and physiology, combining both ultimate and proximate research to understand adaptive modification of social behavior. Additionally, we will gain insight into how a species that also occurs in moist habitats reacts physiologically and behaviorally to droughts, which are likely to become more frequent in the future as a consequence of climate change.

• DFG Programme: Research Grants