Indoors all the way. I've had some prior zoophilic experiences while outdoors before, but in my opinion nothing beats the safety and comfort of making love to your animal partner indoors. I don't want to run the risk of being caught, my animal partners mean the absolute world to me, and being caught means their lives are at risk, not just my freedom.
Not only that, but indoors means climate control. Why make love in the 95 degree F sunshine or 20 degree F cold when you can happily make love with your animal partner, in my case a beautiful female dog, in a nice 70 degree cooled/heated environment? Not only am I comfortable, she's comfortable too. And, I don't know about anyone else, but in the summer mosquitoes absolutely LOVE me. Hell, my blood is so enticing that they'll often bite me while wearing mosquito spray.