Predation risk and foraging behavior of the hoary marmot in Alaska [Risque de prédation et comportement d'afourragement de la marmotte d'Alaska].

Résumé

La disponibilité des ressources alimentaires conjointement au risque de prédation influence l'utilisation du site d'alimentation par M. caligata. Ces facteurs doivent être considérés quand on établit un modèle du comportement d'approvisionnement d'espèces qui peuvent être simultanément prédateur et proie. I observed hoary marmots for three field seasons to determine how the distribution of food and the risk of predation influenced marmots foraging behavior quantified the amount of time Marmota caligata foraged in different patches of alpine meadows and assessed the distribution and abundance of vegetation eaten by marmots in these meadows. Because marmots dig burrows and run to them when attacked by predators marmot-to-burrow distance provided an index of predation risk that could be specified for different meadow patches. Patch use correlated positively with food abundance and negatively with predation risk. However, these significant relationships disappeared when partial correlations were calculated because food abundance and risk were intercorrelated. Using multiple regression, 77.0% of the variance in patch use was explained by a combination of food abundance, refuge burrow density, and a patch's distance from the talus where sleeping burrows were located. Variations in vigilance behavior (look-ups to search for predators while feeding) according to marmots ages, the presence of other conspecifics, and animals proximity to their sleeping burrows all indicated that predation risk influenced foraging. In a forage-manipulation experiment, the use of forage-enhanced patches increased six-flod, verifying directly the role of food availability on patch used. Concomitant with increased feeding, however, was the intense construction of refuge burrows in experimental patches that presumably reduced the risk of feeding. Thus, suggest that food and predation risk jointly influence path use by hoary marmots and that both factors must be considered when modeling the foraging behavior of species that can be predator and prey simultaneously.