Can Play Help Harbor Seal Pups Return to the Wild Sooner?

The Marine Mammal Center’s Harbor Seal Hospital is enrobed in fog as researcher Karli Chudeau arrives, dressed in layers of warm fleece and excited to start her 12-hour day.

It’s 6:30 a.m., an hour and a half before the harbor seals will get their first meal of the day, but a small team of animal care volunteers are already busy preparing fish buckets, formula and medications for the 65 seal pups onsite.

Karli says her “good mornings” to the crew as she puts on her boots and gloves and then heads outside, back into the cold morning air that is rife with a distinctly fishy smell. She gathers up a tangled mess of fibrous, blue artificial kelp strands and heads toward a harbor seal pool.

She checks her watch—it’s almost 6:45. She drops the spider-like tendrils into the water where they unfurl and hang vertically in the water, tethered to buoys that keep them afloat. With a click of her stopwatch, the observation period begins:

6:46 – Jhase and Juliet flop into the water and head toward the kelp with interest
6:47 – Juliet noses a buoys while Olga watches from the side of the pool
6:48 – Nicely has just woken up from a nap and peers up from inside a crate
6:49 – Olga and Nicely join Jhase and Juliet in investigating the kelp

Karli has what many would consider one of the most enviable “jobs” at The Marine Mammal Center. She’s a graduate student at California State University, San Marcos, and she’s studying the effects of enrichment in rehabilitating harbor seal pups. She wants to know whether giving these seal pups extra stimulation will help them progress more quickly toward returning to the wild.

It may seem like Karli spends a significant amount of time just watching seal pups play with toys, but Karli’s study, like all research at the Center, is rooted in solid science. Dr. Shawn Johnson, Director of Veterinary Science at the Center, and Animal Husbandry Manager Sophie Guarasci have been advising Karli on how to structure her study and consider future applications. And any final results will be peer-reviewed before being presented or published in a scientific journal.

For now, much of her time is spent making careful observations during discrete study periods. Karli is monitoring four pool areas located behind the Harbor Seal Hospital at the Center. Two are “enrichment” pools in which the seals are exposed to various toys during three 30-minute sessions per day. And two are “control” pools in which the seals are not exposed to the enrichment toys.

Karli and her research assistants use instantaneous scan sampling to make their observations, a research method that gives a standardized snapshot of typical animal behavior during an average day. They notate behavior every minute for 30 minutes and rather than make detailed behavior notes that can be subjective and time-consuming, they simply record numbers: 0 for no interaction, 1 for visual interaction, and 2 for physical interaction with the enrichment tool.

All five of the enrichment tools Karli is using in her study are meant to mimic something in the seal pups’ natural habitat or teach them a skill they’ll need to be successful in the wild. In some ways, Karli says, the enrichment tools may serve as a sort of surrogate for these orphaned pups that don’t have a mother seal to encourage them to explore their environment or learn these behaviors.

For example, Karli’s “kelp strands” are made from pieces of the fibrous curtains you might drive through in a car wash, but they simulate bull kelp, a fast-growing aquatic plant harbor seals encounter in the wild along the California coast. Karli has observed the seal pups biting, pulling and wrapping themselves in the strands during her sessions.

She also utilizes a large plastic pontoon that floats on top of the water, providing a perfect spot to haul out if a seal pup can figure out how to balance on the unstable surface. Though only some pups have mastered this maneuver, Karli says, it may give them a leg (or flipper!) up when it comes to slippery shorelines.

Perhaps the simplest of her enrichment objects, a PVC pipe connected to a water hose blows water into the pool, creating turbulence. Although it can’t truly mimic the strong currents seals will face in the open ocean, it does provide additional stimulation. She often observes seals sticking their sensitive vibrissae, or whiskers, into the water stream or simply rubbing their faces in it.

Two of Karli’s enrichment activities are meant specifically to teach the young pups how to forage for fish—a skill their mothers would have taught them in the wild. The first involves simply putting small fish into hidden pockets on the kelp strands. As the strands hang vertically in the water, the pockets rest at different heights in the water column, just as different prey can be found at different depths.

The second foraging object is modeled after an enrichment box built with the help of the UC Davis bio-engineering lab to aid the Center in assessing Agaptimoss, a blind harbor seal pup rescued in 2013. The weighted box is filled with fish and placed at the bottom of the pool. The seals must figure out how to open flaps on the box to get to the fish, all while holding their breath.

Encouraging this diving behavior is another key component in Karli’s study. Building on recent research comparing diving capabilities of rehabilitated seal pups with those in the wild, Karli hopes to look at diving behavior among her two study groups and determine whether the enrichment devices better prepare seal pups to make longer foraging dives in the wild.

Her study methods are twofold in this respect. During her observation sessions, she places video cameras overhead, allowing her to record the seals’ movements and to later document the amount of time each animal spent underwater. But she’s also using blood samples from admit and release exams to help her gauge dive fitness.

Harbor seal pups begin diving soon after birth, which helps stimulate the development of larger red blood cells that can hold more oxygen, allowing the seals to dive deeper and longer over time. By measuring the blood oxygen levels in the seal pups that had more practice diving and comparing it to her control group, Karli may be able to see whether the enrichment tools helped better prepare the pups to forage once they are released.

Karli is also hoping to measure stress levels between the two groups to see whether the enrichment tools help reduce the stress of being in rehabilitation and away from familiar surroundings. This aspect of her study also involves a two-pronged approach.

Every day, Karli and her research assistants conduct two 30-minute observation sessions in each of the four pens focused solely on looking for what they call “stereotypical” behaviors, such as suckling on other seals or objects, chewing their own flippers, scratching themselves and swimming in repeated patterns. Karli likens these self-soothing behaviors to human habits such as biting your fingernails or twirling your hair.

She wants to know whether the enrichment time gives the seal pups enough physical and mental stimulation to reduce the need for these nervous tics, so she monitors both the enrichment groups and her control groups and notates every time one of these behaviors is observed.

To further assess the animals’ stress levels, she collects fecal samples from each of the seals to test cortisol levels. This hormone will be present in higher levels in an animal that is more stressed, and can even impair an animal’s immune system. If she finds that cortisol levels are higher in her control group, it could suggest that the enrichment time helps reduce stress for pups in rehabilitation settings.

Throughout the Center’s harbor seal pup season this year, Karli has been gathering data on how all of the seals in her study are progressing through their recovery. To reduce variables, she is excluding any pups suffering from medical issues beyond our most common diagnoses: malnutrition and maternal separation, or being separated from mom before weaning off her milk.

As Karli looks through the patient charts, she is notating when the seals in her study graduate through various stages of eating fish. At first, harbor seal pups are fed a special milk formula similar to what they would get from their mothers. But as their teeth grow in, animal care volunteers begin teaching them how to swallow fish whole—first by hand-feeding them out of the water on the pen floor, and then in the shallow end of the pool.

Eventually the seal pups learn how to catch fish on their own and compete with their pen-mates to grab fish floating freely in the pool. Karli is keen to find out whether the enrichment tools help shorten the learning curve, reducing the time the pups need to be hand-fed. The faster they can progress to eating well on their own, the faster they’ll be able to return to their ocean home.

“I hope these enrichment sessions are able to give these orphaned pups the tools they need to succeed,” Karli says. 

Seeing them ready to return to the wild healthy and strong is like a proud mom moment for me.

Though she won’t have final results until after all of the harbor seal pups are released and she is able to analyze her data, Karli and the veterinary experts at the Center are hopeful that this research will help inform future animal care practices both here and at other rehabilitation centers.

Researchers like Karli are working hard to ensure orphaned harbor seals have the very best chance of survival, but it is supporters like you who make these second chances possible. You can make a real difference for pups like Jhase and Juliet with your gift today. 

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