[Narrator] Sea otters.

Their antics are adored by many along California’s central coast.

[Brent] They are cute, they are furry, they look like you just want to give them a hug.

But they are voracious animals.

They are remarkable predators in the ocean.

[Gena] Their appetites are ridiculous.

[Michelle] There's actually over 60 different species of prey items that otters eat.

[Gena] Things like crabs, worms, clams, marine snails, obviously they're really famous for being big consumers of sea urchins.

They have an extremely high metabolic rate.

[Brent] They eat 25% of their biomass every day just to stay alive.

It's about 20, 25 pounds of food that they need to eat.

[Lilian] They don't have blubber to help keep them warm.

And so they have to rely on their fur and their high metabolism.

[Jessica] Sea otters have the densest fur of any mammal.

They have approximately a million hairs per square inch.

And it was this really dense fur that really attracted the fur trade, and that was part of their demise.

It was referred to as soft gold because it was so valuable.

[Lilian] The global sea otter range used to be throughout the entire North Pacific, from Japan to halfway down Mexico.

[Gena] And that was probably 200, 300 thousand animals.

[Narrator] But the booming fur trade in the seventeen and eighteen hundreds nearly exterminated sea otters in the North Pacific, until the furry marine weasels received protection from hunting under the International Fur Seal Treaty in 1911.

[Lilian] After the fur trade, sea otters were reduced to just a few remnant populations.

And so, the southern sea otter was reduced to just a single little population off the coast of Big Sur in Central California.

[Narrator] It’s estimated that only about 50 animals survived along Big Sur’s rugged coastline.

[Gena] Since then all of the populations have recovered to some extent, but the southern sea otter here in California has been the slowest to recover and has recovered the most limited percentage of its historic range.

[Michelle] They have a difficult life.

[Narrator] Despite the many challenges sea otters face, as keystone predators they play a vital role in the ecosystems they inhabit.

[Jessica] And these are ecosystems that many other animals and humans depend on.

[Michelle] They have a lot of jobs that they do, and people don't realize it.

[Narrator] How do sea otters impact the environments they live in?

And what is keeping them from expanding their range in California?

[Announcer] Major funding for this program was provided by the Batchelor Foundation encouraging people to preserve and protect America’s underwater resources.

Additional funding was provided by Trish and Dan Bell and by the Parrot Family Endowment for Environmental Education.

[Narrator] In the quaint town of Morro Bay, on California’s central coast, curious onlookers delight in catching a glimpse of the southern sea otters that rest along the waterfront.

[Gena] They wanna get in and get the photo.

And at that point, when the animal is resting is when they're most vulnerable to the impact of someone just getting too close.

[Narrator] Given the sea otters’ fast metabolism and lack of energy stores, each disturbance that leads them to burn calories is detrimental to their longterm health and survival.

This is especially true for sea otter moms, who need to consume 3040 percent of their bodyweight daily to feed themselves and their pup.

[Gena] And they can be really extra vulnerable at that time.

And that's when people love them the most, right?

So just asking folks not to love them to death.

They'll look at you, and that's a warning sign.

So we're always telling people, be alert for that and then stop if you see it and back away.

Just give them space.

[Gena] Perfect timing!

[Narrator] To get the word out, Gena works closely with businesses that are involved in marine recreation.

[Gena] I just wanted to bring you your flag.

[John] Awesome!

[Narrator] Outfitters who promote respectful wildlife viewing are eligible for the Community Active Wildlife Stewards, or CAWS, certification.

[Virginia] CAWs has given us great verbiage and ways to approach people so that we can, you know, really get the point across to them without offending anyone, so to speak.

So it's been a huge asset for us.

[Narrator] In addition to outreach, Sea Otter Savvy is also conducting research.

Volunteers regularly measure the level of sea otter disturbance at different sites.

[Volunteer] Let me do the stimuli for you on the shore.

One, two, three, four, five [Gena] And they do a twohour session where they scan from one side to the other every 15 minutes.

[Narrator] During those scans, the team records the sea otters’ activity and their distance to human stimuli such as onlookers, boaters or kayakers.

[Gena] We've collected data at nine different sites all along the central coast.

And so we have this huge data set over ten years recording all kinds of elements of sea otter disturbance by human activities, and the average, across all of our sites, is six disturbances per day.

So it's not that one disturbance, it's the one after and the one after that, and the one after that.

And that adds up to a cumulative impact to these animals.

[Narrator] A few hours north along the coast, visitors to the Monterey Bay Aquarium have a chance to see and learn about rescued sea otters up close.

[Jessica] As sea otters stranded and needed help, we were learning how best we could give them the care and get them back out to the wild.

In the early 2000s, we started this new program that we call our Surrogacy Program, where we pair these orphan pups with our female adult sea otters that live here at the aquarium.

[Narrator] When an orphaned pup arrives at the aquarium, the staff takes great care to keep the animal as wild as possible.

[Jessica] We provide handson care while wearing disguises so that the pup doesn't associate people as a mother.

We're having to bottle feed the pup, groom its fur.

It's very dependent.

[Narrator] Once a pup is about two months old and can eat solid foods, the team introduces it to a surrogate mom.

[Jessica] We've had really good success with them being super ready to start sharing food, grooming the pup, all those great behaviors.

And we'll watch as they form this maternal care bond and continue to care for them until the pup is about six months old.

That's about the age that they wean or separate from their mom in the wild.

And so after that they're practicing all those essential skills that they learned and getting ready to go back out into the wild.

[Narrator] When a pup is ready to be released, the aquarium’s veterinary team gives the animal a thorough health exam.

[Jessica] And they will do a surgery to implant the radio transmitter.

And that transmitter lasts for three to four years.

And that really helps us find the animal once they're back out in the wild.

Each otter has their own unique frequency, and we can go along the shoreline and listen to all those different frequencies.

And if they're in the area, we'll get a beeping signal.

And that helps us know what direction they're in.

And then we can start looking with really highpowered telescopes to actually try and find that otter and see what they're doing and how they're doing.

[Jessica] Oh there she is.

She’s hauled out.

[Jessica] And we’ll follow them every day for two weeks, to really make sure they're able to find food, that they're not getting too stressed.

And then after that, they're considered officially released and a wild otter again.

And we'll continue to follow them to see how they're surviving, how they're reproducing and where they're moving to in the range.

[Narrator] Early on, the aquarium staff noticed that many of the released otters moved to Elkhorn Slough, an estuary about 30 minutes north of the aquarium.

[Jessica] And so we just started going there directly, and it was a very low population of sea otters at that time, maybe 20 were living in the estuary.

And so for over 15 years, we focused our release of those surrogate reared otters into the estuary.

And about 37 of them were released over that time, and we also saw the population grow to over a hundred.

[Michelle] Right now, Elkhorn Slough is the highest density of sea otters in one particular place.

[Narrator] This makes the slough a great place to study social behavior and chronic stress in sea otters.

[Lilian] And what I would really like to know is how important social bonds are to sea otters.

First of all, whether those bonds even exist, who's affiliated with who, how long those affiliations last, and whether there's any genetic basis to it.

[Narrator] In addition to being the Southern Sea Otter Recovery and Marine Conservation Coordinator for the U.S.

Fish and Wildlife Service, Lilian Carswell is working on a Ph.D. at UC Santa Cruz.

[Lilian] We know that sea otters have lots of stressors in their environment.

There's food limitation, there's disease, there's human activity, there's predators.

How can they rely on each other and perhaps have improved fitness because of these relationships?

[Narrator] To gain insight into sea otter relationships, Lilian, together with her collaborators, attached unique flipper tags to 90 otters so far, making it possible to identify and closely observe individual animals.

[Lilian] We have people going out several days during the week, and we're getting the GPS location of the animal, getting its behavior, whether it has a pup, and especially who it's with.

And sea otters tend to do most activities on a solitary basis, but when they rest, they like to be together.

And so is there a regular group of otters or are they moving around between these different groups?

And so our initial results indicate that there really are clusters of animals that do tend to show up together.

[Narrator] Lilian is also analyzing hair and whisker samples to evaluate cortisol levels as a measure of chronic stress.

Sea otters in Elkhorn Slough appear habituated to human disturbances from kayaks and boats that keep a proper distance.

[Lilian] But are those habituated sea otters actually experiencing elevated levels of chronic stress is something I would like to understand.

[Narrator] As the number of sea otters has grown to more a hundred, the slough itself has changed as well.

Seagrass is healthy and has spread, despite receiving lots of nutrients from agricultural runoff that usually causes algal blooms.

[Brent] The algal blooms in theory should be totally smothering the seagrass.

And in fact, it was in the early eighties, it was almost totally gone from the ecosystem.

[Narrator] So what changed that suddenly allowed seagrass to thrive?

[Brent] The seagrass are home to these really important invertebrates.

They're herbivores that eat the algae that grows on the seagrass.

[Narrator] But an overabundance of crabs which eat these herbivores led to their decline until sea otters returned to munch on the crabs, reducing their numbers instead.

[Brent] And that allows these little invertebrates to clean the seagrass.

[Narrator] It had been well documented that the presence of sea otters has positive impacts on kelp forests, since the otters forage on urchins which like to eat kelp, but this was the first time their importance in seagrass beds was documented as well.

[Brent] It was a huge surprise.

And so it kind of opened up these whole new doors of what a sea otter can actually do in multiple ecosystems.

[Narrator] And the sea otters didn’t just positively impact the seagrass.

[Brent] The salt marshes have this huge threat, which is erosion.

And the erosion has been happening for about 80 years in the estuary due to human changes with the hydrology.

But also all these nutrients and algal blooms we think are stimulating burrowing crabs that burrow into the salt marsh.

When they are left unchecked by predators, they can just deteriorate, create this almost like swiss cheese effect where it destabilizes the banks of the shoreline.

[Narrator] But as sea otters started spending time in the salt marsh, they began feeding on these types of crabs.

[Brent] And all signs pointed to the sea otters actually slowing down the erosion of a system.

And that was the first time that it had ever been documented for a top predator in nature.

[Narrator] As the number of sea otters in the slough has increased over the last 20 years, the amount of prey available for each animal has declined.

[Michelle] They're starting to look a little bit skinnier, and they're getting different food, less caloric value prey items.

[Narrator] Sea otters in the slough and along much of California’s central coast have reached what is known as carrying capacity, meaning their numbers are as high as they can get unless the food supply increases.

[Narrator] Despite this, sea otters have not expanded their range to the north or south of where they are found currently.

[Jessica] Right at the northern and southern extent of the range is the same area where we have a high risk of shark mortality.

[Gena] Shark mortality has created this kind of gauntlet that's too hard for them to get past.

White sharks, they're encountering sea otters fairly frequently, mistaking them for a nice juicy, blubberfilled seal, and instead they get this hairball of a sea otter.

But unfortunately, that tasting bite is very likely to be fatal for the otter.

[Melissa] So as a primary cause of death right now, white sharks seem to be one of the big drivers.

[Narrator] Melissa Miller is a Wildlife Veterinarian and Pathologist for the California Department of Fish and Wildlife Office of Spill Prevention and Response.

[Melissa] When there's not spills to respond to, a big part of what our duty is, is to recover wildlife that have been found live stranded or dead stranded along the coast, and to do postmortem examinations to figure out the cause of death.

[Narrator] In an average year, Melissa’s lab examines around 400 dead sea otters.

[Melissa] And to put things in perspective, the total population of sea otters here in California, is just a little over 3,000 animals.

The southern sea otter populations have been protected for well over a hundred years now, but population recovery has been relatively slow.

And, and one of the factors driving that is continuing high mortality.

[Narrator] Harmful algal blooms are one of the big threats to sea otter survival.

[Melissa] And probably foremost among those is something called domoic acid.

[Narrator] Domoic acid accumulates in shellfish which eat the algae.

[Melissa] And quite often we have fisheries closures to protect people.

And the thing is, otters can't get out of the water and go to McDonald's when those blooms are occurring.

A lot of the prey species that sea otters favor are really good at concentrating that particular toxin and very slow to eliminate that toxin from their body.

Domoic acid has the ability to cause long term and potentially lifelong issues in animals after a single or multiple lowlevel exposures.

[Narrator] Another big issue impacting the health of sea otters is a variety of parasites.

[Melissa] The one that I focused quite a bit of my energy on is one called Toxoplasma gondii.

And that particular parasite is one that has a very interesting part of its lifecycle in that only cats, such as domestic cats, bobcats, and mountain lions, are capable of shedding the tough environmentally resistant egg stage of the parasite.

And these cats are getting infected with this parasite through their prey, typically.

An infected cat may show absolutely no clinical signs but shed millions of these tough, very environmentally resistant eggs that we call oocysts out into the environment.

And these oocysts are designed to survive under very adverse conditions for months to years.

[Narrator] These oocysts get washed into streams and rivers, eventually making their way into the coastal ocean, where they get taken up by snails and filterfeeding bivalves.

[Melissa] They don't get infected, but what they're doing is concentrating it, and then serving as a source of exposure for sea otters.

[Narrator] And since 2020, a new strain of toxoplasma that is much more pathogenic has been showing up in a few sea otters.

[Melissa] And it was killing prime aged, healthy adults very quickly, very acutely.

[Narrator] And toxoplasma isn’t the only parasite to impact sea otters.

[Melissa] There's a related one called Sarcocystis neurona that is associated with possums, which is an introduced species here in California.

It's the same sort of idea as cats, except that you insert the possum into the lifecycle.

[Narrator] Other parasites impacting sea otters via the same land to sea pathway are spread by racoons and rats.

[Melissa] What's been kind of shocking about this is, especially if it's an adult otter here along the coast of California, chances of it being infected with one or both of these landbased parasites is about 65 to 70%.

It still kind of blows me away to think about that.

And it's really helped me to understand as a veterinarian how interconnected the land and the sea are and how important it is that we pay attention to everything that we're putting into freshwater habitat.

[Narrator] For southern sea otters to continue to recover, the population needs to expand its current range, something that hasn’t happened in 20 years, and is unlikely to occur naturally given the increased shark attacks along its boundaries.

[Brent] If there's like a catastrophic oil spill or some sort of disease outbreak, it could in theory wipe out the whole population.

[Lilian] So the U.S.

Fish and Wildlife Service is considering sea otter reintroduction.

We were tasked by Congress in 2021 to produce a feasibility assessment.

And we particularly focused on Northern California and Oregon because that's the largest gap in the existing range that we still have.

And we determined that it is biologically and logistically feasible, but that we need to investigate the potential socioeconomic impacts further.

[Gena] The biggest, most knowledgeable experts on different aspects that this reintroduction would involve are all coming together and working on this conceptual plan.

[Narrator] One of those experts is Dr. Brent Hughes, who, along with his colleagues, is evaluating parts of the sea otters’ former range to see if it might be suitable for the animals now.

[Brent] There's San Francisco and north, and those are the systems I personally have been studying for the last five years, to try to understand, you know, what habitats could be good for a sea otter.

Is there food there?

Is the water clean?

Are they gonna be threatened by humans in some way?

But on the flip side of it, too, is asking this question, well what would the sea otter do to these ecosystems?

Can they rebuild kelp forest?

Can they stabilize salt marshes?

Can they support seagrasses?

[Narrator] The first place Brent and his colleagues evaluated was San Francisco Bay, which was once home to around 10,000 sea otters.

Using field data and mathematical modeling, Brent and his colleagues determined that the area could likely support several thousand sea otters today.

[Brent] However, if you think about San Francisco Bay, it's got a lot going on there.

It could come with significant risk for the sea otter.

Next step is we moved on to what's up north, and creating more models, and trying to look at all these different systems and ask these questions of would this be good, would this be bad?

You know, what are the potential consequences?

That's part of our job is to make sure they would be going to the appropriate place where they'd have the highest chance of success.

[Lilian] And once we have that information, then we can take a few of those sites and really do a deep dive into the socioeconomics.

And in doing so, we'll be talking to those communities, and we'll be asking people, you know, what are the effects?

Do we have it right?

And help us come up with a plan to potentially mitigate those effects.

We've heard a lot of support, and we've heard a lot of concern, by specific people in specific areas about what could potentially happen if sea otters were reintroduced there.

[Brent] And they all need to be heard because especially for small communities in Northern California, you move sea otters into there, it's gonna have effects, be it good or bad.

[Narrator] Researchers say that reintroducing sea otters to parts of their former range will likely have many positive effects on ecosystems that humans depend on which are threatened by climate change.

The challenge is making sure that potential impacts are fully investigated.

[Lilian] We're at the ground floor of reintroduction consideration and we're not gonna do anything hasty or rash.

We really would like to get this right.

[Gena] For hundreds of years, coexistence between humans and wildlife meant that humans win and wildlife was out.

And so we're really trying to foster an ethic of coexistence that supports and allows both human activities and the wildlife to thrive.

[Announcer] Major funding for this program was provided by the Batchelor Foundation encouraging people to preserve and protect America’s underwater resources.

Additional funding was provided by Trish and Dan Bell and by the Parrot Family Endowment for Environmental Education.

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