Those cute sea otters that crack clams open to eat can be vicious. They’ve been observed raping and in the process killing juvenile seals in California. The sea otter comes up at the baby seal and bites it's nose repeatedly leaving large lacerations.
It then mounts the baby seal in the water and drowns it while it rapes it. The way the male sea otter goes at the seals is typical of how the sea otters mate. Female otters are known to die during the mating process, too. They die of either wounds from bite marks and scratches or drowning.
Stronger male otters establish territories with high numbers of females and work to exclude the other males from the territory. The excluded males, or rejects, meet up and make their own area and live together as bachelors. It’s those bachelors that attack the poor baby harbor seals and rape and kill them.