ACTIVITY PATTERNS, FORAGING ECOLOGY, AND SUMMER RANGE CARRYING CAPACITY OF MOOSE (ALCES ALCES SHIRASI) IN ROCKY MOUNTAIN NATIONAL PARK, COLORADO
Keywords:activity patterns, Alces alces, behavior, carrying capacity, consumption, energy, foraging, moose, summer
To ensure sustainable populations of native animals and plants, managers of protected areas must understand carrying capacity of large wild herbivores. Estimates of carrying capacity and how large herbivores may influence native vegetation require knowledge of their activity and foraging patterns. Therefore, we examined activity patterns and foraging behavior of adult male moose (Alces alces shirasi) in Rocky Mountain National Park, Colorado by following individual animals and counting bites during the summer and fall of 2003 and 2004. Mean active time per day peaked in late June at 11.3 h and declined to 8.9 h in early fall preceding the breeding season. Moose averaged 6.7 feeding periods/d, each lasting 79 min; feeding bouts were longer around sunrise and sunset and were shorter midday presumably because of high ambient temperature. Activities associated with feeding and resting constituted 94.0% of daily time budgets. Feeding declined and social behavior and movement increased in fall with the onset of the breeding season. Food consumption increased steadily through early summer peaking at 126.8 g/kg BW0.75 in early August, followed by a sharp decline to a low of 69.1 g/kg BW0.75 in early September. Daily digestible energy intake was estimated at 1191 kJ/kg BW0.75/d. Maximum rates of instantaneous intake were recorded in early August at 22.3 g/min. Because intake rates of willow (Salix spp.) increased from June-August, but nutritional quality peaked in mid-June, increases in daily and instantaneous intake rates during summer seemed more related to forage availability than protein and energy content of willow leaves. The nutritional carrying capacity of summer range in Rocky Mountain National Park in 2004 was estimated from the range supply of metabolizable energy, digestible energy, and available nitrogen. Based on the digestible energy intake and energy requirements of a 344 kg male moose, the summer range carrying capacity was estimated at 0.21 moose/km2. Nitrogen based estimates were considerably higher at 0.32 moose/km2.
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