On Prince of Wales Island, Alaska, gray wolves are showing an unusual behavior: they are hunting sea otters. This unexpected shift in diet could have wide-ranging effects on coastal ecosystems and on the wolves themselves. However, scientists still know very little about how these predators manage to catch prey in a marine environment. Patrick Bailey, a Ph.D. candidate at the University of Rhode Island, is leading research into these little-studied behaviors.
Using a creative mix of approaches -- including wolf teeth samples and trail cameras -- Bailey is examining how coastal gray wolves rely on marine food sources, what this reveals about their hunting strategies, and how these wolves differ from inland populations.
Linking Land and Ocean Ecosystems
Gray wolves are well known for their powerful influence on land-based food webs, where they help regulate prey populations and shape ecosystems. Bailey believes similar connections may exist between terrestrial and aquatic environments. "We don't have a clear understanding of the connections between water and land food webs, but we suspect that they are much more prevalent than previously understood," says Bailey, who works in Sarah Kienle's CEAL Lab in the Department of Natural Resources Science. "Since wolves can alter land ecosystems so dramatically, it is possible that we will see similar patterns in aquatic habitats."
Teeth Tell the Tale
Sea otters, now classified as an endangered species, once thrived along the Pacific Coast before the fur trade during westward colonial expansion drastically reduced their numbers. As sea otter populations slowly recover, wolves may be reviving a predator-prey relationship that existed in the past. Researchers are now trying to determine how this interaction affects wolf behavior and whether it influences sea otter recovery.
To investigate these questions, Bailey is analyzing gray wolf teeth from museum collections and recently deceased animals using stable-isotope techniques. Like tree rings, teeth grow in layers that record changes over time. "If large enough, we can individually sample each of these growth rings to track an individual's feeding patterns over time," he explains. "When we gather enough samples across individuals we can then analyze how prevalent these dietary trends are throughout a population."
Kienle notes that hunting in the ocean presents very different challenges than hunting on land. "Capturing and eating prey in the marine environment is very different from doing it on land," she says. "We are super curious to see if these coastal wolves have behavioral adaptations that are different from terrestrial wolves."
Although there have been official reports of wolves eating aquatic prey for more than 20 years, many details remain unknown. "What hasn't been explored, and what I am really interested in documenting, is how exactly wolves are able to capture sea otters," Bailey says.
New Technology Brings Fresh Insight
Earlier video footage of wolf hunts lacked the clarity needed for close study, but newly installed trail cameras may finally provide answers. These cameras were set up by Bailey on the island during the summer and are positioned to capture more detailed behavior. "So far, we know that these wolves are consuming sea otters," he says, "and we're now staged to capture the details that have previously eluded us." A team of seven University of Rhode Island students has been trained to help review more than 250,000 images of wolves and sea otters collected since last December.
Studying wolves in such conditions is no easy task. Bailey points out that their intelligence and elusive nature make them difficult subjects, especially in a remote landscape. "When you pair these traits with a landscape that is very rural and difficult to traverse, researching them becomes quite the undertaking," he says.
Prince of Wales Island was chosen as the main field site through a partnership with Alaska Department of Fish and Game biologist Gretchen Roffler and local research technician Michael Kampnich. Bailey emphasizes their role in the project's success. "I cannot emphasize enough how much these two have helped me," he says. "This project would not be possible without their input and guidance."
Kampnich, in particular, has helped the research team understand the island's ecology and terrain. "Kampnich has been an unbelievable resource for getting us acquainted with the island and its unique ecology," Bailey adds. "Working with locals is so important because they have decades of experience and perspective that we as outside researchers simply do not have."
Mercury Risks Move Up the Food Chain
Roffler's recent findings raise concerns about another consequence of marine hunting. Her research shows that sea otters can accumulate high levels of methylmercury, a toxic form of mercury. This raises the possibility that wolves feeding on otters may also be exposed. Liver samples from coastal gray wolves show mercury concentrations far higher than those found in inland wolves -- up to 278 times greater -- which could pose serious long-term health risks. "Methylmercury accumulation can cause a suite of problems related to reproduction, body condition, and behavioral abnormalities," Bailey explains.
Expanding the Research Eastward
Although the current focus is on Alaska, Bailey hopes to broaden his research in the future. Limited resources mean his work is centered on areas where data collection is most promising, but he plans to include the east coast as well.
"I'm including historical east coast wolves in a separate chapter of my dissertation comparing skull morphology between coastal and inland populations," he says. He is currently studying skull specimens from parts of Canada, including Newfoundland and Labrador, provided by the Harvard Museum of Comparative Zoology.
For now, data collection continues, with research expected to span several more years. Bailey also plans to return to Prince of Wales Island next summer to continue fieldwork.
