Bi.Polar.Bear, I was just glad you didn't CHOMP me.

One of Central Park Zoo's polar bears was diagnosed as depressed, some 10 years ago. Gus, the depressed bear. Honestly, I am not making this up: he would apparently swim back-and-forth in the same pattern all day long. They treated him by varying his day with interactive treats (a ball with a snack inside, etc.) and also made him an air-conditioned room where he could chill on his own. One theory held that his being around the other, female bears might have been irritating him, as males in the wild are supposedly not used to being around females much of the time.
I found it all sincerely fascinating.