What animal routinely attacks another on sight--not for food?

A mother duck when seagulls are around. Swans are nasty

A skunk will spray if upset.

Bottle nose dolphins will kill sharks in the area of a female dolphin about to give birth

All the above attacks listed are about defense of self or young.

Terriers go after rodents, having been bred for that by humans.

Some well-fed cats will attack things that move in a stimulating way. That’s a hunt/play response, though, not an enmity.

Terriers after rodents, I think that’s more like what I’m looking for: a spontaneous, unprovoked attack by critter A on critter B just for being what it is. Just the sight of B is enough to trigger A.

Thanks. Any more?

Like a Coyote on a fox. I saw it happen. The coyote took off like a heat seeking missile.

@LuckyGuy, is that territorial?

Bull moose will kill anything in their territory at certain times of year.
Hippos kill anything they don’t like

What about human-animals? Do they count? (Not being facetious.)
Do badgers,wolverines, or possums behave this way? Don’t brown recluse spiders attack “just because”?

Ive seen both hawks and eagles driven off by much smaller birds.

I read somewhere that dogs typically don’t attack cats just because. Dogs are more social than cats and will approach cats because that’s how they socialize. Cats on the other hand see this behavior as a threat to their safety and will run away. On the outside this looks like the dog is chasing the cat out of some unknown hate.

Back to the question, I think there’s the dolphin and the shark. They don’t see eye-to-eye just because one can potentially get killed by the other, not because of some predator-prey relationship. Also wasps aren’t kind to bees.

Almost any female of any species when she thinks her young are threatened. A mother moose is very dangerous! Or a hippo or elephant, to mention but a couple.
I’ve heard that a mountain lion or wolf will go on a rampage and kill many sheep. So will a fox or skunk in a hen house.

Bears go after humans a lot, but here’s bears and a cowboy scared of each other.

Nobody is safe when cats get the eff you mood. They even have a song about it.

These apparently kill most anything they see.

Dogs after squirrels. People on spiders or snakes.

People on spiders and snakes?
People kill anything and everything for sport. Birds, mammals, reptiles, fish; you name it we hunt, trap, wrestle, extinct it.

Jackal
Tasmanian Devil
Shark

Sometimes sharks cut humans a break.

For gosh sakes, read the comments, they are golden!

Bull moose in mating season is claiming territory for mating rights.

Hippos are dangerous but AFAIK it’s generally about mating and territory… it might be true to say they attack whatever they don’t like, but is there much they don’t like without some reason?

According to this article brown recluse spiders do not attack “just because”.

Small birds chasing away larger birds is quite common and almost always because they don’t want their eggs eaten, and/or for territory reasons. This might count as enmity, though with a good (or territorial) reason.

Some dogs are fine with cats. My first cat though was killed by loose dogs in our own yard. She was old and was not aggressive, so at least some dogs will go kill a cat. Whether it’s hate or a sense of what they think they’re supposed to do, I don’t know. It might vary per dog.

I didn’t know wasps generally went after bees. I haven’t seen that, and I have seen a lot of wasps near bees. I have heard and read that wasps go after some other insects, including many insects that go after plants, but they do it to feed them to their young.

Not all bears are very dangerous to humans. Grizzlies and polar bears yes. Brown bears no.

Hamsters. They’re solitary and will start to attack each other when they’re a certain age, even if they grow up together.

And yes, dogs, lots of them. The dog breeds with the highest prey drive include sighthounds, sled dogs, and terriers. Sighthounds especially will start to twist around and almost scream if they can’t get to their prey.

@Jeruba I do not know whether the response is territorial or not. I just witnessed the action. It was over in 2 seconds. The fox was ambling out of the apple orchard. and the coyote was standing in the mowed field about 50 yards away. It suddenly took off and blasted into the fox. Both tumbled from the impact before running their separate ways.

Other possible examples
A doberman or pit bull on anything
A fox in a chicken coop.

Lions, will kill Hyenas. They don’t even eat them…. It’s, for lack of a better word, pure hatred…

Female Cowbirds will find another breed’s nest, and when the “owner” is away, remove one or more of the existing eggs and lay their own. The new eggs are then hatched and nurtured by the nest owner, relieving the egg layer from the responsibility of raising their brood.

A cat will attack your leg as your sound the corner of the sofa, just for fun (practice?).

@Pied_Pfeffer Why didn’t I think of that?

House Sparrows chase Blue Jays and Crows in flight.

Mocking birds are fairly ruthless as well should any living creature remotely approach their nest, even with the most innocent intention. They dive bomb other birds, animals, humans, etc.

@LuckyGuy Pitties and Dobies are not born that way. They can be trained that way.

Hippos.

A friend told us that a mink broke into an enclosure at his uncle’s hunt club and killed most of the pheasant.
They weren’t eaten, just killed.

That seems odd.

This thread, got me thinking. There are serial killers, in the human race. Since humans, are essentially animals, maybe there are “serial killers,” in other species…
Just a thought….