I had not previously encountered the term “cougar” (clearly I’m not going to the right clubs), but here’s the highest-ranking urbandictionary.com definition:

An older woman who frequents clubs in order to score with a much younger man. The cougar can be anyone from an overly surgically altered wind tunnel victim, to an absolute sad and bloated old horn-meister, to a real hottie or milf. Cougars are gaining in popularity—particularly the true hotties—as young men find not only a sexual high, but many times a chick with her shit together.

A colleague of mine was ruminating on the fact that we need a name for the boys in this context; if the ladies are the hunters, what should we call the prey?

She has suggested “mantelope”.