without much in the form of being selective, too young to breed, too old to breed, same sex, different animal species it doesn't matter.

Consider harbour seals. Age has nothing to do with who wants what. Harbour seals and walruses are both like that.

Then, as an extra example, consider the porpoises. Especially the ones in Austrailia and New Zealand. From the science videos on Discovery, Nature, and, of course, YouTube, there are several accounts of these mammals making moves on humans in the shallow waters. Some are downright horny. And they are like that with their own species, as well; old and young alike.

And then, also, there are the bonobos...

As for sex being dirty, well, that depends on your idea of kink. I know some XXX videos show these two women wrestling in mud. Not my thing, but that would be considered dirty, wouldn't it?