How do they find the right hole? They can’t really see what they’re doing, and they don’t get anatomy lessons. Seems to me they would end up doing it anally about half the time.
Reptiles don’t have this problem, as they have only one opening.
Practice Practice Practice!
If she kicks you, you’re doing it wrong.
I’m getting flashbacks. Didn’t we have a confused and strangely inexperienced Doper here at one point who asked the same thing about humans?
Presumably, the answer is the same: One opening is a lot more naturally accommodating than the other, unless you bring a lot of lube.
The anus is behind the vagina.
The penis extends out beyond the location of the vagina tilted at an upward angle and tends to encounter the vagina first.
In addition, the vagina and anus are each tilted slightly away from each other, with the angle of the vagina being easier to access.
(I have no idea whether this actually prevents accidents from happening, but it tends to make the process more likely to occur correctly.)