Also, I’d like to know why one animal doing one thing is used to justify human behaviour as “natural” while another animal doing something else is not. (Or even the same animal doing something else is not.)
There are tons of non-territorial animals, for example.



Why are some things that some animals do used as a justification for humans to do the same, while other animals doing something else isn’t?
For example, Wikipedia says this about the topic:
https://en.wikipedia.org/wiki/Territory_(animal)
It is natural to not have borders, and only a few species do.