Effet des contraintes environnementales sur la selection de l'habitat de l'orignal (Alces alces) (French and English text).

摘要

Many other variables than food availability are likely to influence behavioural decisions of foragers. The main objective of this research was to relate variations in habitat use patterns of moose with those of the environmental variables known to limit moose populations in north America. More specifically, we hypothesised that selection of forest stands are function of several factors potentially influencing fitness, namely predation, thermal stress and snow depth. To address this hypothesis, it was necessary to obtain frequent as well as accurate locations, independently of weather conditions. We therefore opted for a new and promising but untested technology: a GPS based telemetry system. At a coarse scale, moose used areas where forest stands providing high food availability were intermingled with stands providing shelter. At a fine scale, we located moose approximately 50% of the time in food stands and 50% of the time in cover stands in most annual periods. Females accompanied by a calf showed a higher preference for cover stands composed of conifer trees compared to solitary moose. This preference existed all year round, but it was most obvious during the calving period. These stands provide the highest degree of lateral obstruction which may improve security of the young. Moose preferred to stay less than 50 m from a cover stand when venturing into open areas, even during summer. Doing so, moose may improve the likelihood to escape an approaching predator. The relative preference of moose for mature conifer stands increased in mid- and late winter. Moose may use these stands where snow depth is reduced to facilitate movements. Our results indicate that moose adopt behaviours, especially thermal shelter utilisation and increased nocturnal activity, when thermal conditions are warm. Doing so, moose may reduce the costs associated with thermoregulation. Food availability was not the only variable determining moose habitat use. Habitat selection and activity patterns were also influenced by calf presence, snow depth and thermal environment. Moose showed a trade-off between food availability and exposure to detrimental factors of the environment. (Abstract shortened by UMI.)