After eating all the deer on the island, the wolf (Canis lupus) on a remote island in Alaska, USA, began to hunt sea otters (Enhydralutris) as their main food source.
The event took place on Pleasant Island, 65 kilometers west of Juneau, Alaska, and was the first time that sea otters were found to be the main source of food for land predators.
In 2013, the wolves crossed the water, causing the deer population on Pleasant Island to plummet.
However, the wolves did not leave after eating all the deer on the island. Scientists have been tracking the lives of wolves since 2015 and have seen how they switch to eating sea otters.
Gretchen Roffler, a wildlife scientist at the Alaska Department of Fish and Hunt, said: "The wolves not only eat the sea otters that have died or died, but they also stalk and hunt healthy sea sloths and then drag them out of the water and eat them." ”
To study the wolves' eating habits, researchers put GPS collars on some of the wolves and collected 689 fecal samples, most of which were scattered along the island's coastline.
DNA analysis can determine which wolf a portion of feces came from and what it ate. According to statistics, between 2015 and 2020, the proportion of deer in the diet of wolves decreased from 75% to 7%.
At the same time, sea otters make up 57 percent of the wolf pack's diet, up from 25 percent.
The data on the GPS collar also confirmed that the wolves did not leave Pleasant Island to hunt elsewhere. When the wolves are on the move, they will crouch on the shore before catching unsuspecting sea otters from the shallow waters, or ambushing them resting on the rocks at low tide.
"What strikes me most incredible is that the sea otters have become the main source of food for the wolves on this island," Loefler said. It's not a big deal for wolves to eat an occasional sea otter that has washed up on the beach to rest.
But when wolves often hunt sea otters, it is a sign that eating sea sloths has become a common behavior in the pack and that members of the pack can quickly learn how to hunt sea otters. ”