When is a cougar just a cougar?

It's been a while since I last posted - no excuse other than been busy with life!
Here's a question - what's with all the cougar talk of late? How did women of a certain age become known as cougars? I looked up the definition of cougar - the animal variety is a mountain cat, a sleek fierce wild cat. The urban dictionary says a cougar is - a woman of a certain age looking for men younger than herself. I don't get it - where is the correlation? And why the cougar? Why not a lioness? Or a tigress? And if a woman of a certain age looking for a younger man is called a cougar, then what is a man of certain age looking for a younger woman called? The only animal analogy I could of, and its not nice, is a bear - it sleeps all winter, is covered in hair, wakes up cranky looking for food, generally smells, and often carries weight around the middle! Sorry - I said it wasn't nice!