(serene music) (seals grunting softly) - [Narrator] Along the Pacific Coast of North America, northern elephant seals congregate on the shores of their home colonies.

(gentle instrumental music) Spending most of their lives at sea, these massive marine mammals return to the safety of the beach on regular cycles to mate, nurse pups, and shed their fur coats.

Though usually seen napping lazily amongst isolated sand dunes, the seals' breezy afternoons are just a small part of their remarkable story.

(gentle instrumental music) - [Allison] When we see them on the beach, they're kind of lumbering around or they're galumphing.

And I think that they're amazing creatures on land, but that's really kind of the weirdest place to see them.

(seals grunting) (gentle instrumental music) - [Dan] Elephant seals are extreme at everything they do.

They're extreme divers.

They're the deepest longest diving sea lion or seal.

They're the most extreme example of what we call a capital breeder, where they store up all the energy they need and then come and fast on the beach.

Everything about them is just extreme.

They're an animal athlete.

They're an Olympian in all aspects of their biology.

(gentle music) - [Narrator] Once prized for their thick blubber, northern elephant seals were nearly hunted to extinction in the late 1800s.

When the last surviving colony of fewer than 20 seals was discovered on Guadalupe Island, the Mexican government took the lead in their protection.

Today more than 350,000 of their descendants thrive on islands stretching from Baja to British Columbia.

While the largest colony resides in the Channel Islands, the first mainland colony and the most studied is found at Ano Nuevo State Park in Northern California.

(seals grunting) (waves crashing) - [Roxanne] At Ano Nuevo right now we have about 10,000 unique seals that call that beach their home.

At any given time, there are about 2,000, 3,000, 4,000 seals on the beach, and about 20% of those have flipper tags.

And those are the seals that we're keeping individual track of, so we can know things like how often they survive, how old they are, and whether they're reproductively successful in a given year.

- [Narrator] Researchers from the nearby University of California, Santa Cruz, have collaborated with the state park for nearly six decades to study these impressive marine mammals.

- [Patrick] Elephant seals are just wonderful research partners, in part because they're very amenable to people getting fairly close to them.

And not only that, the accessibility part is key, but also the reliability.

So they'll return to the same area again and again.

(gentle music) - [Narrator] In addition, the foraging range of Ano Nuevo's seals covers more than one million cubic miles of the North Pacific.

This provides an unparalleled opportunity to collect data on a largely understudied, yet biologically rich region of the deep ocean.

(gentle instrumental music) - [Patrick] With every elephant seal dive, we're getting information about the temperature profile of the water.

In some cases, we're getting chlorophyll content of the water.

We're getting information about prey consumption.

So, we're getting this window into that deep environment that we could not get using other tools available.

- [Narrator] Now, with nearly 60 years of consistent data collection, a project passed down through an unbroken chain of generations of seals and researchers, scientists can ask big questions about the health of the ocean, gaining insights into changes that would otherwise be impossible to measure.

How are the elephant seals of Ano Nuevo contributing to oceanographic research today?

And what can they tell us about the future of the deep sea?

(dramatic theme music) - [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 the Parrot Family Endowment for Environmental Education.

(bright music) (water crashing) - [Narrator] Just a short drive south of San Francisco, where the Pacific Ocean meets California's rugged shores, lies the hidden gem of Ano Nuevo.

When the state park was established in 1958, its sand dunes had yet to become a now iconic sanctuary for this very special population of northern elephant seals.

- These elephant seals are actually a pretty new phenomenon here.

The first pup was born on Ano Nuevo Island in 1965.

The first pup on the mainland was not until 1975.

(upbeat instrumental music) - [Narrator] For nearly 50 years, Ano Nuevo State Park has offered guided tours for the public to see the elephant seals.

More than 100,000 people visit annually, with nearly 200 volunteer docents leading the way.

In winter, seals can be seen mating, giving birth, and nursing their pups.

In spring, as females return from their first of two annual migrations, they can be seen molting, or shedding their previous year's fur coat.

- So the access to the elephant seals is incredible.

We can get within 25 feet of these 4,000 pound animals.

And that way you can get out and see the seals with a docent naturalist, but also it protects the animals from human disturbance.

(gentle music) - [Narrator] Alongside public tours and interpretative programs, the state park has fostered a long-standing relationship with the overlapping Ano Nuevo Reserve established by the University of California.

- Ano Nuevo is a pretty busy place when it comes to both research and teaching.

So, we have researchers going out nearly every day of the breeding and molting seasons.

Sometimes multiple teams going out each day and just a little bit less activity during the rest of the year.

(gentle music) - It's a great relationship.

It's symbiotic.

You know, we help support access to the park.

It's kind of a living lab.

It's really an excellent program that benefits us, them, and the general public.

(gentle music) - [Narrator] Down the coast, the University of California, Santa Cruz sits at the center of northern elephant seal science.

This world-class research program was built over 60 years by three generations of scientists.

(gentle music) Professor Burney LeBoeuf began this long-term study of Ano Nuevo's seals on the beach in the late 1960s.

In the 1990s, Professor Dan Costa advanced this research, pioneering satellite tagging and using remote data loggers to study seal behavior at sea.

- It's a trans-generational program, that there's really three investigators now that have been working on this system since the late 1960s, which is pretty incredible.

- Give me slightly more detail.

- [Narrator] The third principal investigator in this seal science family tree is Roxanne Beltran, a UC Santa Cruz professor focused on expanding our ecological understanding of these elephant seals and what they can reveal about the health of the Northern Pacific Ocean ecosystem.

- One of the cool things about this program is there's been so many generations of seals and so many generations of humans.

And so, I get to come in and work from there and be able to expand to ask different or broader or finer scale questions than we have ever been able to before.

(gentle music) (people speaking faintly) - [Narrator] At the heart of this program is a long-term flipper tagging effort, where research teams carefully capture, tag, and release weaned seals each year, then track them through their lives.

This mark and recapture method has collected data on more than 50,000 individual elephant seals.

A key component of this is the re-sight process.

This collaborative effort takes place nearly 300 days a year at Ano Nuevo.

- During the re-sighting process, we grab all of our gear, and then we approach the animals from a safe distance.

Once we see their flipper tag, we write down what it is, more data on the animal, like the age or sex, if it's a male or female, and then if she has a pup or not, if so for our adult females, and then record that into our long-term database.

(gentle music) - [Narrator] During re-sights, researchers also mark the seals with their alpha-numeric flipper tag numbers to make them more easily visible.

These marks are applied using a marking pad with hair dye or bleach ensuring no harm comes to the animal or the researcher.

Over time, the marks are lost to molting, requiring re-marking each year.

- Re-sights are amazing because you can truly learn so many things just from seeing who comes back at what times of year.

One surprising thing is just how different all of their personalities are.

That you really get to know individuals spending a lot of time with them.

- [Narrator] The vast majority of elephant seals tagged for the long-term mark recapture program are selected within their first few months of life.

- When an elephant seal is born, it is a pup with its mom for about a month.

And during that time, the mom gives the pup all of this milk, this really energy-dense milk that causes pups to gain a lot of weight very quickly.

- [Narrator] These weaned pups or weanlings grow to nearly 200 to 300 pounds, building fat stores they will rely on while their mothers head back out to sea for a short foraging migration in the spring.

- [Natalie] And so these weanlings hang out on the beach for a few months, and during this time, they build up muscle.

They learn how to dive.

They practice holding their breath, and our research team goes out and they locate specific weanlings.

And they will weigh these weanlings, and they will also attach flipper tags to these animals.

(people speaking faintly) - [Narrator] Developed and refined over decades, the weanling weighing process is carried out with great care for the young pups.

Researchers are especially cautious around their still developing front flippers, with only the most experienced team members handling the weanlings directly.

They also take length and girth measurements, collect samples of the original fur, known as lanugo, and note how much has molted.

Two tags bearing the seals' unique alphanumeric codes are attached to their flippers, ensuring the placement does not hinder movement.

This process is crucial to the long-term elephant seal study, forming the foundation for each seal's re-sight history while also offering insights into the success of each weanling's lineage.

- Collecting the weight of the animal and the lengths of the animal is really important in informing us of how successful mom was foraging while she was pregnant.

A larger weanling may reflect a more successful foraging trip.

And that mass measurement can also play into survival rates of seals and provide us some insight into how larger seals may have a higher likelihood of surviving versus smaller seals.

(bright music) - [Narrator] Over the course of a month, the team will weigh and tag 200 of Ano Nuevo's weanlings.

About half of these will be from known mothers, meaning the pup's lineage can be verified through its mother's documented history.

These known mom pups are a high priority for weighing because they allow researchers to establish generational linkages.

- One of the things we're super excited about is being able to create this pedigree of elephant seals, where we have grandmas and moms and daughters.

And in order to do that, we have to link the pups to the moms when they're both there for the breeding season.

So, the fact that we've been able to do that with seven generations of seals over this whole research program and that we have known mom pup combinations for about a hundred seal pairs per year for 60 years is a pretty incredible data set.

(seal grunting) - That is, that is, beautiful.

(light dramatic music) - [Narrator] Back at UC Santa Cruz, all of the information collected is entered into a massive database spanning six decades, including written logs from the pre-digital era.

This treasure trove of information, painstakingly gathered day after day, year after year by hundreds of researchers is an invaluable resource that enables insights not possible over shorter time spans.

- The long-term data here is truly a gold mine.

We have the histories of so many of these seal's lives from the time they were born until the time that they died, and every pup that they had in between.

- Having a long-term data set is extremely important, in part because of the questions we can address with those data, but also because it is a very rare thing.

Most funding cycles are three or four years, and elephant seals can live up to 23 years.

So, if we want to ask big questions about elephant seals in the ocean, about climate change, it really takes a long data set to be able to address those questions.

(light dramatic music) - [Narrator] While researchers have collected shore side data since the 1960s, recent advancements in remote tracking instruments, like bio-loggers and satellite tags, have enabled them to expand their knowledge.

They now track the seals beyond the beach and into the depths of the North Pacific Ocean.

- Since 2004, we've been measuring 40 animals every year that we're measuring how deep they dive and where they go.

And so now we have data on how hard they're working, where they're going, and how where they're going in the ocean is changing.

So, our elephant seals are collaborators in terms of the ocean observing.

It's one more piece that tells us how the ocean environment is changing.

(gentle music) - [Narrator] As bio-logging and satellite technologies have evolved, researchers at UC Santa Cruz have also refined their methods to safely and effectively deploy these instruments on the seals.

- Deploying instruments on wild animals is always a little bit of an adventure.

The first thing you have to do is capture the animal and make sure that you can handle it safely.

And for us with an elephant seal that weighs three or four or five-hundred kilograms and are much bigger than we are, that means sedating the animal first, so that we can manage it safely.

The protocols for sedating elephant seals in particular are very, very well tested.

In fact, one of the reasons we sedate them, aside from the human safety component, is that it is less stressful for the animals.

- [Narrator] While the seal is sedated, the team takes measurements, weighs the animal, and uses hand-held ultrasound to measure blubber depth.

Bio-logger tags are affixed with a quick setting epoxy to the seal's fur, keeping the tag securely in place while allowing for future retrieval.

Studies have been conducted to confirm these tags do not impact the seal's natural behavior at sea.

(gentle music) - We do think about that because we want data that reflect what elephant seals do.

We don't want data that is affected by our handling of the animals.

So, we really do think about how to minimize the impact of our studies, both ethically, but also for the quality of our data.

It's paramount.

(seal grunts) (gentle music) (person shouts) (seal grunting) - Each of the seals that we're tracking right now has a satellite linked transmitter on the head that has a little antenna.

And so, we actually put it on the head so that antenna will break the surface of the water and be able to communicate to satellites.

And so we can sit at our computers and see where each of those seals is every single day, which is pretty amazing.

- When they're going out to sea, basically, the females will beeline it out into the middle of the Northeast Pacific.

They have some of the most straight trajectories of any marine animal.

They go out there on the short migration, which is the post breeding migration, and then back.

They don't spend much time out there.

And then during the post molt migration, they will travel out to some of these areas and then spend months of time feeding out there.

(gentle music) - [Narrator] When it's time for these females to return to Ano Nuevo, they not only swim directly back but also time their journey with remarkable precision, ensuring they give birth within the safety of the beach.

This ability to navigate thousands of miles and synchronize their natural cycles has long puzzled researchers.

- We have individuals that do the same trip year after year.

They know where they are in the ocean.

How do they do that?

You look at the track when they return, it's a beeline back to Ano Nuevo.

It's a tiny target, and no midcourse correction.

They just come right back.

(gentle music) - [Narrator] The seals' trajectory and pacing are so precise that researchers can use live satellite data to closely estimate their return dates.

When the animals reach the shore, the team uses a VHF receiver to triangulate their exact position based on signals from an additional radio tag.

- [Rachel] So once the animal's back on shore and we've located it, so we know exactly where it is, we will then re-sedate it in order to remove all the tags, which is necessary to get all the data.

And then we repeat all the measurements that we did at the deployment, which includes lengths, girths, blubber depths, weight, and that will tell us how successful the animal was while they were at sea.

So how good a job did they do foraging and how does that relate to where they went in the ocean?

- [Narrator] Once the animal is released, the only trace of their data gathering mission is a small patch of epoxy and mesh.

- [Rachel] That is just attached to the animal's fur.

And just like your cats and dogs, these animals shed their fur and as soon as that fur comes off, the whole patch comes off, and there's nothing that stays on the animal long term.

(gentle music) (serene music) - [Narrator] Over the past 30 years, a total of nearly 1,000 seals have carried data loggers out to sea, providing a wealth of information about their behavior and the dynamics of the deep North Pacific leading to remarkable insights.

In addition to their long migrations, the team discovered that the seals spend most of their time about 1500 feet below the surface, in the dark depths of the ocean.

- So, elephant seals when they're at sea, they're typically diving about 20 to 25 minutes underwater and spend about two to three minutes on the surface, and they will keep that dive pattern up for the entire trip to sea.

They very rarely will come to the surface and rest.

(gentle music) - [Narrator] Decades of studying seal dive profiles have revealed distinct patterns.

Dives with jagged edges were confirmed by Japanese colleagues to be feeding dives.

Drift profiles showing a seal either slowly sinking or floating up based on its buoyancy were found to be sleeping dives.

- So, we think that they're feeding, feeding, feeding, and then they got a full belly and they go down to depth.

Go to sleep, and then drift.

Then wake up and come up.

And so, they're taking cat naps.

And they tend to follow after a big period of feeding.

- [Narrator] Tiny camera tags revealed that female elephant seals primarily feed on small fish, requiring them to constantly forage while diving.

This continuous feeding is vital for accumulating energy stored as blubber to sustain them while fasting back on shore.

- To give you a sense, the adult females have to eat on average a thousand fish every day in order to be successful.

So, we like to say it's like they're snacking on potato chips as they're diving because they are just constantly eating.

They just snack throughout the entire day.

(upbeat music) - [Narrator] The seals also carry instruments to measure ocean conditions like salinity, temperature, and dissolved oxygen.

And with the addition of acoustic tags now recording ocean sounds wherever they go, they have become true ocean observers.

In a recent study, researchers used the long-term data set on weanling weights, which is a reflection of their mother's foraging success that year to extrapolate how the health of fish stocks in the deep North Pacific varies over time.

This, in turn provides a bellwether for ocean conditions overall, turning the seals into ocean sentinels.

- The seals have always been able to measure the physical conditions, but now we can put this extra piece of the biological conditions into that puzzle.

And what we're able to show is that in years where the seals are finding a lot of food they're gaining a lot of mass, and those seals are producing more pups that are bigger, that are more likely to produce pups of their own.

And the population persistence is much more likely to be true.

And so, there's a really critical link all the way from physical oceanographic conditions like the temperature of the ocean and the sea surface height, all the way up to the demographic success of these top predators, and that provides a lot of really useful information for other species as well, so species like whales and seabirds that are more difficult to study but that rely on a lot of the same marine resources.

(upbeat music) - [Narrator] Researchers are also actively developing less invasive methods to collect seal weights across the entire colony at once, potentially extending their understanding of ocean health with a single drone flight.

- If we can fly a drone over all the seals and estimate the mass and compare that from year to year, we don't have to handle the animals.

We can do that with a larger sample size.

It's a lot easier for us.

And so, this provides us with a unique opportunity to do the calibration that could then be applicable to other species.

(waves crashing) (gentle music) (gentle music) (waves splashing) - [Narrator] These rare glimpses into the deep ocean and elephant seal behavior have only been made possible through the combined efforts of generations of dedicated researchers, their seal collaborators, and the staff and volunteer docents at Ano Nuevo State Park, whose commitment to protection and education ensures the sanctity of the beaches these ocean sentinels call home.

- It's impossible to go to Ano Nuevo and leave and not feel inspired by the seals.

And one of the best parts of our job is being able to share that joy with members of the public.

- The state park is really critical, a, for protecting the seals, but also the ability for the public to go and get really...

Fantastic interpretation is unmatched.

The bulk of it really is credit to the state park and the docent program there.

- People have worked pretty hard on protecting this swath of land, and it's nice that so many people get to enjoy it.

It's a labor of love.

(bright orchestral music) (seals grunting) (light dramatic music) (seals grunting) (light dramatic music) (seals grunting softly) - [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 the Parrot Family Endowment for Environmental Education.

(bright music)