HUDDLING BEHAVIOR AND THE FORAGING EFFICIENCY OF MUSKRATS

The potential benefits of social aggregation and communal grooming to the foraging ecology of muskrats were investigated. We hypothesized th at muskrats in groups would be more resistant to hypothermia, would sp end more time foraging in cold water, and would rewarm more quickly fo llowing emergence than solitary muskrats. Despite social grooming and aggregation behavior following episodes of aquatic activity, the post- immersion rewarming rates of muskrats increased only slightly in the p resence of nestmates. The maximum rate of rewarming averaged 0.26 degr ees C/min when each animal was tested alone, and 0.30 degrees C/min wh en it was tested in the presence of four nest-mates (P = 0.096). Provi ding muskrats with the option to huddle between foraging and explorato ry dives in cold water had little impact on the precision of control o f body temperature. Although muskrats in groups tended to spend more t ime in water and expend less energy than solitary animals, these trend s were not significant. The greatest-differences were in intake of foo d, with grouped animals in one experiment ingesting nearly three times as much forage as animals feeding alone (P = 0.015). We attribute the higher intake of food of grouped animals to social facilitation rathe r than to any gain in foraging efficiency arising from aggregation beh avior out of water.