Everybody knows sea otters, right? Loves them. Videos of pairs holding paws and moms grooming pups on their tummies go viral. In her first year, Shedd’s rescued pup Luna, above, appeared on two lists of cutest animals in the world (deservedly) and was featured in the New Yorker.
These are not low-profile animals.
Then why each year do aquariums like Shedd, zoos, natural history museums, conservation organizations, researchers, educators and an adoring public devote themselves to a week of events and activities (between Sept. 18 and 24 this year) focusing on Enhydra lutris, as scientists know them?
Because sea otters are only an oil spill away from disaster. And as goes the health of this smallest of marine mammal species, so goes the health of one of the most productive marine ecosystems on Earth.
Sea otters are native to Pacific Rim nearshore waters, from Japan, where perhaps a dozen individuals have been sighted in recent years, to the eastern coast of Russia, which is home to about 20,000, across to Alaska and down the Canadian coast to Washington state, where the northern population numbers around 100,000, and then skipping to a section of central California coastline, where the southern population hovers around 3,000 animals. Historically, sea otters ranged all the way to mid-Baja California, Mexico.
Beginning with the arrival of Europeans in Alaska in the mid-1700s, North American sea otters were hunted ruthlessly and relentlessly for their dense, valuable fur into the early the 20th century. It was almost too late when they received protection under the International Fur Seal Treaty of 1911. In the United States, they got additional protection in 1972 from the Marine Mammal Protection Act. Most populations throughout the range gradually rebounded, including those affected by the catastrophic 1989 Exxon Valdez oil spill in Alaska, but the southern population has been slower to recover. Luna and our most recent rescued pup, Ellie, below, are members of that group.
Today’s southern sea otters are descendants of a lone colony of about 50 animals discovered near Big Sur in 1938. Southern sea otters received tougher protection in 1977 when they were listed as threatened under the Endangered Species Act. They are also protected by California wildlife laws. Data from the U.S. Geological Survey, which conducts aerial counts twice a year, show a slow but steady increase in the population for most of the last 25 years. The spring 2015 census, the most recent data available, put the population at 3,054, a figure approaching the level where the species could be removed from the threatened list but also what researchers consider to be close to the carrying capacity of the otters’ current limited range.
Recovery vs. risks
The southern population’s numbers are fairly stable. Still, such a small group is especially susceptible to a host of environmental and man-made factors. Federal, state, aquarium and university researchers are collaborating to understand how fluctuations in the population relate to these factors as they work toward the Southern Sea Otter Recovery Plan’s twofold goals of increasing the population’s numbers and expanding its range.
This remains the biggest threat. Otters and oil don’t mix. The southern population lives with the constant threat of spills from offshore oil rigs and tankers plying coastal waters. Oil saturates otters’ dense fur, compressing the insulating air that keeps them warm. Those that don’t succumb to hypothermia can die of organ damage after they ingest large amounts of the toxic goo as they try to clean their fur. At least spills involving sea otters have been rare in the last two decades.
As the only marine mammals without insulating blubber, sea otters need to eat a lot—25 percent of their body weight daily—to stoke their high metabolisms and stay warm in icy waters. Researchers are seeing higher mortalities, involving emaciated adults, in some of the most densely populated parts of the otters’ range, suggesting that resources are overtaxed. Other factors that can affect prey availability and foraging behavior are severe weather and periodic events like El Niños. Underweight and weakened animals are also susceptible to disease and toxins.
Harmful bacteria and parasites in human and animal waste are carried into nearshore waters by storm runoff and leaking sewage systems. These can cause fatal infections in sea otters.
More land-based contaminants, including fertilizers and nutrients from agriculture and lawn care, can create algal blooms that produce toxins. Sea otters have been found poisoned by these biotoxins, which they ingest with their food.
Scientists have documented an upswing in southern sea otter fatalities from shark bites. While not actually predation—great white sharks present in the northern and southern ends of the otters’ range apparently take “exploratory bites” but do not consume the animals—the outcome for the otters is usually the same. This new threat has resulted in local declines and impedes range expansion.
And in an example of an ecological domino effect, in southwest Alaska orcas have turned to preying on sea otters because they cannot find enough of their traditional prey, Steller sea lions. The sea lions have declined to dangerously low numbers, warranting listing as endangered under the Endangered Species Act, because their primary prey species have been overfished by commercial fishermen. The affected sea otter population plummeted and remains low, with a devastating effect on the area’s ecosystem.
Much more than a cute face
Sea otters are called a keystone species because, like the center, or key, stone that keeps an arch from collapsing, these little marine mammals are disproportionately responsible for the ecological balance of their nearshore habitats, including vast kelp beds. Sea otters are especially fond of the soft, succulent insides of sea urchins, which graze on kelp and, if left unchecked, can level these underwater forests. When southern sea otters disappeared along the Pacific coast, so did many of the kelp beds.
A wide variety of animals besides sea otters depend on this habitat, from sea stars and snails to bald eagles and gray whales, as well as kelp bass and rockfish species important to sport and commercial fisheries. We depend on kelp forests too. The sturdy strands of these giant algae slow powerful ocean currents, protecting coastlines from storm surges and erosion.
And as photosynthesizers, kelp absorb carbon dioxide and produce oxygen. Researchers at the University of California, Santa Cruz, calculated that kelp beds patrolled by urchin-hungry sea otters sequestered as much as 8.7 megatons of carbon—equal to the annual CO2 emissions from as many as 6 million passenger cars—compared to less than 2 megatons stored by kelp forests devoid of otters. You could call sea otters a force against climate change.
We do more than love otters
Shedd Aquarium has a long history of rescuing and rehabilitating aquatic wildlife. But in 1989, we got into sea otter rescue and rehabilitation by accident—a horrific accident: the grounding and rupture of the Exxon Valdez tanker, which disgorged 11 million gallons of crude oil into Alaska’s picturesque Prince William Sound, killing tens of thousands of marine mammals, birds, fishes and invertebrates.
Sea otters were especially hard hit as they surfaced for air and were coated in thick oil. Shedd experts joined the around-the-clock efforts at a sea otter rescue center set up near the scene of the disaster. The first sea otters in the Abbott Oceanarium when it opened were orphaned or abandoned pups from the oil spill, placed with Shedd by the U.S. Fish and Wildlife Service.
The federal wildlife agency has continued to rely on Shedd’s demonstrated ability to provide a home to sea otter pups that cannot be returned to the wild. Currently four of our five sea otters are rescues. Two came from Alaskan waters, while Luna and Ellie, our young southern sea otters, were saved by Monterey Bay Aquarium’s Sea Otter Program rescue team. (The fifth otter, from the Seattle Aquarium, is the offspring of an Exxon Valdez oil spill pup.)
At the same time that we have been privileged to give them a permanent home, our sea otters have provided us with opportunities to contribute to critical studies on the long-term effects of exposure to oil, expand our knowledge about animals from the northern and southern populations and advance veterinary expertise with them from dentistry to geriatric care.
Shedd Aquarium is a proud participant in Sea Otter Awareness Week, now in its 14th year. It allows us a chance to highlight the stories of our five engaging sea otters and the changing conservation challenges facing their counterparts in the wild. Check out all of our SOAW activities.
Everybody loves sea otters. But you can make a difference for them, even far from the Pacific coast, by choosing sustainable seafood, reducing oil consumption and supporting Shedd’s rescue and rehabilitation program. Until the oceans are safe for sea otters—and other marine wildlife—we need Sea Otter Awareness Week.
—Karen Furnweger, web editor