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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, marine biology 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 will set out along the California coastline to spot them from the shore.
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 U.S. Geological Survey (USGS) sea-otter-research program in California. Michelle is the Sea Otter Research and Conservation coordinator for the Monterey Bay Aquarium; she also conducts graduate research for her M.S. degree 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 (very high frequency) radio 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, and so on. 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, the scientists compare it to the width of an otter's paw, which averages 5 cm. So, if it's the size of one paw, the food is rated a 1; of two paws, 2; and so on. No matter what the otter is doing, we keep the stopwatch running.
The mother appears at the surface, and Michelle begins writing. The otter has returned with a clam, one paw wide, roundish. She handles it for 6 seconds and then dips beneath the surface. 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. To develop a more precise understanding of this investment, Michelle has been investing a lot of time herself. Depending on the number of females in the study who have pups, she conducts 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, Michelle is learning when the pups stop nursing and when they begin to dive, use tools, and forage on their own.
Scientists have found that the mothers teach the tricks of their favorite trades to their young, passing on not only their specialized skills but also their specialized diets. If the mother uses tools, the pup will learn to use tools. If the mother has a penchant for crabs, the pup will develop one too. Scientists are wondering whether 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.
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 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, and diving; how deep she's diving; and what her internal body temperature is. 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 radio 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, scientists might eventually be able to determine what otters are eating simply by examining 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 sea otters' food supply.
Tim points out that the things we do near the coast impact the otters. "Pesticides, washing your car, fertilizing your lawnthese things affect the sea otter and the habitat directly," he says.
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 sewage treatmentwe'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 that 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 other specialists. Tim says there are 30 scientific professions involved in the sea-otter project. And one of the things he appreciates about the work 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."
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: sea urchins thrive, and kelp forests wither. But the sea otter is not only a keystone species; it is also a sentinel species. "It's the canary in the coal mine," says Tim.
The importance of the sea otter to its ecosystem is the reason 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 landthere are hundreds of substances being poured into the oceans," says Tim. It's not just water-borne contaminants that pose a problem. "There are dozens of interrelated factors that threaten sea otters and other marine species," he says.
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's 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 Alisha 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 handheld computer, which records the GPS coordinates; then she is able to download the information directly to her desktop computer. This information helps the research team track not only the sea otters with working implanted transmitters, but also those with transmitters that have stopped working and those 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 the researchers get to travel to study sea otters in other places 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, 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. "There's a whole team of people working to save this species; it's so interesting, and I feel that I can make a difference."
I've only been at it for one day, but I suspect that's what draws most people to this field: the opportunity to make a difference.
For more information on sea-otter studies at the USGS, visit the Sea Otter Studies Web site. To listen to a series of three podcasts featuring Tim Tinker talking about sea otters, visit the USGS CoreCast site and start with episode 65.
in this issue:
Tracking Sea Otters
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