A lone coyote stunned biologists and others when earlier this year it paddled its way to the remote Alcatraz Island, a former federal prison in the San Francisco Bay surrounded by swift, choppy waters notorious for thwarting prisoners’ escapes.

At the time, biologists guessed the coyote swam from San Francisco, which is a little over 1 mile (1.6km) from the fortress. But it turns out the male coyote actually made an even longer swim from nearby Angel Island, 2 miles (3.2km) away.

“Our working assumption was that the coyote made the swim from San Francisco because it is a significantly shorter distance.…