Title says it all. 
(Well, okay, not quite all. I’m curious because, if the only mammals that suck on the female’s nipples during foreplay are also species that pair-bond with their mates, as humans do, it lends credence to the notion that the human mate-pair-bonding instinct may have evolved partially out of the mother-child-pair-bonding instinct.)
I think humans are pretty much the only species that screws just for fun. I’ve read some research that claims porpoises do, too, but there’s some disagreement about that. So I’m gonna say that humans are the only species that looks for erogenous zones away from genitalia.
If any species does it, it’ll be the bonobos (also known as pygmy chimpanzees). I think they’ve been observed doing just about any sexual behavior that a primatologist can bring themself to write down… they embody the “rule 34” of the natural world. Sex between any combination of bonobos (of any gender or age) is a major part of their social behavior.
But I am so not going to google “do bonobos play with nipples” while at work – someone else is going to have to step on that land mine. Suffice to say, nipples are not mentioned anywhere in the wiki page on bonobos.
bonobos do screw, suck and rub for bonding to group members and maybe fun.
don’t know about nipple sucking specifically.
i see that was mentioned will i had read and typed the above
I’ve read that boars stimulate sows’ nipples during sex, although I think they do it with their feet instead of their mouths.
No, but they don’t seem to mind when I do it.
As Cecil points out (at the end of the column), animals always do it for fun: http://www.straightdope.com/columns/read/55/do-female-pigs-have-six-minute-orgasms