Human activities threaten shore-loving sea mammals.
Thursday, March 1, 2007
THE YOUNG SEA LION SCOOTS OUT OF HIS PLASTIC CRATE on strong black flippers, one dangling an orange ID tag, and hauls his blimp-shaped, butterscotch-colored body down the boat ramp at Whaler’s Cove in Point Lobos State Reserve. He sniffs the wet concrete and the air, wobbling his head side to side as if he’s listening to groovy music, then looks over his shoulder at the humans watching him. Volunteers with the Marine Mammal Center form a wall behind him with shield-like boards, herding him down the ramp toward the water.
“This is the emotional payday that we’re working for,” says Sue Andrews, the only paid staffer at the Sausalito-based Center’s field office in Monterey. The rehabilitation clinic’s volunteers picked up the sea lion in Pebble Beach about six weeks earlier. Soon after admittance the yearling had a seizure, a a classic symptom of a condition called domoic acid poisoning. He was likely exposed to the neurotoxin as a fetus when his mother encountered harmful algal blooms, Andrews explains.
Along with the sea lion, two elephant seals will return to the ocean today. The Center’s staff has treated one of them for lungworm, and picked up the other because he had “stranded” himself on the beach in Monterey. The Center administers only to stranded sea mammals, most of whom are sick, brain-damaged or badly adapted to life at sea. Only half live through rehabilitation to attain a clean bill of health and develop the foraging skills needed to return to the wild.
So today is a joyful day, and not only for the Center volunteers and staff. Two Point Lobos rangers and a dozen visitors perch on algae-slick boulders, their coats pulled tight against the brisk air, cheering the animals on as they heave clumsily, hesitantly toward the water. A sea otter swims within a hundred yards of the boat ramp and floats on its back, grooming.
But the elation of the day is cut with some apprehension. Even as the rehabilitated animals return to their marine home, they face uncertain futures. Away from the small freshwater pools at the Marine Mammal Center, they’ll risk not only predation by killer whales and white sharks, but also a range of human-driven threats, from pollution to parasites, from undernourishment to fishing nets.
Contaminants, pathogens, depleted food sources and fishing nets have made the near-shore habitat a dangerous place. And the sea mammals who breed there—otters, sea lions and seals—seem to be hurting.
GENA BENTALL PLANTS HER BROWN HIKING BOOTS on the pavement and peers through a scope at a group of five adult female sea otters floating in the near-shore waters of the Hopkins Marine Reserve, one with a pup. She pans an antenna slowly from left to right, scanning through a series of frequencies, and when it picks up a signal, she logs the radio-outfitted otter’s coordinates.
The oblivious subject floats face-up on the water, grooming the pup on her belly. The pup rolls off and its mother does somersaults in the water, blowing on her coat to keep it air-tight and warm, then dives to forage. Her pup—held to the surface by its buoyant natal coat—squeaks.
As she descends to look for shellfish, the mother otter carries instruments implanted in her abdomen by veterinary surgeons with the Monterey Bay Aquarium’s Sea Otter Research and Conservation program (SORAC). The radio tracks her movements along the coast, and a time-depth recorder logs her dives into the sea. “It gives us the most information possible to make good policy decisions for sea otters,” says Bentall, a SORAC research biologist.
That otters are here at all is the result of such conservation efforts, which have been ongoing for much of the last century. Researchers estimate that there were once more than 16,000 otters comprising the southern branch of the species, often referred to as the California otter. But the same luxurious coat that helps them survive in cold Pacific waters almost did them in. The Russian fur trade of the 1700s and 1800s nearly wiped out the species, and by 1914 the otter was gone from California—except for about a hundred who clustered near Big Sur.
Through aggressive conservation measures, the species began to rebound. The designation of protected marine areas beginning in 1913 saved key sea otter breeding grounds, and the Marine Mammal Protection Act of 1972 made it a crime to kill them. Their 1976 listing as “threatened” under the Endangered Species Act compelled the US Fish and Wildlife Service to develop a management plan to bring up their numbers. In 1990, the state banned the use of gill-nets within the otter’s range, and in 2000 the International Marine Organization adopted “recommended tracks” to keep cargo vessels and oil tankers out of the otter’s habitat, reducing the chance of deadly oil spills.
All of these efforts worked—up to a point. Last spring, the US Geological Survey counted almost 2,700 otters living along the California coast from Half Moon Bay to Point Conception. While that’s more than double the number counted in 1983, wildlife managers have been disappointed in the southern species’ rate of growth—a sluggish average of about 3 percent per year, compared to almost 20 percent for recovering northern populations in Washington and Alaska.
Early in these efforts, scientists predicted that the southern sea otter count would grow to 10,000 by the turn of the millennia. It has not come close to that number, and since 2004 the population has actually decreased by several hundred otters. “It’s just not growing at the rate we expected it to grow,” Bentall says.
That may mean that the waters off the Central Coast do not provide enough food for more than two or three thousand otters. In science speak, the area may already be at carrying capacity, a poor reflection on the state of our coastal ecosystem.
If 16,000 otters once populated California, and, as the US Fish and Wildlife Service recently estimated, more than 8,000 otters could thrive here, what’s stalling the southern sea otter’s population growth?
“Something has probably changed within this habitat that makes it really challenging for that many animals to coexist,” Bentall says. She ticks off some of the potential culprits: contamination, commercial fishing, recreation, disease.
LILIAN CARSWELL, A US FISH AND WILDLIFE SERVICE BIOLOGIST stationed in Santa Cruz, says it’s possible that sea otters are simply at carrying capacity for natural reasons, and not because people are depleting their food sources. “It seems likely that they can out-compete fishermen,” she says. But Bentall suggests that studies of otters’ body conditions and the amount of time they spend foraging show otherwise. She says that the state of their food supply—bottom-dwelling invertebrates such as urchins, crabs, snails, abalone and clams—may be limiting the otter population’s growth within its current range.
The food that local otters are able to forage is often loaded with poisons: synthetic chemicals used to make fire retardants, pesticides, insulators, transformers, plasticizers and petroleum products. Even DDT, a pesticide banned in 1972, and PCB, an industrial compound banned in 1979, continue to linger in the sea.
Researchers who have tested healthy sea otters in Monterey Harbor, Elkhorn Slough and Santa Cruz Harbor have found contaminant levels 50 to 100 times higher than those in Alaskan sea otters, according to David Jessup, a senior wildlife veterinarian with the California Department of Fish and Game. “We don’t know what subtle influences that has on their immune response, their reproductive and endocrine systems,” he says.
Some researchers suspect that sea otters whose immune systems have been weakened by exposure to contaminants and undernourishment are more vulnerable to pathogens such as >>Toxoplasma gondii, a parasite common among land animals but particularly harmful to otters. Cats both domestic and wild contract Toxoplasma from mice or birds and pass millions of eggs in their feces, which then flow through streets, sewer pipes and rivers into the sea. Mussels, clams and oysters pick up the parasite in their tissues, thus infecting the otters that eat them.
Some otters who carry Toxoplasma can live for a long time with few symptoms, but others develop shaky paws and lose their inhibitions around dangerous things like people, boats and sharks. Over time, Toxoplasma may cause an infected otter’s brain to become inflamed and scarred, which leads to seizures and eventual death. “Once your brain’s fulla holes, it’s pretty hard to come back,” says Jessup, who supervises necropsies on sea otter carcasses recovered from the Central Coast.
Of the 80 to 90 fresh otter carcasses Jessup’s lab analyzed last year, about a quarter had died from either Toxoplasma or a similar parasite. Together, the parasites comprise the single biggest identifiable cause of death among sea otters, Jessup says, although fecal bacteria from humans and livestock also make otters sick.
The convergence of food shortages, contaminants and disease have researchers concerned about the future not only of sea otters, but also of other top predators in the marine food chain, including humans.
“They’re acting as a very interesting sentinel animal, picking up everything that’s going into the California environment,” Jessup says of sea otters. “All that stuff that’s making them sick and killing them is eventually going to be making us sick and killing us. They’re doing us a favor by telling us this, and we ought to be listening.”
To some extent we are listening, even if it’s just because sea otters are so charming. Glossy magazines and TV documentaries give the charismatic animals play as their population hovers in the low thousands. The Monterey Bay Aquarium, which hosts almost 2 million visitors a year, permanently exhibits five resident female sea otters and is planning to open a freshwater otter exhibition on March 31. Spokeswoman Karen Jeffries says that in 2006, visitors ranked otters as the second most interesting animal at the Aquarium. (Jellies edged them out by 1 percent.)
SORAC biologist Bentall wonders whether people’s natural attraction to sea otters may lead us to underestimate them as simply cute. “They’re just tremendous animals,” she says rather defensively. “They’re intelligent, they’re resourceful, they’re wonderful mothers, they’re survivors against incredible odds. I’ve been very lucky to be able to see them like that rather than as some kind of postcard image.”
Then she pauses, her eyes on the road as she drives to the next otter-sighting location, and a smile erases the worry on her face. “But I’ve been at this job too long if I ever stop thinking they’re cute.”
AT WHALER’S COVE, THE YOUNG SEA LION becomes more excited as he approaches the edge of the water, his head weaving faster. A small wave laps at his flippers and he lowers his nose to the water, sniffing. As the wave recedes he slides into the sea with it, transforming from comical to graceful in an instant, his furry butterscotch coat turning chocolate brown.
The crowd cheers, and Ranger Chuck Bancroft passes out Oreos—a tradition, he jokes.
Even though she’s all smiles too, the Center’s Sue Andrews worries about the yearling. That head-weaving wasn’t normal. And if Center vets correctly diagnosed him as having been exposed to domoic acid in utero, the odds of survival may be against him.
The California sea lion population—decimated by bounty hunting from the 1920s to the 1950s—has generally been on the upswing since the enactment of the 1972 Marine Mammal Protection Act, rebounding from about 12,000 pup births in 1975 to more than 56,000 in 2001. That indicates a current population of more than 240,000, according to a recent NOAA report. Those numbers keep the California sea lion off the endangered species list, but domoic acid poisoning and other threats keep researchers concerned about the species’ future.
Domoic acid is a neurotoxin produced when a certain kind of algae blooms. When sea lions gobble the mussels, anchovies or clams that have eaten the algae, the toxin affects their brains and they get sick. A poisoned sea lion might weave and bob her head, slobber and bug out her eyes, appear disoriented or have seizures. If she’s pregnant, the toxin will be passed to her fetus.
Although domoic acid is naturally-occurring, it may be proliferating because of increased fertilizer, sewage and stormwater runoff into the sea. These nutrients feed the harmful algal blooms, which sickened almost 300 California sea lions in the last two years.
Sick sea lions often strand on public beaches, and that’s when the Marine Mammal Center steps in. Volunteers transport the animals to the Center’s clinic in Sausalito, where veterinarians administer a vitamin-rich solution to flush out the neurotoxin and a medicine to control the seizures. As with rescued sea otters, fewer than half of MMC’s poisoned sea lion patients make it through rehabilitation, and the long-term survivors are often left with brain damage.
Dr. Frances Gulland, a MMC veterinarian, has focused on another pathology hitting sea lions: a cancer affecting their uro-genital tracts. Since they began tracking the disease in 1993, MMC’s veterinarians have found such cancerous tissue in almost 20 percent of adult sea lions stranded along the California coast every year—a number that Gulland says is “extremely high for a wild animal.” More unusual still, every sea lion who has died of the cancer has also had sexually transmitted herpes, and unusually high levels of the persistent pollutants PCB and DDT.
In the ’70s, DDT caused massive sea lion abortions that littered the southern California coast with the bodies of prematurely born pups. Although the levels aren’t nearly as high today, most California sea lions still have DDT in their bloodstreams. But it’s the PCBs that worry Gulland, who hypothesizes that the contaminant interacts with herpes and genetic predispositions to give sea lions reproductive tumors. She also warns that the same could happen to us.
“These PCBs are acquired in the sea lions’ diet—a diet that is similar to humans’,” she says. “The sea lions are providing us with an early warning of toxic compounds in our food chain.”
California sea lions also battle pathogens such as the kidney-attacking bacterium Leptospira interrogans, the flipper-blistering San Miguel Sea Lion Virus, the lump-inducing Seal Pox Virus, and a parasitic hookworm that burrows into a mother sea lion’s mammary glands and secretes into her nursing pup.
Commercial fishing adds another hurdle to the sea lion’s survival. NOAA estimates that gillnets and driftnets caused more than 6,300 sea lion deaths between 1997 and 2001—in addition to the toll taken by fishermen annoyed with the competition. While it’s generally illegal to shoot sea lions, NOAA recently tweaked regulations to allow fishermen to apply for permission to shoot sea lions that compete for their catch.
Perhaps most deadly to the species is El Niño. During El Niño years, the waters warm up and the prevailing winds drop, which reduces the upwelling of nutrients that feed phytoplankton. Fewer phytoplankton means fewer zooplankton, which means fewer fish that feed sea lions. Like a chubby kid stealing bread from the pantry, El Niño pinches the bottom out of the food chain and makes sea lions and other top marine predators work harder for their supper. Data from the National Oceanic and Atmospheric Administration (NOAA) show that pup births plummeted during the El Niño years of 1983, 1992 and 1998.
The cyclic warming of the ocean is a naturally occurring phenomenon, but human-driven climate change is making it happen more frequently. Daniel Costa, a professor at the UCSC Center for Ocean Health, found that during 2004-2005, when the sea was unusually warm, male California sea lions traveled twice as far and spent three times as long out at sea than they had the previous year. Costa says this was not an official El Niño year, but a year in which “El Niño-like conditions” nevertheless appeared.
“Our best guess is that the sea lions were looking for food farther off at sea,” he says. “The climate change scenario that we’re looking at indicates that El Niños, or El Niño-like conditions, will become more common. And neither of those is a good thing.”
SOON AFTER THE SEA LION SWIMS OUT INTO WHALER’S COVE, a female elephant seal flubs out of her plastic carrying case and lies still on the boat ramp, looking confused. To her right, Marine Mammal Center volunteers shake a molting juvenile male out of his case, and he too lies dazed for a moment. Then the female flops toward the male and the two raise their heads, bellowing at each other. Center volunteers give the pair a moment before closing in behind them with herding boards, nudging them toward the water’s edge.
The waves lap against the seals’ streamlined bodies, and still they hesitate. But eventually, much to the relief of the humans gathered around, they slip into the cold sea and swim away. “They’ll go find their own kind,” MMC staffer Sue Andrews says with a half-smile, “and hopefully not come back.”
It’s unusual for ocean-traversing elephant seals to show up alone on public beaches—reason enough for MMC to respond when these two stranded in Pacifica and Monterey. Northern elephant seals generally stick to the open ocean, coming ashore only to breed in the Channel Islands, Point Año Nuevo and Southeast Farallon Island. Like sea otters, they were hunted to near extinction, rebounding from about 100 in 1900 to 100,000 in 2001, though their growth rate has fallen in recent years.
SEA MAMMAL RESEARCHERS ARE LESS WORRIED about harbor seals, which locals can often find sunning their plump, black-and-white-mottled bodies on shoreline rocks. Though their California population, at about 34,000, is tiny as compared to sea lions, harbor seals have been flourishing locally since the passage of the Marine Mammal Protection Act in 1972. Several hundred have made the Monterey Peninsula their year-round home, according to marine scientist Jim Harvey, who works out of San Jose State’s Moss Landing Marine Lab.
Although harbor seals face the standard perils of predation, diseases and entanglement in fishing nets, Harvey doesn’t see any particular factor threatening them on an epidemic scale. “They’re in pretty good shape,” he says.
Our marine neighbors even escape the cyclic tantrums of El Niño, Harvey says, because they eat flatfish, octopus, squid and herring—species not heavily impacted by El Niño-induced nutrient shortages. In this regard, harbor seals are lucky pups.
The biggest threat to them, in fact, is people. Harbor seals are coastal animals—they live and breed on local beaches, dangerously close to curious humans. Skittish mother seals will temporarily abandon their pups if people come too near, sometimes prompting well-meaning beachgoers to pick up the whiskered babies. (That’s harmful to pups and illegal under the Marine Mammal Protection Act.)
The problem of human disturbance is so prevalent that the Marine Mammal Center launched a campaign called “Leave Seals Be,” encouraging coastal residents to call the Marine Mammal Center rather than interacting with harbor seals. “Every season, a large number of harbor seal pups we rescue have been separated from their mothers because they were removed from beaches or were harassed,” says the Center’s Shelbi Stoudt.
Fur seals—more closely related to sea lions than harbor or elephant seals—are scarce along the Monterey Bay shores, generally migrating no farther south than Point Año Nuevo and San Miguel Island. But recently the Marine Mammal Center has responded to a surprising 32 calls about locally stranded fur seals, 23 of whom survived. That’s more than the facility can handle, leading staff to hand off six to UCSC’s Long Marine Lab. The prevalence of undernourished fur seals on local shores may signal that an El Niño event is coming, says Costa.
WHEN WE LOOK AT THE COMPLEX WEB OF FACTORS that influence sea mammal health, a deeper lesson emerges, and one that’s harder to swallow: Industrialized society is threatening marine life from multiple angles. If a California sea mammal goes extinct, it will likely be death by several deep cuts.
For harbor seals, the solution may be as simple as keeping people off their breeding grounds and out of their ocean digs. In the 1960s, harbor seals refused to give birth at the heavily visited Elkhorn Slough, Harvey says, but when the California Department of Fish and Game imposed restrictions to give seals undisturbed pupping areas, female seals leapt on the opportunity. Now 50 to 70 pups are born there annually.
And as state wildlife vet David Jessup notes, the prevalence of parasite infections among threatened sea otters can be curbed with improvements to urban stormwater systems and sewage plants, and better practices on farms and golf courses. But unless we clean the oceans of the contaminants that suppress their immune systems, he warns, otters will likely remain susceptible to other diseases.
If sea otters go down, sea lions may suffer too. Otters eat urchins that eat kelp, so healthy otter colonies usually mean flourishing kelp forests. As Harvey of Moss Landing Marine Lab notes, kelp forests nurture rockfishes, a favorite food of sea lions.
Ambitious conservation laws such as the Marine Mammal Protection Act and the Endangered Species Act have allowed sea mammal populations to rebound dramatically from their depleted states 35 years ago. As Congress moves to reauthorize the MMPA, advocates hope that the regulations protecting sea mammals will only get stronger. Meanwhile, a consortium of locally-based research institutions and government agencies collaborate through the Sea Otter Alliance to nurture the threatened population. Citizen groups such as Friends of the Sea Otter and Surfrider chip in, waging public awareness campaigns and lobbying for progressive action.
Just last year, we saw how local actions can inspire big change. After visiting the Monterey Bay Aquarium’s resident sea otters and learning about the threats they face, 5-year-old Will Jones tearfully asked his father to “do something” to help them recover. His dad, Assemblymember Dave Jones (D-Sacramento), took the request to heart, co-sponsoring a bill introduced by Santa Cruz Democrat John Laird.
The legislation requires kitty litter manufacturers to advise consumers against dumping their cats’ waste in toilets or storm drains, increases the fine for killing a sea otter, creates a program to research non-point source pollution, and establishes a voluntary tax check-off to support sea otter research. Last September Gov. Schwarzenegger signed the bill into law.
As overwhelming and multifaceted as the problems may seem, Costa hopes that people won’t give up on our marine mammal neighbors. “I personally feel that our fate is intertwined with them,” he says, “because we rely on many of the same aspects of the Central Coast. And those things are probably going to change.”
SEVERAL HOURS AFTER BEING RELEASED INTO THE SEA, the female elephant seal returns to Whaler’s Cove, heaves herself up the boat ramp and flops into the parking lot, where a ranger discovers her. Marine Mammal Center volunteers return to pick her up, re-releasing her on the other end of Point Lobos at Weston Beach, and hope she hasn’t become too comfortable with humans to survive in the sea—that she hasn’t replaced her own wild senses with faith in the species that simultaneously loves and plagues her.