Gray Wolves Are Hunting Sea Otters – and Scientists Don’t Know How

New research broadens our understanding of how gray wolves interact with and influence aquatic habitats.

On Prince of Wales Island, Alaska, gray wolves have been observed engaging in an unusual behavior: preying on sea otters. This unexpected shift toward marine prey could have important consequences for both coastal ecosystems and the health of the wolves themselves.

Despite its potential significance, little is known about how wolves manage to capture animals in the ocean. Patrick Bailey, a Ph.D. candidate at the University of Rhode Island, is investigating these little-studied aspects of gray wolf behavior.

By combining several innovative methods — including analysis of wolf teeth and the use of trail cameras — Bailey is examining how coastal wolves rely on marine food sources. His work aims to clarify what this reliance reveals about their hunting strategies and behavioral flexibility, as well as how these coastal wolves differ from inland populations.

Gray wolves are well known for their influence on terrestrial ecosystems through their ability to shape food webs.

“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 listed as an endangered species, were once widespread along the Pacific Coast before the fur trade during westward colonial expansion drastically reduced their numbers. As sea otter populations continue to recover, wolves may be reestablishing a predator-prey relationship that existed in the past. Scientists are now exploring whether this interaction influences wolf behavior and affects the long-term recovery of sea otters.

To better understand these dynamics, Bailey is conducting stable-isotope analysis on gray wolf teeth from museum collections and recently deceased wolves. Similar to tree rings, the wolves’ teeth contain layers of growth that reveal their dietary history. “If large enough, we can individually sample each of these growth rings to track an individual’s feeding patterns over time,” he says. “When we gather enough samples across individuals, we can then analyze how prevalent these dietary trends are throughout a population.”

“Capturing and eating prey in the marine environment is very different from doing it on land,” adds Kienle. “We are super curious to see if these coastal wolves have behavioral adaptations that are different from terrestrial wolves.”

While there are over two decades of official reports of wolves consuming aquatic prey, many questions remain. “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 tech, new clues

While the resolution of initial footage of wolf hunts was too low for detailed analysis, new trail cameras installed by Bailey on the Alaskan island this summer may finally capture the details of how wolves are hunting sea otters. “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.” Bailey has trained a team of seven URI students to help analyze more than 250,000 images of wolf and sea otter activity captured since last December.

One of the challenges of conducting this research has been the wolves themselves, Bailey notes. Highly intelligent and elusive, they are notoriously difficult to study. “When you pair these traits with a landscape that is very rural and difficult to traverse, researching them becomes quite the undertaking,” Bailey says.

Prince of Wales Island was selected as the primary research site for Bailey’s fieldwork thanks to a collaboration with Alaska Department of Fish and Game biologist Gretchen Roffler and Michael Kampnich, a research technician who is local to the area. “I cannot emphasize enough how much these two have helped me,” Bailey says. “This project would not be possible without their input and guidance.”

“Kampnich has been an unbelievable resource for getting us acquainted with the island and its unique ecology,” he adds. “Working with locals is so important because they have decades of experience and perspective that we as outside researchers simply do not have.”

Roffler’s recent research on high levels of methylmercury, a toxic form of mercury, accumulated in sea otters signals potential concerns for how gray wolves’ diets might move that mercury up the food chain. Liver samples from aquatic gray wolves reveal mercury levels significantly higher than their inland counterparts — up to 278 times greater — raising concerns about long-term health effects. “Methylmercury accumulation can cause a suite of problems related to reproduction, body condition, and behavioral abnormalities,” Bailey notes.

East Coast directions

While currently focused on Alaskan wolves because resources are allocated to areas that have the highest probability of capturing data, Bailey hopes to eventually expand the behavioral aspect of his research to include the East Coast.

“I’m including historical east coast wolves in a separate chapter of my dissertation comparing skull morphology between coastal and inland populations,” he notes. He’s currently working with skull specimens of wolves from regions of Canada, including Newfoundland and Labrador, shared with him by the Harvard Museum of Comparative Zoology.

In the meantime, his research is ongoing and data collection is expected to continue over the next several years. He hopes to return to Prince of Wales Island for additional fieldwork next summer.

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