One day during field observations last year at Marion Island, a remote nature preserve in the southern Indian Ocean, something bizarre caught Tristan Scott’s eye: on a rocky beach, a sleek young male Antarctic fur seal was trying to mate with a king penguin. …

The fur seals normally hunt penguins and eat them. …

The phenomenon is called misdirected mating, and it extends to other marine mammals. Wildlife experts say sea lions and sea otters have occasionally been seen forcing themselves on other types of seals and killing them.

Indeed, some researchers say misdirected mating is not abnormal. “These things happen in wildlife,” said Heather Harris, a veterinarian who has studied sea otters in Monterey Bay. “We think that it is within the spectrum of possible normal behavior.” …

Nor is such mating limited to marine mammals. Insects, spiders, worms, frogs, birds and fish do it, too, Dr. Hochkirch said. The behavior is a form of so-called reproductive interference, in which an animal’s mate-recognition radar is imperfect; the encounters do not necessarily end fatally.