I feel like horses and dogs are generally the most accessible to many people. A lot of us grow up around these animals, and sometimes our sexual and romantic maturity can coincide with theirs.

I believe that since both have been domesticated for thousands of years, and have learned to read human cues and body language, as well as humans being able to doing the same, the emotional bond can be easier to translate between species. Relying on each other for survival, can easily evolve into friendship, mutual respect, and in the case of zoophilia, romance and physical attraction.

Availability plays a major role in this. Compatibility is also a big factor, animals too small or too big practically exclude themselves. Cleanliness contributes its part , too...that´s why pigs, sheep, goats and bovines, although pretty common in rural areas, only attract people already into scat stuff or "dirtiness". The ability to control animals , the level of domestication is also a factor. And last, but not least, the sexual "performance" and special sexual "features" of the species play a major role , too. Stags and bulls only hump once, thus not very desirable for bestialists, for example. Sexual performance has to be compatible to humans to some extend for it to become interesting and /or desirable.

Well, there are many ways to look at it, but there are some rather important facts to keep in mind.

First, not all that many species have been domesticated, and I think that is a big part of it. I think it's likely that there is a bit of co-evolution that happens when a species is domesticated over a long enough period of time. Humans who were terrified of dogs didn't have as good of a success rate at survival in the past as those humans who could and would work well with dogs, as an example.

Another factor is "amount of connection". For sheep, and cows, and other livestock animals, they really don't interact on a very personal level with humans, so the effect I mentioned earlier would be diminished. You don't need to be able to form bonds with sheep on an individual level in order to herd them, or whatever else.

So with those two factors in mind, what we're looking for are species with a significant history interacting with humans, and where those interactions are generally on an individual rather than herd basis.

Dogs fit the bill, as do horses.

Cats have been domesticated for a while, but for most of our interaction together, they haven't been "housecats", I don't think. We don't work closely together - cats do their own thing hunting pests around food storage, without humans playing a role.

The only other species I can think of that would fit the same criteria as dogs and horses would be other beasts of burden - donkeys and camels, of particular note. However, those are also less common overall - camels are limited to a certain area, and donkeys are less common in the developed world than horses are, if I'm not mistaken.

I wonder if in North Africa and the middle east, where there is more of a history with camels, if the attraction to those species is likewise higher? I know it's a common joke to make about people from the middle east, but it's a serious question. Keep in mind that our perception of the "most common attractions" is going to be heavily skewed by the fact that most people participating in the communities we are familiar with are from certain areas of the world, with other areas being much less represented.

Mammals that are not dogs or horses (such as bovines, goats, sheep, pigs, llamas, alpacas, dolphins, etc.) are probably less common because the animals themselves are less common/accessible; and there would likely be more sexual relations if they were more common/accessible.

Pigs are actually clean animals, and the belief that pigs are "dirty" is a myth.

http://www.mirror.co.uk/news/ampp3d/egyptians-prefer-camels-bestiality-nation-5103938

What other people said, commonality and accessibility to said animals. Personally, I find other animals just as attractive. It would just be more realistic to take care of a dog than it would be a wolf...or a bear, or any number of animals that I'm attracted to.

I'd say it is because horses and dogs are both widespread and very social towards humans, at least once they are domesticated.

It is hard for a person to seriously like something they don't have experience with. It happens, because the human mind is weird, but it is easier to like an animal once you get in contact with it and realize all the facets of its body and mindset.

It's easier for people to anthropomorphize those animals. It's easier for them to feel like they can see those animals' emotional states by looking at their faces, just like they can with other humans.

Honestly I'm a bit surprised at all the "because domestication" believers. Maybe it's different things for different people, and those people enjoy whatever-it-is because of exposure or domestication. Similar to /u/CantThinkOfAName2017, I grew up with cats and small dogs and I find them both completely uninteresting.

To me, physically it's body type and certain facial features, emotionally it's personality.

This question strikes me a lot like posing the question to the normals of "why do so many of you own a horse or dog?" Sure they are more common animals, sure they are more traditional than some others. That doesn't stop people who really like llamas or goats or pigs from moving somewhere they can keep the type of animal they feel platonic love for.