A lone coyote that swam more than a mile across the San Francisco Bay to Alcatraz Island is being monitored by scientists and could be moved if its presence threatens birds on the infamous Californian island.
The canine, called Floyd, appears to be thriving on The Rock - renowned for its abandoned prison - and getting by on an avian diet.
Whether Floyd can stay on Alcatraz depends entirely on how it behaves, says Aidan Moore, a local tour guide who shared footage of the coyote's journey.
Complicating matters, he adds, is that there are no fresh water sources, which could make the animal's welfare dependent on human intervention.
Video footage of Floyd - believed to be a male - hopping onto Alcatraz's rocks was captured by a tourist and shared with Moore.
The gaunt coyote appeared to be shivering from the bay water which is about 10C (50F). But he has plumped up since, says Moore, who is originally from the Cotswolds, in England.
On Saturday, the Golden Gate National Recreation Area (GGNRA) observed and photographed the coyote. The GGNRA confirmed to the BBC that the animal is believed to be the same coyote seen swimming to and coming ashore on the island nearly two weeks earlier.
Floyd is the first documented coyote presence on Alcatraz since the island was transferred to the National Park Service in 1972, the GGNRA said.
Park biologists and staff are actively monitoring the coyote to better understand how it is surviving on the 22-acre (89,030m) island and to assess any potential impacts to the seabird breeding colony, the GGNRA said.
The coyote's presence, it added, does not affect public access to the island, which remains open to visitors.
Alcatraz island - nicknamed the Rock because it was regarded as an impregnable fortress - is home to the shuttered federal penitentiary that housed some of the most dangerous criminals in the US.
Coyotes, the wolf-like creatures that are native to North America, are not uncommon in the San Francisco Bay. According to Moore, nearby Angel Island has at least 16 coyotes that are thriving there because there's fresh water and bigger prey, such as deer, that they can hunt.
But not so on Alcatraz, part of Golden Gate National Recreation Area, and a registered sanctuary for seabirds, whose sensitive nesting time runs from February through September.
Floyd has to be able to catch enough birds to sustain his dietary needs, Moore says, and suspects that catching them is like shooting fish in a barrel given the thousands of birds there.
Kessler suspects Floyd made the journey because he might have felt interspecies population pressure in the city and needed to find a new territory.
Coyotes could be leaving the mainland because the Bay Area is becoming too crowded, a wildlife ecologist noted.
While coyotes are adaptable and natural survivalists, tour guide Moore is worried about Floyd's future and is pushing for human intervention. But finding him might be a challenge as coyotes are masters of disguise.
Floyd seems to be hiding in areas that are not accessible to the public.
