Chapter 4: Species in Danger

“How could it be that one small, cute and cuddly creature deserved such attention when there seemed to be so much uncertainty surrounding her fate? What was so special about 501, or sea otters in general, that made her worth such a Herculean effort?”

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The dedicated staff and volunteers at SORAC lavished countless hours of care, over a period of more than a year, to satisfy 501’s needs. In fact, 501 became part of a groundbreaking program at the Aquarium that a limited number of stranded pups are eligible for.

However, none of this devotion or special treatment could guarantee that 501 would survive. The process itself was arduous. In fact, when 501 became old enough, she might not even be deemed releasable. She would also face risks back in the wild. Of the pups raised as part of this special program, a little more than 50% survived their first year in the wild.

A pup tries to get some shuteye

How could it be that one small, cute and cuddly creature deserved such attention when there seemed to be so much uncertainty surrounding her fate?

What was so special about 501, or sea otters in general, that made her worth such a Herculean effort?

Scientists discovered that sea otters, called a keystone species, play a critical role in maintaining the health of giant kelp forests. These ecosystems provide homes to more different types of organisms than tropical rain forests.

Giant kelp forests provide an abundant nursery, as all kinds of sea life—including fish, crustaceans, and mollusks—find shelter, grow, reproduce, feed, and become food.

Find out how sea otters protect the kelp forests

But without sea otters, animals that devour giant kelp, such as sea urchins, can reduce a giant kelp forest to a barren rocky seafloor.

This has happened to many places where sea otters no longer exist. These depleted areas are called urchin barrens. Not just sea life loses out when this happens, but humans too, since people depend on healthy ocean ecosystems.

Sea urchins can devastate giant kelp

By eating sea urchins and keeping their population in check, sea otters ensure underwater forests of giant kelp don’t become underwater deserts.

And it turns out that sea otters are extremely good at chomping the prickly marauders. Some sea otters eat so many purple sea urchins that their teeth and bones turn purple. There was even a good chance that 501’s mother fed on sea urchins.

Looking out into Monterey Bay nowadays, the light brown canopies of giant kelp are not hard to spot just offshore, rocking back and forth in the waves. And wrapped in the fronds, you’ll find sea otters.

But decades ago, you would have had difficulty finding anything that looked like the kelp forests that prosper today. You also wouldn’t have found any sea otters.

The life of a sea otter is pretty tough now. But years ago, it was brutal. 501 is not only lucky to be alive, so is her entire species.

One of 501’s most vital adaptations for her survival in the cold ocean, almost doomed all sea otters.

Hard to believe these almost went extinct

The sea otter’s lustrous coat is the softest and plushest of all mammals. This fur can contain over 1 million strands of hair per square inch. By comparison, a human’s head of hair has about 700 strands per square inch. 

It was this same fur that got sea otters mercilessly hunted to the point where almost every last sea otter was killed.

Southern sea otters once roamed from Baja California, Mexico, up the coast of the US to the Pacific Northwest. While it’s hard to know exactly, their population was estimated to be as many as 20,000.

But that was before the hunts.

As early as the mid-1700s, fur traders from as far as Russia began hunting sea otters along the West Coast. The sea otter fur trade soon became a booming international industry.

A shipload of pelts commanded a fortune, so the hunt for sea otters was insatiable.

By the mid-1800s, the Southern sea otter population had been so decimated that the large-scale, commercial industry was forced to end. Still, the fur trading and hunting didn’t stop altogether and a single pelt became much more valuable.

In the early 1900s, southern sea otters were thought to be extinct.

Watch the history of the sea otter hunt

South of Monterey, in the mountainous, coastal region of Big Sur, near the iconic Bixby Bridge, Howard Granville Sharpe was used to watching stars, ships and whales go by with his telescope, from the porch of his cliff side ranch. But on 19 March 1938, he made a historic observation.

The forgotten coast

“I scanned kelp beds lying farther inshore,” Sharpe wrote about the event. “Slight movements there seemed inconsistent with normal rise and fall. I had no premonition that I was verging on a discovery destined to draw an army of spectators from the farthest reaches of the Earth. Certainly I couldn’t know that I would find a cool million dollars in furs, or be first to gaze at a sight unseen by mortals in a century.”

California’s coast is scenic but it’s rough, too

Sharpe found a tiny pocket of less than 50 sea otters that lived undetected by the general public. Some of the locals had known of their existence but feared for the safety of the persecuted sea otters. So, they had kept their secret of the last survivors.

The news of this discovery was met with more skepticism than attention. It seemed that poachers were the only ones that initially took it seriously. 

Not only had Sharpe caught poachers at work and found a bullet riddled sea otter carcass, he himself was shot at while trying to guard the sea otters.

Established in 1911, an international treaty that prohibited the sale of sea otter furs was in effect. But it was clear that the sea otters in Big Sur needed local protection. Soon after Sharpe’s announcement, the state government declared a large section of coastline a Sea Otter Game Refuge.

Eventually other laws followed. The Marine Mammal Protection Act was enacted in 1972. Five years later, in 1977, the Endangered Species Act covered sea otters.

Despite all of these protections, the southern sea otter population has been much slower to recover than marine biologists expected.

By the mid-1980s, the southern sea otter population had expanded from Sharpe’s approximately 50 animals to about 1,400. Along the coast of California, it is estimated that the carrying capacity for sea otters is 16,000 animals. This means there is a lot of room for the sea otter population to grow.

However, in just the last twenty years, there were two multi-year periods, 1997-1999 and 2009-2010, where the total sea otter population decreased each year. Scientists have yet to understand the reasons for these population decreases.

The sea otter population hasn't steadily grown

A 2012 census revealed that the total population had increased to 2,792, representing an annual growth rate of 1.5%.

No count was made in 2011, but, during this year, a record number of strandings, 335, occurred. Most of these stranded sea otters were either already dead or died shortly after stranding.  In the previous year, 305 sea otters stranded, 62 were pups. 501 was one of them.

Through diligent research, scientists are better understanding why individual sea otters are dying. A surprising result is that shark attacks are up. In 2010 and 2011, sharks caused 30% of fatalities, which is twice as high compared with only 15% in the late-1990s.

That still leaves 70% of sea otters dying of other causes. These causes may not be as fearsome as great white attacks, but certainly the end result is the same.

It turns out that many sea otters die from things so small—such as parasites, infectious diseases, bacterial infections, and harmful algal toxinsyou need a microscope to understand what’s going on.

Even in cases with apparent causes of death, like shark bites, mating trauma, emaciation, boat strikes, gunshot wounds, and oil spills, something less obvious may be at play.

Sometimes you need a microscope to see the threats Even sea otters can't escape plastic pollution Toxins from microcystin Toxoplasma: parasites from kitty litter


It is so important to fully understand the cause of death for sea otters that necropsies, autopsies for animals,are performed on almost every single recovered sea otter carcass.

With a better understanding of what happened to each individual sea otter, the ultimate cause of death becomes apparent– causes like increased urban runoff, habitat destruction, resource limitation, and decreased genetic variation.

Watch how biologists track the cause of death

By understanding what kills sea otters, we can better protect them against very real threats in their wild homes.

If she makes it back to the wild, there is no doubt that 501 will face these threats too. Once there, she will need all the help she can get.

Some gory details about being a biologist
back forward

California sea otters are protected from hunting, but humans are still having an impact on their survival. What humans put in their ocean homes can make animals sick. The ocean is downhill from everywhere, so it’s no surprise that clean fresh water is key to sea otter and ocean health. Clean fresh water is good for people, too.

Elkhorn Slough

You can help the ocean by keeping your watershed clean. Here are a few ways to get started:

  1. Choose certified organic foods
  2. Use less water
  3. Don’t use storm drains for chemicals or wastewater
  4. Refuse single-use plastics
  5. Pick up your pet’s waste
  6. Support legislation and politicians protecting water resources
  7. Protect open spaces
  8. Learn more about your watershed and the organizations protecting it. Find your watershed here:

Here are programs that can help you take action. Click on the link to learn more about them.

   The Nature Conservancy

On To Chapter 3 « Return to Slideshow

Special Features

This Page All

Chapter 1: The Ocean is Cold but Mom is Warm

Chapter 2: Less than Ideal Rescue

Chapter 3: Emergency Treatment

Chapter 4: Species in Danger

Chapter 5: No Substitute for Mom’s Cooking

Chapter 6: The Surrogate

Chapter 7: Furry New Friends

Chapter 8: Release

Chapter 9: A Wild Sea Otter

Video Clip: Pup Covers Eyes

As cute as sea otter pups are, when mixed with some absolutely adorable behavior, it makes this video clip one of the best.

Mini Doc: Keystone of the Kelp Forests

Professor Emeritus John Pearse talks about the dynamics of the kelp forest ecosystems along the California Coast, and the important role sea otters play to protect them.

Video Clip: Urchin Barrens

Kelp forests are amazingly diverse and bountiful ecosystems. More living organisms thrive in kelp forests than in rain forests. But without sea otters, spiny sea urchins would devour the giant kelp and destroy the ecosystems, creating underwater wastelands known as urchin barrens.

Video Clip: Lots of Sea Otters

The extraordinary fur of sea otters allows them to survive the frigid water of the Pacific Ocean. But this furry adaptation nearly lead to their eradication. Sea otter pelts were “brown gold.” And before effective laws could be put into place, southern sea otters nearly went extinct. The population is still slowly recovering after almost a century.

Video Clip: The Hunt History

Learn more about the great otter hunt, fur trade, and the rediscovery of southern sea otters off the coast of Big Sur.

Map: Big Sur, California

View Map: Big Sur in a larger map

Not too far south of Monterey, up and down mountains and cliffs along the scenic Pacific Coast Highway, you’ll find Big Sur. The southern sea otter was thought to be extinct. But a small group of sea otters, hidden here in Big Sur, survived the great hunts. The sea otters of this small group are the ancestors to all southern sea otters alive today.

Video Clip: The California Coast

California has a beautiful coast. But because of ocean conditions, it can be very rough. Winds, currents, and cold, deep water all have an effect. Sea otters must find a way to live within the waves and rocks.

Changes in Sea Otter Population

This graph shows how the total population of sea otters and the population of pups have changed over time. Both populations have grown since 1990. However, growth has been slow. In fact, during some years both populations have actually decreased. Scientists are still trying to understand why this is happening.

The population numbers that are graphed are the average of the three most recent years. So, for example, from the graph of total population in 2004, the number of about 2,500 is the average number of total sea otters counted in 2002, 2003, and 2004. Scientists use this three year average method because it gives more reliable results.

Graph source: USGS

Video Clip: Microscopic Threats

Take a look under the microscope at some of the microscopic threats faced by sea otters.

Video Clip: Otter with Plastic

While seeing a sea otter playing with a plastic bottle might seem funny, the truth is that massive amounts of plastics are flooding the oceans and killing massive numbers of animals, including—but far from limited to—birds, turtles, fish, and even whales.

Mini Doc: Microcystin

Microcystin is a freshwater toxin that has made its way from inland water sources into the ocean, where it’s killing sea otters. Learn how scientists pinpoint the toxin sources, and what they’re doing to help mitigate the effects. Warning: this video has some graphic content.

Mini Doc: CSI

At the California Department of Fish & Game’s Wildlife Veterinarian Lab in Santa Cruz, a team of scientists performs necropsies (animal autopsies) on sea otters to find out what is killing this threatened species. Warning: this video has some graphic content.

Mini Doc: Profile of a Marine Biologist

Sea otter biologists don’t all do the same job. Colleen Young, a sea otter biologist with the California Department of Fish & Game, explains what her job is, working to uncover the causes of sea otter deaths. Warning: this video has some graphic content.