Male Atlantic walrus weigh an average of . The island was also a habitat for the Atlantic walrus until the mid-16th century. North Ronaldsay was also a habitat for the Atlantic walrus through the mid-16th century. Larger species include Atlantic walrus, narwhal and sometimes beluga whale. The Atlantic walrus also tends to have relatively shorter tusks and somewhat more flattened snout. Atlantic walrus ("O. rosmarus rosmarus") have also been charted as far west as McDougall Sound.