Arctic hare
The Arctic hare[2] (Lepus arcticus) is a species of hare highly adapted to living in the Arctic tundra and other icy biomes. The Arctic hare survives with shortened ears and limbs, a small nose, fat that makes up close to 20% of its body, and a thick coat of fur. It usually digs holes in the ground or under the snow to keep warm and to sleep. Arctic hares look like rabbits but have shorter ears, are taller when standing, and, unlike rabbits, can thrive in extreme cold. They can travel together with many other hares, sometimes huddling with dozens or more, but are usually found alone, sometimes taking more than one partner. The Arctic hare can run up to 60 kilometres per hour (40 mph).[3]
Description
The Arctic hare is one of the largest living lagomorphs. Typically, this species measures from 43 to 70 cm (17 to 28 in) long, not counting a tail length of 4.5 to 10 cm (1.8 to 3.9 in). The body mass of this species is typically between 2.5–5.5 kg (6–12 lb), though large individuals can weigh up to 7 kg (15 lb).[4]
Distribution and habitat
The Arctic hare is distributed over the northernmost regions of Greenland, the Canadian Arctic islands and Northern Canada, including Ellesmere Island, and farther south in Labrador and Newfoundland.[5] The Arctic hare is well adapted to conditions found in the tundras, plateaus, and treeless coasts of this region, including cold weather and frozen precipitation. The Arctic hare may be found at elevations from sea level to 900 m (3,000 ft).[5][6]
In Newfoundland and Southern Labrador, the Arctic hare changes its coat color, moulting and growing new fur, from brown or grey in the summer to white in the winter. This seasonal moulting also enables other Arctic animals, including ermine and ptarmigan, to remain camouflaged as the environment changes.[7] However, the Arctic hares in the far north of Canada, where summer is very short, remain white all year round.[7]
Feeding
The Arctic hare is a herbivore, specifically a folivore.[8] Arctic hares feed primarily on woody plants, with arctic willow constituting 95% of their diet year-round.[8] Arctic hares predominantly consume saxifrage, crowberry, and dwarf willow, but can also eat a variety of other foods, including lichens and mosses, blooms, other species' leaves, twigs, and roots, mountain sorrel and macroalgae (seaweed).[8][9] Arctic hare diets are more diverse in summer.[10] Although previously believed to still be primarily willow, dryas, and grasses, recent studies show that their diet becomes dominated by legumes, constituting 70% of their diet in the summer.[8][10] Arctic hares have been reported to occasionally eat meat, including fish and the stomach contents of eviscerated caribou.[8] They eat snow to get water.[8]
Physiology
The Arctic hare has many physiological features that are adaptive to its extreme environment. Despite a 17% - 38% lower than expected basal metabolic rate, the Arctic hare is able to maintain a body temperature comparable to other lagomorphs (38.9 degrees C) because of its low surface area to volume ratio and high insulation.[11][9][12] The lowered metabolic rate also allows the Arctic hare to save energy, making it adaptive for its cold and barren habitat.[11][9][12] In addition, the Arctic hare has high locomotive efficiency combined with long periods of resting and shorter bouts of foraging which enables it to conserve energy and survive on its low diet intake.[13]
The white fur of Arctic hares, in addition to their camouflage benefits in the winter, have a high reflectance which may prevent excessive heat gain during the day.[9][12] Behaviorally, the Arctic hare keeps warm in winter using body orientation, posture, and seeking or digging shelter.[14] When resting, Arctic hares maintain a nearly spherical shape and typically stay in groups, but do not huddle.[14] If the rabbits are solitary, they often rest in the shelter of large rocks protecting them from the wind and staying out of sight of predators.[14][9][13][12] In addition to rocks, Arctic hares also find shelter in other natural shelters such as snowdrifts, man-made structures, and even digging their own burrows in snowdrifts up to 188 cm in length.[14]
The body size of Arctic hares is often significantly less in the winter compared to the summer, likely caused by decreased food quality and availability in addition to a decreased metabolic rate.[9][12] Arctic hare body mass might also be affected by ambient temperature. At lower latitudes it was found that Arctic hares in Greenland exhibited larger body size with increased temperature, possibly caused by increased energy availability to contribute to body size and increased food plant availability.[15] The opposite is true at higher latitudes in which Arctic hares had smaller body sizes with increased temperature.[15] This trend is again linked to food plant availability.[15] In this case, decreased precipitation and increased temperatures in the higher latitudes of Greenland result in a lower food plant availability to contribute to body mass.[15]
There are four subspecies of this hare: