Physiological and ecological aspects of winter torpor in captive and free-ranging striped skunks.

摘要

The principle objective of this investigation was to develop an understanding of the physiological response and ecological aspects of winter torpor of small carnivores, specifically striped skunks (Mephitis mephitis) in the northern environment. An experiment was undertaken to investigate the physiological response of skunks to solitary and communal over-winter strategies. Solitary skunks were able to undergo daily torpor to conserve energy to survive the winter, whereas communal skunks were able to use social huddling to reduce energy expenditure and rarely entered torpor. Due to seasonal changes in life requirements, den selection criteria change throughout the year. I examined the landscape metrics and habitat characteristics surrounding dens to evaluate the hierarchical selection and use of dens during winter (i.e., for torpor) and summer (i.e., for parturition). Den structures commonly used for winter dens were buildings, whereas den structures used for maternity dens were rockpiles and underground burrows. Habitat surrounding den sites influenced den use, animals chose den sites closer to roads, water sources, habitat edges, and crop fields. Seasonal movements of skunks from winter dens to the following summer home ranges were examined with respect to winter grouping (i.e., solitary or communal) and winter den structure (i.e., underground burrow or building) to investigate factors that influence spatial distribution of skunks. Male and female skunks moved similar distances (∼1.5 km) from winter dens to the center of home ranges established in summer, irrespective of winter grouping status and winter den structure use. Due to limited movement in spring, skunks from communal winter dens had higher spatial overlap of summer home ranges than did skunks from solitary dens, producing spatial aggregation of skunk activities surrounding winter communal den sites. Consequently, winter communal dens represent localized "hotspots" in the landscape. The effects of extrinsic variables (i.e., environment and diseases) and intrinsic characteristics (i.e., age, gender, and body condition) on cumulative winter survival rate were examined. Winter survival rates were driven mostly by winter condition (i.e., low ambient temperature and snow depth), rabies, and body condition. These results suggest that winter severity probably poses a limit on the northern distribution of the species.