These two polar bears walk into a Japanese zoo...

Zoo solves mystery of celibate polar bears

Puzzled zookeepers in northern Japan have discovered the reason why their attempts to mate two polar bears kept failing: Both are female.

Top ten responses from the zoo officials:

1) Not that there's anything wrong with that.

2) Well, the water is really cold.

3) Do we have any bi-polar bears?

4) It worked at the San Francisco Zoo.

5) Our DVM is an Aggie.

6) Maybe if we give her a crewcut ...

7) Think it would work better with two males?

8) Icicles

9) Don't Ask, Don't Tell

10) They're polar bears, would YOU want to check?