Morphological and behavioral adaptations of moose to climate, snow, and forage

This thesis focuses on the behavioural and morphological adaptations of moose to snow and climate: specifically, seasonal migration, habitat choice, and following behaviour, plus the relationships among morphology, climate, snow, and seasonality. I examine intake and availability of winter forage, and perform one of the first large-scale tests of a widely used optimal foraging model by videotaping free-ranging moose making their own choices. The study of seasonal migration and habitat choice showed that the effect of snow differs with variation in snow severity: in locations with large differences in snow depths in a short distance, snow depth is important, but in locations where snow depth is less variable, snow quality emerges as more important. The thesis is one of the first to use a new method to evaluate the importance of snow quality. Testing between competing hypotheses to explain morphology, the importance of snow was further emphasized relative to temperature and latitude. In snowier areas, moose had larger hooves and longer legs than expected from their size and age. Morphology both conformed to, and was in opposition to some of the most well-known ecogeographical rules: in areas with cold winters, moose were heavier (Bergmann’s rule) and had shorter ears (Allen’s rule). There was also some evidence that moose morphology was related to heat stress during summer. The quality of the two main winter forages (birch and willows) differed within and between species. Willows had more available browse, and lower levels of secondary defence compounds than birch, but also less nitrogen and more fibre. These differences in forage quality also emerged in the test of the Spalinger-Hobbs model, as moose preferentially fed on willow, which was also the faster food to ingest. Most importantly, the analysis revealed that the foraging parameters varied within a foraging bout, and thus parameterizing the model from only the first few minutes of a bout would greatly mis-estimate intake. In the face of climate change, my results emphasize the need for research relating behaviour and morphology to environmental conditions. As moose are well adapted to snow and winter conditions, climate change may have negative consequences on southern populations as temperatures will rise, and some ranges may become unsuitable