This is one of the oddest and most brutal behaviors observed among animals. Sea otters, which appear so innocent and cuddly, are anything but when put next to baby seals.
There have been numerous documented instances of otters approaching baby seals on the shore, biting them on the nose, dragging them to sea, and then forcing intercourse on their helpless victims. Even after the seals have died of drowning, the attack continues for up to several hours. There have even been reports of otters copulating with seals that they had drowned up the seven days earlier! So why would they do this?
It is believed that when they cannot find a female to mate with, the otters become frustrated and simply adopt a baby seal instead. The actions they take on the seals are extremely similar to what they do to female otters, which also have the possibility of drowning while mating!