area. The melting sea ice in the Arctic may be causing an increase of orcas in the Arctic sea, which may increase the risk of predation on polar bears but also may benefit the bears by providing more whale carcasses that they can scavenge. The remains of polar bears have been found in the stomachs of large Greenland sharks (Somniosus microcephalus), although it certainly cannot be ruled out that the bears were merely scavenged by this slow-moving, unusual shark. A rather unlikely killer of a grown polar bear has reportedly included a wolverine (Gulo gulo), anecdotally reported to have suffocated a bear in a zoo with a bite to the throat during a conflict. This report may well be dubious, however. Polar bears are sometimes the host of arctic mites such as Alaskozetes antarcticus. Long-distance swimming and diving Researchers tracked 52 sows in the southern Beaufort Sea off Alaska with GPS system collars; no boars were involved in the study due to males' necks being too thick for the GPS-equipped collars. Fifty long-distance swims were recorded; the longest at , with an average of . The length of these swims ranged from most of a day to ten days. Ten of the sows had a cub swim with them and after a year, six cubs survived. The study did not determine if the others lost their cubs before, during, or some time after their long swims. Researchers do not know whether or not this is a new behaviour; before polar ice shrinkage, they opined that there was probably neither the need nor opportunity to swim such long distances. As noted above, there have been 600 recorded instances of polar bears in Iceland since the 9th century. These presumably swam from Greenland, about . The polar bear may swim underwater for up to three minutes to approach seals on shore or on ice floes. Hunting Indigenous people Polar bears have long provided important raw materials for Arctic peoples, including the Inuit, Yupik, Chukchi, Nenets, Russian Pomors and others. Hunters commonly used teams of dogs to distract the bear, allowing the hunter to spear the bear or shoot it with arrows at closer range. Almost all parts of captured animals had a use. The fur was used in particular to make trousers and, by the Nenets, to make galoshes-like outer footwear called ; the meat is edible, despite some risk of trichinosis;