After swimming out from the mainland of Alaska’s panhandle in 2013, wolves established themselves on Pleasant Island and took an immediate liking to the island’s Sitka black-tail deer population. In the years that followed, wildlife officials watched as the deer population quickly dwindled in succession with the growth of the newly established pack of gray wolves.
It didn’t take long until the island was completely devoid of anything that resembled traditional table fare for the wolves and now researchers are finding that they have taken to sea otters, another local predator, as their main source of protein.
“No one would have predicted this,” says Taal Levi, a wildlife ecologist at Oregon State University.
It’s believed that this rare phenomenon in which land mammals are including sea otters as their primary food choice is a first not only in Alaska, but around the world.
As scientists watched the island’s wolves decimate the black-tail population, many expected that the wolves would simply pack up and move on – not unlike any other large predator without a main source of food. Instead, the wolves doubled-down and stayed on Pleasant Island and are now said to be thriving on their new found diet of fast-moving sea dwellers.
In an effort to understand the rare occurrence, researchers set up shop on the island in hopes of finding out exactly what the wolves were feeding on. While it was a general consensus that wolves would waste no time feasting on an injured or already deceased otter, many didn’t believe they were actively pursuing them.
A wolf drags a sea otter carcass. Alaska Department of Fish and Game.
Scatty Answers
To figure out what the animals were digesting, researchers turned to scat sample selection. During a period between 2015 to 2021, the team collected nearly 700 scat samples for analysis. The early collection data from 2015 indicated that deer made up about 75 percent of the wolves diet and the remaining 25% was made up of sea otters.
By 2017, everything had changed. By this point, island deer populations were in a downward spiral and scat sampling indicated that sea otters were now making up about 57 percent of the wolves’ diet. Deer declined to represent only 7 percent of their diet, the remaining being made up of a variety of other sea creatures.
Travel Time
Following the digestive analysis, researchers wanted to confirm that the wolves were not, in fact, traveling between the mainland like a group of drug mules, smuggling in full bellies of panhandle deer.
By affixing GPS collars to nine mainland wolves and an additional four Pleasant Island wolves, it was confirmed that the islanders were staying dry and not making the trek back and forth from the mainland. Further data went on to confirm that the consumption of sea otters by the island’s wolves was not purely opportunistic in nature. They were actively pursuing sea otters in shallow water or along rocky shorelines for most of their meals.
“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 said in the statement. “But … from the work we are doing investigating kill sites, we are learning that wolves are actively killing the sea otters.”
Meanwhile, Levi’s lab and their team continue to pursue the study of wolf and sea otter interactions, this time in Katmai National Park and Preserve. While the park is about 700 miles from Pleasant Island, early research indicates that wolves there are dining on sea otters as well.
