Scientists have reported that trampling by other walruses in a stampede likely caused the deaths of 131 walruses found on a beach in Alaska’s North Slope in August. Attributing a reduction in available sea ice to global warming, the scientists hypothesize that extraordinary numbers of walruses had crowded onto the shoreline, then stampeded when they were alarmed. Walruses routinely come ashore but over the past two years exceptionally large herds have been observed, with previous mass casualties from stampeding only being observed on the Russian side of the Chukchi Sea.
According to the preliminary report released by the US Fish and Wildlife Service, necropsies of 71 carcasses revealed mostly young animals with extensive bruising in the muscles of the neck and chest. Walrus calves weigh only 100-160 pounds and are vulnerable to trampling by heavier adults if startled by disturbances such as hunters, predators or planes. Since walruses cannot swim continuously, they depend on sea ice platforms for breeding, nursing, resting and foraging. The discovery of the dead animals and the growing threats to walruses from climate change, as well as from increasing oil exploration, has prompted the Service to consider listing the Pacific walrus as either threatened or endangered under the Endangered Species Act.