On a recent Friday, as the morning clouds burned off over the San Francisco Bay, Bill Miller spotted an unexpected swimmer, heading away from Angel Island.
At first, he thought it was a seal or sea lion, paddling across the milelong Raccoon Strait between Angel Island and Tiburon.
“Then I realized it was a coyote,” said Miller, a California State Parks environmental scientist. “It was pretty exciting.”
Miller said he was running late that morning and almost missed his boat ride from Tiburon to check game cameras on Angel Island, as part of a study on animal population, diet and genetic relatedness.
“I’m going out there to look for coyotes on camera, and then here just to see one, swimming, it was pretty fun,” Miller said.
As the Parks’ boat motored past, Miller expressed concern for the coyote, with its pointy snout and ears lifted above the water, and wondered aloud if they should help it. Ultimately, staff decided not to interfere.
“I think I made the comment ‘We’ll give you a ride, buddy,’” Miller said. “But it was fine on its own.”
After making it about a quarter of a mile away, the coyote turned around and swam back into Angel Island’s Ayala Cove, before climbing the seawall and returning to shore.
Park interpreter Casey Dexter-Lee has been living and working on Angel Island for 25 years. She said scientists aren’t sure what motivates coyotes to swim in the bay.
“It is an uncommon sight,” she said. “For the most part, the coyotes are just taking short swims and either returning back to Angel Island — or if they’re starting on the Tiburon side, turning back to Tiburon. It’s very rare for one to go all the way across.”
Scientists believe that the first coyote to reach the island in 2017 swam the mile across the strait. Before then, Dexter-Lee said there’s no record of coyotes having ever lived there.
“There’s so far nothing in the archeological record,” she said. “[But] we intentionally don’t dig to try and preserve the history of the site.”
The first coyote lived on the island alone for a year and would exchange calls with coyotes across the strait in Tiburon.
“It’s possible that the second coyote came over intentionally because there was one coyote here,” Dexter-Lee said.
About a year after the second coyote’s arrival, Dexter-Lee said the first litter was sighted. She remembers seeing two coyote pups who had grown enough to leave the den. Today, the island is home to 14 coyote residents.
Since the coyotes arrived, scientists have noticed a shift in deer and raccoon behavior.
“Anecdotally, the island used to have a reputation for having a large raccoon problem, getting into the trash cans and interacting with campers,” Miller said. “But it seems like since we’ve had coyotes on the island, those sightings of raccoons have definitely gone down.”
The California Department of Fish and Wildlife estimates the current deer population on the island is around 50. But in the 1980s, the island hosted up to 300 deer — the state’s highest documented density of deer, according to Bay Nature.
Miller said that, at that time, the scientists had become concerned that the deer were too skinny and were impacting the island’s vegetation. Solutions like supplemental feeding, relocating the deer, contraceptives and even introducing coyotes onto the island were proposed. In the end, state parks decided to periodically cull the deer, which helped stabilize the population.
Several years later, the coyotes showed up.
Miller and other scientists from the California Department of Fish and Wildlife and UC Davis are now working on a five-year study about the impact of coyotes on the island’s ecosystem.
Dexter-Lee said coyotes tend to follow the same trails as people. Although coyotes generally are not dangerous to humans, she advises visitors who encounter the animals to raise their hands above their head to appear larger and then “tell the coyote” how they feel.
“You can say to the coyote, ‘Hey coyote, you’re too close, get away,’” Dexter-Lee said. “And not only does that let the coyote know that you’re a person, not something that they’re interested in, but also lets the people around you know that maybe you’re uncomfortable with the situation and they can help come over and shoo away the coyote.”
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