Plastic adaptations of foraging strategies to variation in forage quality in Alpine chamois

Abstract

Foraging efficiency strongly affects individual fitness and is influenced by diverse factors such as the food quality and quantity, as well as intra- and interspecific interactions. We investigated whether Alpine chamois (Rupicapra rupicapra L., 1758) in a protected area in the Swiss Alps adapted their foraging behaviour to forage availability and quality by modeling the bite and step rates of individuals on vegetation nitrogen content, relative plant cover, sex, daytime, air temperature and slope. Vegetation characteristics were derived using remote sensing data from airborne imaging spectroscopy datasets and feeding locations determined using a theodolite. Chamois increased their bite rates with decreasing forage nitrogen content, decreasing slope and increasing temperature. Step rates were higher at high temperatures and decreased with increasing relative plant cover. Males showed higher bite rates and lower step rates than females. Daytime had no influence on either bite or step rates. An increase in bite rate may represent a plastic adaptation of foraging behaviour to compensate for lower nutritional quality of the available vegetation. Our results show variability in foraging behaviour according to both vegetation characteristics and the physical environment and emphasize the use of remote sensing data to investigate relationships between habitat and subtle behavioural adaptations in ungulates.