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Sea Otter Awareness Week, Sept 21 - 27, 2008

A Day in the Life of a Marine Biologist: Tracking Sea Otters off the California Coast

By Tania Larson

As I arrive at the marina in Monterey Bay, the sky is the dull gray of early morning. A thin fog floats over calm waters, a horizon of glass interrupted by protruding kelp leaves, the occasional emerging head of a sea lion, and an otter floating effortlessly on its back. But the sea gulls are starting to call from over head, a few sea lions hauled out on the pier are beginning to bark at each other, and the engine of a whale-watching boat is just rumbling to life in the distance.

Both the marine and the human world are waking up, and our small crew needs to hit the water soon if we want to be at the table as the sea otters enjoy their breakfast.

This is my day to live the life of a marine biologist studying sea otters, and I couldn’t be more excited. If you love the water, are enthralled by marine mammals, and want a job that makes a difference — this is working the dream.

For the morning, I am heading out in a boat to track and observe sea otters in the bay. In the afternoon, I am setting out along the California coastline to spot them from the shore.

Researchers on a boat
Sea otter researchers Michelle Staedler, Monterey Bay Aquarium, and Tim Tinker, USGS, work together to locate sea otters in their study project.

I meet up with researchers Tim Tinker and Michelle Staedler, and we immediately begin to load the boat. Snacks, logbooks, life jackets, and a jumble of tracking equipment are all stored and secured. Tim is lead scientist for the USGS sea otter research program in California. Michelle is the Sea Otter Research and Conservation coordinator for the Monterey Bay Aquarium. She also conducts research as a master’s degree student at the University of California, Santa Cruz. 

And then, we’re off on the chase.

We’re not looking for just any otter. We hope to find a specific few that the team has been following as part of a study examining how the otters eat and how they raise and train their pups.

Tim drives the boat, while Michelle holds out a VHF receiver, waiting for the beep that will tell her that one of the study animals is in the vicinity. We haven’t gone far, when Michelle has located 6-068 so called because that is the otter’s radio transmitter frequency. As they suspected, this mother otter is foraging in the local marina.

Like humans, when it comes to dining, each otter has its own favorite dives. One may prefer the crabs and clams at the marina. Another, the delectable sea urchins from a more private spot up the coast.

Also like humans, some sea otters use tools when they eat. In areas where otters have to compete with each other for limited food, individuals tend to specialize in particular foraging skills. One otter may focus on finding abalones, another on using tools to crack crab shells. These variations in their foraging techniques help the species to survive.

Our job today is to watch and record the mother otter’s behavior, particularly her eating habits: how long she dives, what she brings back to the surface, whether she shares it with her pup, etc. The logbook is precise and detailed.

For each dive, Michelle fills in a grid of information: dive time; successful dive (yes or no for returning with food); types, quantities, and sizes of food; handling time of the food; and full surface time. To measure the size of the food, they compare it to the width of an otter’s paw, which on average is 5 centimeters. So if it is the size of one paw, the food is rated a one, of two paws, two, and so forth.

No matter what the otter is doing, we keep the stopwatch running.

The mother appears at the surface, and Michelle begins scribbling. The otter has returned with a clam, one paw width, roundish. She handles it for 6 seconds, and then dips beneath the surface.

Sea otter appearing in the water.
A sea otter swims in Monterey Bay, California.

When she reappears, she has a collection of food. Otters will often use their abdomen as a makeshift serving tray, and they can pile it high with goodies. She chomps down on a fat innkeeper worm. When she’s finished, she offers a morsel of something to the pup. The pup refuses it. Again, she offers it to the pup, and again the pup declines. She dives back down to hunt for tastier fare.

“She’s keeping the good stuff for herself,” Michelle comments. “Whatever she just offered the pup, neither of them wanted to eat.”

Michelle records all of these details to help scientists understand how much the individual mothers invest in their pups, how much energy they expend in finding food, and whether different investments, energy expenditures, and nutrition affect the success rates for the mothers. Sharing food is considered a big part of the mother’s “investment” in the pup.

In order to develop a more precise understanding about this investment, Michelle has been investing a lot of time herself. Depending on the number of females in the study who have pups, she does anywhere from two to seven activity budgets per week, watching for all the big firsts for the young otters. Each budget is a 6-hour session of collecting continuous data on a mom and pup pair from shore. Over the length of the study, she is learning when the pups stop nursing and when they begin to dive, to use tools, and to forage on their own.

Scientists have found that the mothers teach the tricks of their favorite trades to their young, passing on not only the specialized skills, but their specialized diets. If the mother uses tools, the pup will use tools. If the mother has a penchant for crabs, the pup will develop one too.

Scientists are wondering if these individualized diets are the secret to success for some otters and the road to ruin for others. They hope that seeing where and what otters eat will shed some light on the recent rise in the mortality rate of California sea otters.

Sea otters are listed as threatened under the Endangered Species Act, and the goal of the science is recovery and conservation of the species.

Sea otter dining on crab meat.
A sea otter dines on crabmeat in Monterey Bay, California.

Number 6-068 pops back to the surface with a cancer crab. Michelle notes the dive time, and begins counting the handling time for this particular fare.

There is, of course, a reason for this stopwatch obsession. Recording the times of the activities will help the scientists to align the data from their observations with data from an instrument that researchers implanted in the otter’s abdomen at the beginning of the study.

This time-depth recorder provides a detailed look into the life of the otter: when she’s eating, resting, diving, how deep she’s diving, and her internal body temperature. With these implanted devices, the researchers are able to follow an otter’s every move for 1 to 2 years. A second device, the VHF transmitter, allows scientists to locate the animals by radio telemetry for 3 to 5 years.

From these recorders, the team will get data on thousands of foraging dives. And with all the observational and electronic data lined up according to Michelle’s carefully noted times, in the future, scientists might be able to determine what the otters are eating simply by the electronic data on where, how long, and how deep they are diving.

By comparing this information with survival notes, including necropsy and pathology data, the researchers hope to track not only food patterns, but also sources of contamination in their food supply.

Tim points out that the things we do near the coast impact the otters. “Pesticides, washing your car, fertilizing your lawn — these things affect the sea otter and the habitat directly,” says Tim.

The physical elements of the landscape that once filtered pathogens out of the water have largely disappeared, and sea otters are facing ever higher levels of contamination in their environment.

“We have changed the water-flow patterns with runoff, storm sewers, agriculture, loss of wetlands,” says Tim, “nature’s sewer treatment — we’ve changed that drastically. Now water flows over the ground directly to the ocean.”

Sea otters are turning up with diseases normally found in cats and opossums. Researchers suspect the sea otters are picking up these pathogens not from each other, but by foraging in areas with agricultural or urban runoff. But scientists need more information.

This is a task that is beyond just marine biologists. To see the big picture of what the sea otters are facing, the team needs ecologists, pathologists, toxicologists, epidemiologists, and others. Tim says there are 30 scientific professions involved in the sea otter project. And one of the things he appreciates about the field is that it’s not about competition, but collaboration. They have spent 10 years building an alliance, and Tim says they now have a loose, ever growing network of partners.

“There is an atmosphere of trust,” Tim says. “We need to recognize how important that is and make sure to maintain it, to train new people that this is not a competitive endeavor. We share data and results.”

Studying sea otters from the shore.
USGS wildlife biologist Alisha Kage looks through a telescope to help her locate and identify tagged sea otters, then records the otter's location for a study aimed at learning more about the species.
View of kelp forest from above water.
Kelp forests are often called the rainforest of the sea. They support wide varieties of marine life. Sea otters are both a sentinal and a keystone species for the health of kelp forests.

Part of the reason for this trust and teamwork is the concern for the animal at the center of the project. The sea otter is a keystone species. Without sea otters, there is a dramatic shift in the ecosystem. Without sea otters, sea urchins thrive, and kelp forests wither.

But the sea otter is not only a keystone species; it is also a sentinel species. “It is the canary in the coal mine,” says Tim.

That’s why there’s so much collaboration among so many specialists.

“We’re trying to take more than a single species approach to our research,” he says. “The things that threaten otters threaten the whole ecosystem.”

“Human-induced impacts on kelp forests, fisheries, contaminants that come from the land — there are hundreds of substances being pored into the oceans,” says Tim. And it’s not just water-borne contaminants that pose a problem. “There are dozens of inter-related factors that threaten sea otters and other marine species,” says Tim.

The good news is that despite a higher rate of mortality in recent years, the overall trend in the number of California sea otters is a growing population. The goal is to keep it that way and to eventually be able to delist the species.

Just as the sun is beginning to break through the fog and the cloud cover, it is time for Michelle and Tim to head back, but the day holds one more outdoor adventure for me.

Back on land, I meet up with Alisha Kage, a USGS wildlife biologist and sea otter researcher, for a few hours of tracking the sea otters from shore.

Alisha drives along the sunny California coastline, and periodically we hop out and hike along the edge of the cliffs to look out and locate tagged otters using a VHF receiver and a telescope. We scan the surface for sea otters, and then she zooms in on them with the telescope to identify their tags.

She’s happy that these days she doesn’t have to do it all by hand. She simply enters the data into a hand-held computer, and it records the GPS coordinates. Then she is able to download the information directly to her desktop computer. This information helps the research team keep track not only of the otters with working implanted transmitters, but those with transmitters that have stopped working and sea otters that have been tagged for other studies.

Like Michelle, Alisha often spends long days in the field.

“With driving, I do 12-hour field days,” says Alisha, “but I just love being in the field so much it doesn’t bother me.”

Walking along the sunny California coast, I have to agree that it’s hard to complain. But Alisha adds that the perks don’t end here. Sometimes, they get to travel to study sea otters in other locations and compare notes with other scientists.

“When you’re in the field somewhere like Alaska, you just feel so lucky to do what you do,” she says.

And like Tim, Alisha comments on the network of other scientists from the USGS, the University of California at Santa Cruz, and the Monterey Bay Aquarium who are all working together for the sake of the species.

“I always wanted to work on endangered species,” she says, “to make a difference. And I feel like there is a whole team of people working to save this species. It’s so interesting, and I feel like I can make a difference.”

“Did that sound sappy?” she asks. “I feel like that sounded kind of sappy. I really meant it, though.”

I’ve only been at it for one day, but I suspect that that is what draws most people to this field: the desire to not just say I can make a difference, but the opportunity to really mean it.

For more information on sea otter studies at the USGS, visit the Sea Otter Studies Web site.

To listen to a podcast of Tim Tinker talking about sea otters, visit the USGS CoreCast site and start with episode 65.


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