Earlier this year, a lone male coyote paddled through chilly, choppy waters and arrived at remote Alcatraz Island in the San Francisco Bay, stunning biologists and surprising visitors. National Park Service officials said the island’s status and setting—surrounded by swift water and known for thwarting escape attempts when it was a prison—made the sighting stand out. In the weeks after the animal appeared, researchers gathered evidence on the island, including fresh tracks and scat, and worked to determine where the swimmer had come from.
At first, the prevailing assumption was that the coyote had come from San Francisco, which is a little over 1 mile (1.6 kilometers) from Alcatraz. National Park Service wildlife ecologist Bill Merkle said that earlier working assumption was rooted in distance, adding that biologists could not help being impressed by the accomplishment of getting to Alcatraz from the city’s side of the water. “Our working assumption was that the coyote made the swim from San Francisco because it is a significantly shorter distance. We couldn’t help being impressed by his accomplishment in making it to Alcatraz,” Merkle said in a news release Monday titled “Alcatraz Coyote Wasn’t a City Boy After All.”
Biologists later learned the coyote had traveled even farther than originally thought. Merkle said DNA analysis showed the swimmer was part of the coyote population on Angel Island, approximately 2 miles (3.2 kilometers) away across the bay. “Coyotes are known to be resilient and adaptable, and he certainly demonstrated those qualities,” he said, describing the animal’s ability to make the crossing. With that finding, the earlier estimate based on distance shifted to a longer, more demanding route.
Camilla Fox, founder and executive director of the nonprofit Project Coyote, said coyotes can swim but that humans rarely witness it. Fox said the coyote likely left its home base to search for a mate or to establish territory. “We have never, ever heard such a story of a coyote making such a long journey in a pretty challenging ocean current,” she said. She added that the behavior fit the pattern of coyotes dispersing beyond familiar ranges.
The evidence in the park story built from multiple sightings and observations. Video from early January showed the coyote paddling in the San Francisco Bay and then struggling to get onto the rocky island. The animal was then seen again on Jan. 24, and photographs were taken by Rebecca Husson, who was visiting Alcatraz for a cousin’s wedding. Husson said her family was surprised to spot the coyote during a morning tour. “He looked like a drowned rat when he ended up on the island, and when we saw him he looked healthy and so beautiful. He looked like he had been eating well,” Husson told The Associated Press on Tuesday.
After the animal arrived, park officials said they were prepared to capture and relocate it because Alcatraz serves as a seabird nesting habitat. The park service’s assessment relied on DNA analysis of material collected from the island—fresh tracks and scat that officials sent to the University of California, Davis. Officials said they were stunned to learn the swimmer matched the Angel Island coyote population, and they said the coyote has not been seen again or caught on recording devices. They also said there is no evidence that the animal is still on the island.
Alcatraz Island became a federal prison in the 1930s, designed to hold people labeled as the worst criminals, before closing in the 1960s because operating it was too costly given its remote location. In the years after the prison era, the island reopened as a park, and the current management focus includes protecting habitats such as seabird nesting areas. Fox said coyotes have persevered on Angel Island despite the difficulty of colonizing the state park there, and she asked that visitors to Alcatraz and other nearby open spaces not disturb coyote families and their dens because it is pup season.