People love otters, wolves and deer. Each one is cunning, intelligent, and dignified. However, when you put them all together on an island, things quickly get nasty. A new paper finds out how they used food sources to thrive to the point of wiping out native Sitka white-tailed deer populations.
“To the best of our knowledge, deer populations have plummeted. We have found no evidence that deer have repopulated the islands,” said the study’s author, a wildlife research biologist with the Alaska Fish and Game Service. One Gretchen Loefler told Ars.
deer diary
Deer have been on Pleasant Island for a long time. Sea otters also lived in waters off Alaska until the fur trade mostly wiped them out in the late 1800s and early 1900s, Loeffler said. However, sea otters were listed as an endangered species and populations were reintroduced to the area in the 1960s. In the 1980s, they migrated to the waters near Pleasant Island and continued to breed.
The wolf lived in southeastern Alaska and made an odd sojourn on Pleasant Island, though it didn’t stay long. Since 2013, however, wolves have been available full-time. Loeffler said they likely crossed about a mile of water from the mainland to get there.
Loeffler and her team wanted to document predator-prey interactions between wolves and deer on the island. The researchers initially thought the wolves either migrated by eating deer or starved to death. However, the presence of sea otters belied these expectations.
otter watch out
The team studied the island’s wolves, tested DNA found in 689 wolf poop, and performed stable isotope analysis of hair and muscle material obtained from local hunters. The team tracked the wolf from 2015 to 2021.
Samples taken from the wolves contained otter and deer DNA, indicating a diet switch from Sitka black-tailed deer (the main prey wolves typically ate) to sea otters. The paper notes that this is an “unintended consequence” of sea otter reintroduction and recovery. Sea otters have become “rich marine subsidies for wolves,” the paper said.
From the samples, the researchers confirmed that a diet that was primarily composed of deer changed to one that was primarily composed of sea otters. The study also found that additional, unexpected food sources allowed wolves to reproduce even after deer populations declined. Ultimately, wolves killed off the island’s deer population.
