Similar Winter Energy Strategies of Grouse, Hares and Rabbits in Northern Biomes

Neutral fat and protein reserves were measured in three species of grouse, cottontail rabbits, snowshoe hares and European hares collected during the mid to late winter period in their natural habitats. Neutral fat levels were measured in arctic hares from the Canadian high arctic during late summer. Sharp-tailed grouse, spruce grouse and ruffed grouse contained, respectively, 2.2, 2.3 and 1.0 g of fat per 100 g fat-free body weight, regardless of sex, year or location. Cottontail rabbits, arctic hares, snowshoe hares and European hares had, respectively, 4.1, 2.5, 2.3-4.1 and 6.9 g of fat per 100 g fat-free body weight. The low values for fat and protein reserves are similar to those reported for other grouse and leporid species in different parts of North America and Scandinavia. Collectively they indicate that species in both taxa have little metabolic resistance to winter fasting and must feed regularly to maintain energy balance. Grouse, hares and rabbits in winter habitats share similar energetic tactics of acquiring small energy reserves, feeding regularly for short periods and emphasize energy conservation rather than energy acquisition. A theoretical model relates the size of energy reserves in these species to the probability and duration of fasts due to severe winter weather, the changing quality of diets, and the probability of predation while amassing reserves prior to winter and using them during winter.