Scientists are documenting "sexual coercion" in the Antarctic, and it's probably not anything like what one might think: Young male Antarctic fur seals, it seems, have been documented having sex with King penguins of undetermined gender, reports the BBC, via a study in the journal Polar Biology. Scientists observed a male seal unsuccessfully attempting to mate with a penguin in 2006, but dismissed it as a one-off.

But researchers says they inadvertently observed the same thing on at least three separate occasions. "Honestly I did not expect that follow-up sightings of a similar nature to that 2006 one would ever be made again, and certainly not on multiple occasions," says a study co-author.

It's believed to be the first instances of pinnipeds—which include seals, fur seals, and sea lions—having sex across biological classes, as the BBC notes, "in this case a mammal trying to have sex with a bird." Some of the seals are believed to have penetrated the penguins, and one instance turned bloody, with the seal killing and eating his victim, though that's not unusual.

It's not clear what's driving the behavior, though scientists speculate that it's a learned behavior; that would explain the increase in sightings. "I genuinely think the behavior is increasing in frequency," says the co-author.

Other theories include the seals blowing off sexual frustration, or using the weaker birds to practice. "All in all it's difficult to say really," says the co-author.

(Meanwhile, a study previously revealed that penguins are pretty sexually depraved themselves.)

This article originally appeared on Newser: Seals Busted Having Sex With ... Penguins

More From Newser