We observed carcasses and bear tracks on survey routes that were travelled biweekly during spring of 1985-90 in the Firehole-Gibbon winter range and spring of 1987-90 in the Northern winter range. Most kills known to occur on land (Stirling and Ross 2011 Ivanov et al.We studied the spring use of ungulate carcasses by grizzly bears (Ursus arctos horribilis) on ungulate winter ranges in Yellowstone National Park.For males, to increase breeding opportunities (infanticide).Possible motivations (see refs in Stirling and Ross 2011 Ivanov et al.May be killed in a similar manner to how polar bears hunt seals (bites behind the head).Bears at risk are mainly cubs, but sometimes also adult females (Stirling and Ross 2011).Thought to occur infrequently (Stirling and Ross 2011).Fewer scavengers on sea ice than land behavior may benefit polar bears less than other bear species.Observed in Svalbard, Greenland, and Canada.Short-term generally cache for only a few days.After eating prey's fat and other high-value tissues, may bury carcass under snow, grass, or dirt.Provides little opportunity for weight gain/maintenance (Pagano et al.Scavenge more commonly than adults, which are more adept and experienced hunters.Subadults may scavenge kills left by larger individuals (e.g., Stirling 1974 Pilford et al.Wash and lick themselves while feeding spend up to 15 minutes grooming afterward.But bears may scavenge together at a whale carcass or human garbage dump.Small size of prey probably eliminates any advantage in group hunting.Considerable competition between Polar Bears for a kill larger bears will run off smaller bears.Large adult males may be better able to hunt larger prey (e.g., large seals, beluga, etc.).Prey selection may differ somewhat between male and female polar bears (Galicia et al.Swim underwater to stalk seals lying at the edge of an ice floe.May break into lair immediately, or wait motionless and listening for several hours for seal to return.Approach slowly to minimize their own sound.Locate birth lairs and breathing holes of Ringed Seals by smell and sound.Use sit-and-wait tactics to hunt seals (e.g., Pagano et al.Sodium content is higher than that of other milks. ![]() 35.8% milk fat when emerge from dens - 20.6% fat with yearlings.Polar Bears have richest milk of all bears.Bear milk is high in fat and protein but low in carbohydrates.Phosphate, lipid and cholesterol contents relatively low.Vitamin A content of liver ranges between 15,000 and 30,000 units per gram.Water released when fat is digested (metabolized).Large stomach can hold more than 70 kg (154 lb) of food.Can endure long periods without feeding (e.g., Pilford et al.Metabolize fat when there is nothing to eat.Gain majority of their body fat in the late spring and early summer.Consume large amounts of fat when food is available.High energy (metabolic) needs (Pagano et al.Arctic fox, wolf, muskox, Willow Ptarmigan, gulls.In Nunavut, Canada: infrequently scavenge remains of land mammals and birds (Michaux et al.One hunting event involved a polar bear chasing and overtaking a reindeer in water.Since 2000, observed hunting reindeer in Svalbard, Norway (Iversen et al.E.g., bowhead whale remains in Northern and Southern Beaufort Sea, and Foxe Basin, Canada.2022) and killer whale predation (Galicia et al. Opportunistically feed on whale carcasses caught by native subsistence hunters (Rogers et al.In summer, if preferred food is unavailable, take land plants and lichen, seaweed/kelp, berries, small mammals, birds, and egg ((Lønø 1970 Iversen et al.Geese, eider, and other seabirds and waterfowl (Stempniewicz 2006 Prop et al.Foraging on seal carcasses, at bowhead bone piles (discards of native subsistence hunting), and from human trash.In recent years, observations of polar bears in Alaska broadening somewhat diet to include harder foods (Petherick et al.(2013) noted polar bear's diet can shift to include more subarctic seal species with warmer temperatures and less sea ice Smaller grinding surfaces on molars compared to brown bears.Skull and teeth not well adapted for processing bone and tough plant foods. ![]() Diet constrained by skull morphology (Slater et al.Primarily carnivorous, compared to brown and black bears (Rinker et al.Polar bears are adapted to eat soft, high-calorie skin and blubber (also, flesh but often leave meat for scavengers). ![]()
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