In the summer of 2013, two Alexander Archipelago wolves (Canis lupus ligoni), a subspecies of gray wolf, swam across a narrow channel to reach Pleasant Island, Alaska, a 50 square kilometer (19 square mile) rock jutting out of the stormy Gulf of Alaska. Wolves hadn\u2019t previously lived on Pleasant Island, and they quickly ran roughshod over the island\u2019s deer population. Within a few years, the wolves blossomed to a family of 13, and the deer, in turn, were entirely wiped out.<\/p>\n
As the deer declined, Gretchen Roffler, a biologist with the Alaska Department of Fish and Game, wondered about the wolves\u2019 fate. Would they abandon the island and swim back to the mainland, some 3 kilometers (2 miles) away? Or would they stay and starve to death? As it turned out, they did neither. Instead, the wolves adapted to island life in an unexpected way<\/a>: They started eating sea otters.<\/p>\n \u2018\u2019They\u2019ve learned how to kill them,\u201d Roffler says. By collecting and analyzing samples of wolf fur and scat, Roffler and her colleagues showed that sea otters now constitute a very large part of their diet. \u201cFrom 60 to 70 percent,\u2019\u2019 she says. The remainder is made up of salmon and other fish, as well as birds, such as ducks and bald eagles. The occasional harbor seal and Steller sea lion also make the menu.\u00a0<\/p>\n In a rapidly changing world, predators adapting to new kinds of prey is, in many ways, a sign of adaptability and resilience. But unfortunately for Pleasant Island\u2019s wolf population, something dangerous was lurking in their new otter-heavy diet.<\/p>\n In 2020, one of Pleasant Island\u2019s wolves\u2014the pack\u2019s reproductive female\u2014suddenly stopped moving. Roffler and her colleagues headed out to investigate, tracking the signal from the wolf\u2019s GPS collar. They discovered the wolf\u2019s emaciated corpse lying beneath a tree. Keen to get to the bottom of her death, Roffler and her team analyzed the wolf\u2019s tissue. Their research revealed something unexpected: the highest level of the toxic heavy metal mercury ever recorded in a wolf.<\/p>\n