Weather-dependent changes in habitat use by Alpine chamois.

BACKGROUND: Alterations in weather patterns due to climate change are accelerated in alpine environments, but mountains also provide a wide range of niches and potential refuge areas. In order to identify future critical habitat for mountain ungulates for effective protection, it is important to understand their spatial responses to changing weather conditions without movement constraints by human disturbance. METHODS: Using integrated step selection functions, we investigated fine-scale changes in seasonal habitat use in response to weather and time of day for 55 GPS-collared adult Alpine chamois in summer and 42 individuals in winter in a strictly protected area. RESULTS: Chamois reacted to increasing precipitation and wind speeds primarily by moving to lower elevations in summer and winter. However, reactions to high summer temperatures predominantly involved preferences for increasing tree cover density and northerly slopes. Snow depth had little effect on habitat choice, and southerly slopes were preferred in winter regardless of temperature. At night, chamois moved to steeper slopes and lower elevations than during daytime in both seasons, and to more open areas in summer. Steeper slopes were also preferred with increasing tree cover density. CONCLUSIONS: Chamois employ adaptive fine-scale adjustments in their habitat choice consistent with respect to efficient thermoregulation and protection from both weather extremes and predation risk in summer and winter. Movement responses to climate change are therefore expected to be far more complex than simple altitudinal changes in distribution. Particularly the role of forest cover must not be underestimated, as it appears to provide important thermal refuge habitat from high summer temperatures.

Age-specific survival and annual variation in survival of female chamois differ between populations.

In many species, population dynamics are shaped by age-structured demographic parameters, such as survival, which can cause age-specific sensitivity to environmental conditions. Accordingly, we can expect populations with different age-specific survival to be differently affected by environmental variation. However, this hypothesis is rarely tested at the intra-specific level. Using capture-mark-recapture models, we quantified age-specific survival and the extent of annual variations in survival of females of alpine chamois in two sites. In one population, survival was very high (>0.94; Bauges, France) until the onset of senescence at approximately 7 years old, whereas the two other populations (Swiss National Park, SNP) had a later onset (12 years old) and a lower rate of senescence. Senescence patterns are therefore not fixed within species. Annual variation in survival was higher in the Bauges (SD = 0.26) compared to the SNP populations (SD = 0.20). Also, in each population, the age classes with the lowest survival also experienced the largest temporal variation, in accordance with inter-specific comparisons showing a greater impact of environmental variation on these age classes. The large difference between the populations in age-specific survival and variation suggests that environmental variation and climate change will affect these populations differently.