Abstracts - Deutsche Zoologische Gesellschaft

108 Behavioral Biology PostersP BB.7 - ENForaging under pressure – seasonal effects of nest predation on lactating volesThilo Liesenjohann, Monique Ellmer, Jana EccardBehavioral Ecology, Universität BielefeldThe relationship of sympatric living species can change with the seasonal availability of food sources.We investigated the impact of season and shrew presence on behavioural adaptations of bank voles(M. glareolus). Both species live in the same habitat, but while bank voles feed on insects and grains,shrews are insectivores, scavengers and nest predators. At high vole densities, shrews concentrate onnestlings, thus lactating bank voles should be highly sensible to shrew presence. But whereas in summerfood is frequent, resources diminish in autumn, enhancing the pressure on feeding for survival.Wereleased females with new born pups in fourteen ¼ ha outdoor enclosures in Central Finland and addedshrews (S. araneus) as treatment. We analysed feeding behaviour in artificial food patches located ina grid around the nest side. The experiment was repeated in summer and autumn 2007.Vole mothersresponded to shrew presence by using a lower number of feeding stations, but taking a higher percentageof their total intake from fewer trays. The total amount of food taken from the feeding stations wasdepending on shrew presence as well, but only in the summer replicate. In autumn voles where relianton the resources provided and shrews had no effect on the total intake. Supporting these results, a lowernumber of the offspring was recaptured from the shrew enclosures in autumn, indicating the voles´trade off between nest protection and nutrition in the late season.P BB.8 - ENThe influence of social stress on susceptibility and severity of a collagen-inducedarthritis (CIA) in male wistar ratsKerstin Schunke 1 , Christine Wolff 2 , Rainer H. Straub 2 , Volker Stefanski 31Lehrstuhl Tierphysiologie, Universität Bayreuth; 2 Department of Internal Medicine, UniversityMedical Center, Regensburg; 3 Leipniz Institute of Zoo and Wildlife Research, BerlinRheumatoid arthritis (RA) is a multi-factorial autoimmune disease whose aetiology and progression isinfluenced by a range of immunological, neuroendocrine, and psychosocial factors. Social stress hasbeen shown to influence the endocrine and immune system and may therefore play a role in RA. Theaim of our study was to investigate the effects of social stress on susceptibility and severity of a collagen-inducedarthritis (CIA) in male Wistar rats. Psychosocial stress was induced by continuous confrontationwith resident male opponents for seven days. Control males remained undisturbed in theirhome cages. On day 4 of confrontation, arthritis was induced by injection of collagen type II. Behavioralanalysis and a regular assessment of the clinical symptoms was conducted. Furthermore, bloodsamples for physiological measurements were taken. The data show that all intruders became clearlydefeated. Social defeat as well as induction of CIA was associated with many immunological and endocrinologicalalterations. Control animals developed more often disease than stressed rats. However,when stressed rats developed arthritis, we observed an earlier disease onset with more severe arthritisthan control rats. These data show that social stress leads to a reduced susceptibility to CIA, but on theother hand, it aggravates the disease in animals which are diseased. We hypothesize that stress causesa stronger innate immune response, which is deleterious during the immunization phase.