Pia Anderwald (Schweizerischer Nationalpark) mit Seraina Campell Andri und Rupert Palme
Due to species-specific adaptations to different habitat types, chamois and red deer occurring in sympatry at high elevations may show contrasting physiological responses to potential stressors. We examined fecal glucocorticoid metabolites (FGMs) in sympatric Alpine chamois (n=742) and red deer (n=1649) from fresh samples collected in the Swiss National Park with respect to weather, digestibility of forage and human disturbance. Sampling took place at the same locations every two weeks over 4 years. FGM concentrations were determined by enzyme immunoassay. In both species, FGM concentrations were highest in mid- winter and lowest in mid-summer. Numbers of hikers crossing the sampling area on a designated trail in summer (automatically counted by a pyrosensor) had no effect on FGM concentrations in either species. Instead, both chamois and red deer showed a physiological stress response to drought conditions during summer and increasing snow height in winter. In chamois, the response to snow height was additionally modulated by humidity, in red deer by temperature, with greater humidity and lower temperatures, respectively, leading to increased stress. While low forage digestibility was correlated with higher FGM concentrations in red deer in winter and – though only at the lowest elevation sampling area - in summer, it showed no effect on chamois in either season. The main interspecific difference in stress responses was thus related to forage digestibility with chamois apparently better adapted to low quality forage than red deer, but more sensitive to humidity during winter. While the former result is surprising considering the two feeding types (both mixed, but with chamois more on the browsing side), it may reflect the better adaptation of chamois to seasonally poor forage conditions in mountain environments. This would also be in line with the chamois’ higher sensitivity to humidity in winter, i.e. more atypical conditions for alpine habitats.