i guess because there are so many accepted differences between humans and every other living thing in the world i would expect that somewhere down the line (though far far down the line judging by where we are now) it would also be accepted that all things that aren't human are referred to by their physical sex because they cannot communicate their gender identities to us. humans can and eventually i think people will finally respect that.

or perhaps we will be able to communicate with them to a point where we will be able to find those things out. (actually i would be really interested in how my male cat feels about it seeing as i call him "princess" and "drama queen" all the time)

IT'S REALLY TOUGH but the fact is it's just different. animals have fluid gender identities (as far as I'm concerned) but they don't feel the need to project them in a way we understand because it's not a big deal to them so we just use their sex as an indicator for what pronouns we should use.