The nutritional ecology of small mammals

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We study the life histories of deer mice and voles in short-summer environments in southwestern Alberta, where age at maturation is often delayed to one year of age, survival of nestlings is variable, and survival of adults is high. These populations are vulnerable to disturbance because turn-over rates and recovery from declines are slow. Rates of metabolism are dictated by ambient temperatures and approach maximum sustainable as temperatures approach zero, constraining reproduction to a short summer season. There are no energetic constraints on reproduction during the summer. Our food supplementation studies have identified nutritional constraints on nestling growth, maturation, and the initiation of breeding in the spring but no effect on nestling or adult survival. Our current research investigates the demographic responses of deer mice and voles to changes in the quality of natural diets. Deer mice are omnivorous (mostly seeds and invertebrates, with invertebrates representing a high quality diet) and stable isotopes of nitrogen in hair samples are being used to identify seasonal and annual differences in their diet quality. Voles are mostly herbivorous and granivorous and the palatability of seeds and green vegetation (and the availability of plant species) are being used to identify seasonal and annual differences in their diet quality. Our future research will focus specifically on demographic and population responses of mice and voles to conifer seed production, the biochemistry of plant secondary compounds, the role of food storage in improving the quality of unpalatable plant species, and a comparison of diet quality among voles with different litter sizes.