THERMAL BENEFITS OF HUDDLING IN THE MUSKRAT (ONDATRA-ZIBETHICUS)

We examined the energy saving and social interactions associated with winter huddling behavior in the muskrat, Ondatra zibethicus. At air temperatures of -10-degrees-C and 0-degrees-C, which encompass the lowest microclimate temperatures recorded from winter shelters, the resting metabolic rate of an aggregate of four muskrats averaged 11-14% below that of single animals. The minimal thermal conductance of the grouped animals was reduced by 8-10% over this same temperature range. Our findings suggest that communal nesting confers a modest, but potentially significant metabolic saving to overwintering muskrats.