Glacier Bay National Park in Alaska is home to more than twice as many northern sea otters (Enhydra lutris kenyoni) as all of California is to southern sea otters (Enhydra lutris nereis). Studying the thriving northern species may hold important clues for the future of the recovering southern species. In August, Monterey Bay Aquarium researcher Jessica Fujii spent two weeks studying the Glacier Bay population in the wild.
Jess is a senior research biologist with the Aquarium’s Sea Otter Program. She studies both wild sea otters and pups raised by surrogate otters so they can be returned to the wild—as was the case with two juvenile males earlier this month.
“Mostly I’m looking at sea otter behavior and foraging ecology—what they’re eating and what that may tell us about the rest of the ecosystem,” Jess says. “It involves a lot of going out in the field and watching the otters from shore.”
This summer, she worked aboard the Alaskan Gyre, a 50-foot U.S. Geological Survey vessel.
“It looks like a fishing boat, but it’s been converted for research purposes,” she says. “What used to be the fish hold is now sleeping quarters and storage.” With six or seven others aboard, “it was cozy; there’s not a lot of extra space.”
The trip was part of a longstanding collaboration between the Aquarium and researchers with the USGS Alaska Science Center. The two groups sometimes share insights and help each other observe or capture sea otters: “Having that crossover can be really helpful,” Jess says. “It’s also a way to make sure we’re maintaining comparable methods.”
Those methods can involve working 10- to 12-hour days in the rain while keeping an eye out for bears.
A day in the life
To get to shore, Jess and a partner would set out in a small skiff or inflatable each morning around 8 o’clock. They’d bring with them a telescope and tripod to observe the otters, as well as day packs with food and layers of clothing, including rain gear.
Also bear spray.
“Even when you’re on a small island, there’s the potential for bears to be around. You go through training of what to do if you see a bear, but mostly we were just trying to avoid any encounters,” she says.
(Although Jess saw a black bear with three cubs, “once she caught our scent she just turned and decided to go inland.” Phew.)
Because sea otters bring whatever food they find to the surface, scientists like Jess can watch them to get a sense of the nearby dining options.
“If there are multiple otters around, you’re trying to keep track of one individual, so that can be a challenge. You want one you can identify based on fur coloring or a distinct mark on their nose. We would try to record 20 dives on a single individual,” and repeat that process over and over throughout the day, she says. They observed males and females, young and old, and mothers with pups—all of which might forage differently.
One twist scientists are examining: most of the otters were eating tiny mussels, maybe an inch long.
“That’s really small for an otter,” she explains. “We typically expect that they would selectively go after larger prey—that’s kind of a bigger bang for the buck. They were basically tossing them into their mouths without any manipulation or breaking open the shells first—almost like popcorn.”
In Glacier Bay about eight years ago, Jess saw otters eating much larger clams and horse mussels. A potential explanation for the shift is that such food is no longer around, and the otters are adjusting their diet.
Of populations and pups
Jess is careful to note the many differences between Glacier Bay—a soft-sediment habitat—and the kelp forests of California’s rocky shore. California’s coastline is fairly linear (sea otters can travel north or south, and that’s about all). In southeast Alaska, the jagged tangle of inlets lets them “move in pretty much every direction.” Otters in California have the support of more ecotourism; the list goes on.
With an estimated 8,000 sea otters in Glacier Bay alone, and many more throughout Alaska (compared to around 3,000 in all of California), Jess could easily stand on a spit of land and see zero other humans—and hundreds of otters.
“When I was there, one location had a raft of probably 400 otters,” she says. “We don’t see groups that large in California. A large raft in California is 50, 60 otters.”
And in contrast with Monterey’s steady wave action, Glacier Bay was much calmer, making it much easier to hear sea otters vocalize.
“Most people don’t realize how noisy otters can be,” Jess says. “They can actually be pretty talkative.” Often, this involves a conversation between high-pitched pups and their foraging moms. (“They kind of coo.”) It can, she says, resemble a game of Marco Polo.
“Multiply that by 400 in a bay that’s pretty quiet because there’s little boat traffic. It’s actually pretty amazing to hear them so well.”