After devouring their island’s deer, these canines may be the first land predators to rely on sea otters as a main food source.
Wolves on an Alaskan island have turned to hunting and eating sea otters as their main source of food, after decimating the local deer population. This might be the first case of these marine mammals becoming the primary food source for a land-based predator, per a statement.
“No one would have predicted this,” says Taal Levi, a wildlife ecologist at Oregon State University who participated in the research, to New Scientist’s Clare Wilson.
Typically, wolves rely on hoofed mammals, such as deer, for food. But the new findings, published Monday in Proceedings of the National Academy of Sciences, suggest that doesn’t have to be the case.
“This is pretty phenomenal that one predator is basically living off of another predator in a different system,” Layne Adams, a wildlife biologist at the U.S. Geological Survey who wasn’t involved in the study, tells Science’s Jack Tamisiea.
Wolves swam from mainland Alaska to establish a population on Pleasant Island in 2013. In just a few years, they consumed most of the island’s Sitka black-tailed deer. Without a large herbivore to feed on, scientists expected the canines to leave the island or die off. But instead, they stayed and thrived.
To figure out why, researchers studied wolves on Pleasant Island and the nearby mainland from 2015 to 2021, collecting a total of 689 scat samples. They found that in 2015, deer made up about three-quarters of the wolves’ diet, and sea otters made up the other quarter. But by 2017, this had shifted: Sea otters represented about 57 percent of the wolves’ diet, while deer declined to only 7 percent. Other sea creatures made up much of the rest of the wolves’ meals.
Researchers also attached GPS collars to nine wolves from the mainland and four from Pleasant Island to determine whether the animals were traveling between those locations and where they were feeding. They discovered that the island wolves stayed put—and that they were killing sea otters in shallow water or while the animals were resting on rocks near the shore.
“Occasionally eating a sea otter that has washed up on the beach because it died, that is not unusual,” Gretchen Roffler, a wildlife research biologist with the Alaska Department of Fish and Game and the study’s first author, says in the statement. “But … from the work we are doing investigating kill sites, we are learning that wolves are actively killing the sea otters.”
Populations of sea otters in the region declined in the 1800s and much of the 1900s because of the fur trade, but in recent decades, otter reintroduction and legal protections have helped boost their numbers. Now, even the mainland wolves seem to be feeding on the creatures—perhaps reviving an ancient relationship between the two species, per Science.
“The reintroduction of sea otters is restoring this interaction between the sea and the land that has existed forever,” Levi tells the publication.
Source: Smith Sonian Mag