I’m trying to find the source, but I remember a primatologist claiming that humans and chimpanzees are the only two species that embark on genocide. Not being satisfied with simply defeating the enemy, but actively hunting them down to ensure they can’t harm you again. In other words, precluding retreat. (Which creates its own game-theoretical backlash: never retreat.)
Evidence is limited but orcas might also do that to great white sharks. The orcas seem to sometimes work together to exterminate sharks from an area in a way that goes beyond just hunting them for food.
Lions and Hyanas are well known for trying to exterminate each other's cubs (they rarely eat the carcases). Adults mostly avoid fighting each other as its too risky.
I think the difference is extermination from an area versus exterminating a line. Humans and chimpanzees will exceed their territory to eradicate foes. That, per this primatologist, is a unique adaptation.
Killing off another species isn't that much like genocide, which involves killing off a rival genetic line of the same species, but orcas do that too: https://pubmed.ncbi.nlm.nih.gov/29559642/
I don't think this falls under definition of genocide
> we suggest that infanticide is a sexually selected behaviour in killer whales that could provide subsequent mating opportunities for the infanticidal male and thereby provide inclusive fitness benefits for his mother.
I can see gene fitness benefit but mating opportunities, how?
"hey, me and maman uh killed your baby, wanna pump out a replacement real quick?"
It's really common.
In species where a prominent male has a harem of multiple females. This usually involves killing not only rival males, but all of their offspring too. Here's a Wikipedia article about it: https://en.wikipedia.org/wiki/Infanticide_(zoology)
In species which keep territories, animals will kill rivals of the same species, but because it's not targeted it's not genocidal, unless the species eusocial, in which case it can result in massive genocidal wars, e.g. https://en.wikipedia.org/w/index.php?title=War_in_ants
> usually involves killing not only rival males, but all of their offspring too
I think the distinction is between killing a line and killing a tribe. But granted, that’s valid.