What are some things that are considered normal when done with other species, but are seen as disgusting when done with other humans?

Mounting heads/bodies, or hides on your floor, to show your hunting prowess.
Leading other humans around on leashes, unless that’s your kink.
Eating the babies and stealing the mother’s milk.
Caging kids, like baby cows for veal, with no exercise, for a menu item.

You are so funny, Loli.

Well dogs sniff each others ass,as I guess as a way of saying hey I know you.
Glad we humans don’t do that.

Killing them when they annoy us at all.
Killing them when they enter our homes.
Letting our children imprison, torment, dismember and kill them in creative ways for fun (bugs, at least).
Killing them for sport (hunting).
Dissecting them to learn and teach about anatomy.
Using them for science experiments.
Castrating them.
Branding them.
(so many more things…)

Running around buck naked.

A bird regurgitating to feed it’s young.

cannibalism.

Defecating in public has to be right up there.

This question is really, really unclear. By “done with other species”, do you mean “done by human to other species” or “done by other species to each other”? So far I’ve seen so many different answers just for this question.

@Zaku Dissecting them to learn and teach about anatomy.

During the old time, it was socially acceptable to dissect dead criminals to learn about anatomy. That is how we developed our current knowledge of the human’s body and the act of autopsy, which still proves to be important today.

@Mimishu1995 (NSFW) they also did dissections on live
criminals. Is called vivisections. I recommend not Googling.

(NSFW) Actually one lady from the 1001 ways to die television series got off from being vommitted on. She choked on a hot dog from a famous speed eater. After a competition.

Trust me you don’t want a link.
Don’t spend too much time visualizing.

A few times a day a neighbor walks her dog on my road. She picks up his poop and puts it in a plastic bag she ties to the leash.
We think she is thoughtful and nice.
If she did that with her husband, we wouldn’t.

I agree with @Mimishu1995 . I don’t understand what the question is asking although maybe @LuckyGuy has the right idea.

The thought that came to my mind was monkeys grooming each other by picking nits out of their friends and family’s fur and eating them. However, that is an inter-species habit not a human to animal habit (I hope.)

To clarify:
Humans doing something to or with other non-humans, as compared to what they do to or with other humans.

I pet my pet. I don’t pet my friend.

^^ I think I still got it wrong! Oy vey!

@janbb
Or did you?

I didn’t mean to tell but ooh – penguins!

A very lucky pet indeed!