BusyCowboy

The South African-based scientists who witnessed the incident say it is the most unusual case of mammal mating behaviour yet known.

The bizarre event took place on a beach on Marion Island, a sub-Antarctic island that is home to both fur seals and king penguins.

The scientists who photographed the event speculate that it was the behaviour of a frustrated, sexually inexperienced young male seal. Equally, it might be been an aggressive, predatory act; or even a playful one that turned sexual.

The 100kg seal first subdued the 15kg penguin by lying on it.

The penguin flapped its flippers and attempted to stand and escape - but to no avail.

The seal then alternated between resting on the penguin, and thrusting its pelvis, trying to insert itself, unsuccessfully.

After 45 minutes the seal gave up, swam into the water and then completely ignored the bird it had just assaulted, the scientists report.

Sexual coercion among animals is extremely common: males of many species often harass, coerce or force females of their own kind to mate, while animals are also known occasionally to harass sexually a member of a closely related species.

This is thought to be the first recorded example of a mammal trying to have sex with a member of another class of vertebrate, such as a bird, fish, reptile, or amphibian.

The penguin did not appear to have been injured by the seal, the scientists report.