Nocturnal activity of a “diurnal” species, the northern chamois, in a predator-free Alpine area

Abstract

The reduction of predation risk is widely considered a major factor affecting the nocturnal activity of mammals. Furthermore, on precipitous mountain terrain, moving in very poor light conditions should be avoided by animals with no special eyesight adaptation to darkness. The Northern chamois Rupicapra rupicapra has been for long considered as a diurnal species, with occasional nocturnal movements. For the first time, we have quantified the nocturnal activity of 21 radiotagged female chamois from the Italian Eastern Alps (Paneveggio-Pale di San Martino Natural Park), continuously monitored for two years from sunset to sunrise, with 24h tracking sessions carried out for six months. Large predators were not present in the study site. Despite their mainly diurnal activity pattern, peaks of nocturnal movements were detected throughout the year. The least proportion of active night fixes occurred in January and in July, while the most were in April and in October. The greater nocturnal activity in the warm months compared to cold periods, was probably due to frozen snow cover reducing nocturnal movements. Movements were mainly concentrated in bright moonlight nights, possibly because of the absence of large predators, but more likely because of increased visibility. Changes in activity levels throughout the year may also reflect changes in energy requirements of Northern chamois.