Ursus maritimus

Abstract

Ursus maritimus Phipps, 1774 Polar bear Ursus maritimus Phipps, 1774:185. Type locality Spitzbergen. Ursus marinus Pallas, 1776:691. Type locality Arctic Ocean, Siberia. Ursus polaris Shaw, 1792:7. Renaming of marinus Pallas. Thallassarctos eogroenlandicus Knotterus-Meyer, 1908:182. Type locality pack ice off coast of eastern Greenland. Th[alassarctos] labradorensis Knotterus-Meyer, 1908:183. Type locality Okak, Labrador. ?Thalassarctos jenaensis Knotterus-Meyer, 1908:184. Type locality Jena Island, Spitzbergen. ?Th[allassarctos] spitzbergensis Knotterus-Meyer, 1908:184. Type locality Seven Islands, Spitzbergen. CONTEXT AND CONTENT. Order Carnivora, Family Ursidae. The genus Ursus includes three species. The living populations of Ursus maritimus are not divided into subspecies (Wilson, 1976), although one fossil subspecies is recognized (Kurten, 1964). DIAGNOSIS. Typically the body of a polar bear is stocky but lacks a shoulder hump. Polar bears have a longer neck and smaller head than other ursids (Fig. 1). The combined length of the first and second molars is less than the palatal width. GENERAL CHARACTERS. Fur color varies among white, yellow, grey, or almost brown, depending on season and light conditions. The nose and lips are black, as is the skin. Adult males weigh 300 to 800 kg and measure 200 to 250 cm in length from tip of nose to tip of tail. Adult females weigh 150 to 300 kg and their total body length is about 180 to 200 cm. It is not meaningful to give mean weights because there is a dine in size from Spitzbergen, where the bears are smallest, to the Bering Strait where they are largest (Manning, 1971). Presumably the dine is similar across the Soviet Arctic to the Bering Strait, but this has not been investigated. Cubs weigh roughly 0.6 kg at birth and 10 to 15 kg when they emerge from dens in March or April. In March, yearlings weigh between 45 and 80 kg, while 2-year-olds weigh between 70 and 140 kg. Females reach adult weight by year 5 and males between years 8 and 10. The length of skull (Fig. 2) ranges from 353 to 412 mm in males and from 311 to 380 mm in females. For adults, the height at the shoulder varies from about 130 to 160 cm. The length of tail ranges between 76 and 127 mm (Uspenskii, 1977). Polar bears have a plantigrade gait and five toes on each foot. The claws are not retractable and in adults are 5 to 7 cm in length. The forepaws are large and oarlike, as an adaptation for swimming. DISTRIBUTION. Polar bears are circumpolar in distribution. The southern limits of their range are determined by the distribution of pack ice and annual landfast ice during winter (Fig. 3). The centers of six apparently distinct populations in the main polar basin are: Wrangel Island and western Alaska, northern Alaska, the Canadian Arctic archipelago, Greenland, Svalbard- Franz Josef Land, and Central Siberia (Parovschikov, 1964, 1968; Uspenskii, 1965; and Vibe, 1967; Lentfer, 1974a; Stirling et al., 1975; Jonkel et al., 1976). Discrete subpopulations exist within the Canadian Arctic archipelago and James and Hudson bays (Stirling et al., 1975, 1977, 1978, in press). Polar bears have been recorded as far as 88?N (Stefansson, 1913, 1921) and as far south as St. Mathew Island and the Pribilof Islands (Ray, 1971)