I think some actions are safe, but I also know (from a zoology perspective and a therianthropy perspective) that intercourse is painful and anxiety-inducing to a lot of animals. Even if pleasure is involved, they’ll still be expecting agony, and I know firsthand that just because something physically feels good doesn’t mean it does mentally. Besides, intercourse and merely the action of humping and/or things that mimic sex is a symbol of dominance among many mammals and that makes it emotionally uncomfortable. Plus, depending on the species, it can be dangerous for the human-bodied individual. Not just from a physical harm standpoint, but from a social and legal standpoint as well.

I’m both an (auto)zoophile and nonhuman, so this sure as hell doesn’t come from an anthropocentric standpoint. I simply think the physical and emotional risks outweigh the benefits. Plus I think you can still have a relationship with an animal without the risk of harming both of you. There are plenty of other things, like courtship, that communicate your love even better than intercourse!