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Harbor Seal Update: Float Research, Whiskers for Survival, and Boating Etiquette

Alameda Point harbor seal float inspires research at New York Aquarium

The harbor seal float at Alameda Point has been wildly successful. It started out as an experiment. Now it’s a model being studied at the New York Aquarium.

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Harbor seals on the Alameda Point float on March 10, 2023. Ferry maintenance facility is in the background. The Bay Trail runs along the shoreline to the right. Photo Richard Bangert.

In July 2022, the Wildlife Conservation Society’s New York Aquarium installed a float in an exhibit modeled after the float at Alameda Point. The research project was initiated by aquarium keeper Payden Sra as part of her work toward a graduate degree. Studying haul-out behavior of harbor seals in a controlled setting “can better advise conservation actions for the growing wild seal populations managed by local officials on the East Coast,” Sra wrote in the description of her study. “While once a rare sight, it is increasingly common to see seals in New York.”

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Visitor education panel at the Sea Cliffs exhibit at the New York Aquarium. Featured photo shows the Alameda Point harbor seal float. Photo Wildlife Conservation Society/The New York Aquarium.

Harbor seals spend anywhere from a third to half of their day out of the water in order to warm up and rest. They also typically give birth on land, although they can give birth in the water.

Both the continuing pressure from people using shoreline areas and rising sea level present challenges for the future well-being of harbor seals.

Building on the work already done on the wild population of Pacific seals at Alameda Point, “one can better understand if Atlantic harbor seals on the East Coast have alternative haul out preferences,” aquarium keeper Sra said. “This research is likely to be important in understanding how successful undisturbed man-made structures can be created off the beaches specific to the East Coast and, ultimately, aid in the survival of wild harbor seals.”

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Harbor seals in marshland at Mowry Slough in 2015, which is native habitat where birthing typically takes place. Sea level rise will one day eliminate coastal haul out sites like this. Photo Richard Bangert.

The “Sea Cliffs” exhibit educational panel features the banner photo used on the Alameda Point Harbor Seal Monitors Facebook page. The behavior of six harbor seals in the exhibit has been systematically monitored with cameras. The younger seals can be seen using the aquarium’s float in an October 2022 Instagram video clip. The access slope on the float is steeper than the one at Alameda Point, and the younger seals have taken to using the float as a play structure, sometimes leaping onto the high side and sliding across the float and down the ramp.

Alameda Point float no longer an experiment

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Harbor seals warming up and napping on a cold January 6, 2023, day, with one seal in water thinking about joining them. Photo Richard Bangert.

When the San Francisco Bay Conservation and Development Commission (BCDC) issued its permit in 2015 to allow the deployment of a 500-square-foot floating structure in the Alameda Point harbor, it required proof of effectiveness. The Water Emergency Transportation Authority (WETA), also known as San Francisco Bay Ferry, built the harbor seal float as part of its construction of the nearby ferry maintenance facility.

At the time of deployment in June 2016, it was the only known floating structure in the world built specifically for harbor seals and, therefore, considered experimental by BCDC. The permit’s Effectiveness Evaluation clause stated, “If after a period of three (3) years, the replacement haul-out is proving to not be effective, WETA will coordinate with BCDC to evaluate options for removal of the seal haul-out.”

Volunteers with Alameda Point Harbor Seal Monitors began keeping daily counts of the seals, who quickly took a liking to the float. Six months later on January 5, 2017, the float was packed with 70 seals. On December 14, 2020, there were 86 seals crammed onto the float, some of whom were likely attracted by strong winter herring spawning in the vicinity. Needless to say, it’s no longer an experiment.

Cool science fact about seal whiskers

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Harbor seal whiskers are easy to see in this March 17, 2023, photo of seals moving about on the float. Photo Richard Bangert.

The 2022 harmful algae bloom in San Francisco Bay that began near Alameda and killed thousands of fish around the Bay did not appear to have affected the harbor seals. Based on photographic monitoring they remained healthy-looking throughout the fish die-off.

It is unclear whether the seals have natural immunity and are unaffected by the toxin in the harmful algae. What is clear, however, is that they have the ability to forage and find healthy food at any depth of the Bay, even in total darkness. The secret is in their whiskers, a highly evolved part of their bodies capable of tracking wave movements of prey.

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Tour led by a Crab Cove naturalist in December 2021 stops to observe the harbor seals. Photo Richard Bangert.

“Mammals generally have regularly shaped, round whiskers. But nearly all seal species have whiskers that are irregular and wavy,” James McNish writes in “How seals’ whiskers help them hunt underwater” on the Natural History Museum of London website. “The irregular shape of the whisker holds it steady as the seal swims. The whisker only vibrates in response to hydrodynamic trails.”

Seals, sea lions, fur seals, and walruses all have whiskers on the sides of their mouths. “In the 1970s, researchers discovered that these specialized hairs are used to detect water movements,” Mikołaj Zybała writes in “Seals “See” And Hunt Fish With Their Whiskers” on the Whale Scientists website. “As the seal swims around, it passes through multiple hydrodynamic trails left from fish that swam in the area.” The whiskers are essentially a tracking device that allows them to not only find prey but also follow their fellow seals.

No watercraft by the float

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Motorboat coming way too close to the harbor seal float for photo-taking on February 25, 2023. Photo Richard Bangert.

Everyone loves Alameda’s harbor seals. But plowing straight up to the float on any watercraft is not cool. Recently, a boat entered the harbor and headed straight for the harbor seal float so the passenger could take close-up photos. The approaching boat caused all of the seals to raise their heads, a clear sign of alarm. Other instances of bad behavior have involved kayakers paddling directly at the float, causing the seals to panic and bail out into the water. The Marine Mammal Protection Act prohibits knowingly causing harbor seals to leave a resting place.

When the seals see watercraft approaching with paddles swinging in the air, it can look like trouble is coming, perhaps due to an evolved instinct over eons from having been hunted for their fur. The best practice is to not paddle directly at the float, keep the paddle action on the low key, and if you see the seals raising their heads, it’s not because they are glad to see you—it means you are too close.

Contributing writer Richard Bangert posts stories and photos about environmental issues on his blog Alameda Point Environmental Report, His writing is collected at

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