I guess I have to say I've always been zoo - I was 8 or 9 when I had my first orgasm (though I didn't know at the time there was such a word, never mind what it meant) from putting my penis (at the time, I only thought of it as my "pee thing") inside Brandy, the family dog. At that point in my life, I had no idea what sex was - I only knew that sometimes, Brandy's pee would smell different than usual, and when it did, she'd let me put my fingers in the place where it came out, or lick and nibble there (If you'd asked me why I'd want to do something like that back then, I'd have stood there with a stupid look on my face and wouldn't have had a clue how to answer - I only knew I had the most intense urge to lick her there whenever her pee smelled that way, with no idea why I should want to) and my "pee thing" would get stiff and stand up straight. Dunno how I ended up putting 2+2 together, but that fall, her pee smelled different twice instead of only once, and the second time, her "pee place" tasted extra good when she let me lick it. Only now, instead of staying laid down when I tried to put my finger inside her, she stood up and turned her butt to me, and moved her tail to the side. That's when I realized that when she was standing up, her "pee place" was just about the right height so that if I was kneeling behind her, my "pee thing" would be able to touch her there - I think I might have wanted her to pee on my "pee thing" for some reason, but <shrug> Dunno. Anyway, I got my pants off, and got behind her, and as I started touching her "pee place" with my hard "pee thing", she stared to move her butt up and down, and when she did, my "pee thing" went inside her "pee place", and it felt so good I didn't know what to do - So I froze, pressing against her butt with my pee-thing inside her. It was so warm and wet (and I couldn't figure out why it was wet - had I found the real source of her pee?) and she kept moving her butt, and something happened inside me, way down deep inside, almost, but not quite, behind my "pee thing". I didn't know what it was, but it sure felt good. That's when Brandy stopped moving her butt, and because I wanted the good feeling to keep on, I started moving my "pee thing" in and out of her. That felt just as good as when she was moving her butt up and down, so I kept going, hoping that it would make the good feeling keep on happening. It did - and kept getting stronger and stronger, until it was like something popped inside my belly, way down there behind my "pee thing", and the good feeling got so strong I was seeing spots, then something down there behind my "pee thing" started sort of "squeezing", and the good feeling turned so intense it almost hurt, but even so, I didn't want it to stop. After a few seconds, the squeezing inside me stopped, and moving inside of Brandy started to actually hurt - the good feeling faded away, and almost at the same time, I just *KNEW* I *HAD* to pull my "pee thing" out of her before "something bad" happened. I had NO idea what the "something" could possibly be, but I just knew it was going to happen, whatever it was, and I wouldn't like it, so I jerked out of her. She yipped as I did, and I was worried I'd hurt her for a moment, but she just laid down and went to licking herself there, and I noticed that my pee thing was almost all the way soft. Of course, at that age, I didn't know about sperm, or any of the details, but remembering back to it, it's obvious that I'd had an orgasm, but since I wasn't yet producing semen, I hadn't left anything inside her. I wouldn't experience an actual "semen comes out" ejaculation until I was 14 going on 15 but by then, I'd already had something like a dozen orgasms from the times Brandy would let me mate with her. Not that I knew that's what I was doing at the time - I only knew that she didn't seem to mind letting me put my "pee thing" inside her, as long as it was when her pee smelled different and her "pee place" tasted especially good. Any other time, she'd either get up and walk away, or growl and nip at my hand if I tried to put a finger inside her, so I knew not to try to put my "pee thing" into her unless it was during the times when her "pee place" smelled and tasted good, and she didn't mind me putting my finger inside her first - At those times, she'd nearly always stand up and present herself so that I could easily put my "pee thing" inside her the way she'd done the first time.
Since then, I've been actively zoo - though not exclusively so - I've had my casual sexual encounters with humans, but just never really cared enough for it to bother making any effort in that direction. If the privacy for the act is available, I'll have sex with most any female critter who shows willing, and seems likely to be able to physically accept me penetrating her, and I enjoy being topped by or doing oral sex on male dogs. If a woman who doesn't punch one of my "yuck" buttons offers me a "no strings attached" or "friends with benefits" level fuck, I won't turn her down, so long as she realizes that's exactly what it is: The enjoyment of a fuck, with no emotional attachment on my part. It's not that I "hate" humans as sexual partners, I simply don't bother TRYING to have sex with a human. If the offer is made, fine - The chance to mate will almost always be taken when offered. If nobody ever makes the offer again, I'll go through the rest of my life not missing it, perfectly content with my four-legged partners - who I actually care about, unlike humans.