Is nocturnal activity compensatory in chamois? A study of activity in a cathemeral ungulate

Different species exhibit individual daily and annual activity patterns in response to a range of intrinsic and extrinsic drivers. Historically, research on the activity budgets of large wild animals focused on daylight hours due to the logistical difficulties of observing animals at night. Thanks to recent advances in animal-attached technology, however, this research can be extended to a 24-h timeframe. Taking advantage of GPS collars with activity sensors collecting a large amount of data per hour, we separately studied diurnal and nocturnal activity patterns of Alpine chamois (Rupicapra rupicapra), in order to identify the factors affecting them and the correlation between them. From March 2010 to November 2013, we collected data on 17 chamois in the Swiss National Park, a strict Alpine nature reserve where human management was forbidden and human harassment quite rare. Environmental factors were found to significantly influence both diurnal and nocturnal activity rhythms, with temperature and seasonality playing a pivotal role. Surprisingly, we detected a stable peak of activity in the first part of the night, which varied only slightly over the year. In summer, the nocturnal activity of males was inversely correlated to diurnal activity, arguably to compensate for scarce diurnal food intake. Conversely, winter nocturnal activity was positively related to the diurnal activity and served as a cumulative opportunity for energy intake. Chamois showed a weak lunarphilia, with a slight increase in activity levels during moonlit nights, especially during the mating season. In conclusion, our findings denote chamois as a cathemeral species able to adapt its behavioural patterns to match varying environmental conditions.