Is this funny?

In this month's Reader's Digest there is an interview with Emma Thompson. She relates one of her father's favorite jokes. It's not really a joke but it makes me laugh.

An elephant walking along the jungle path meets a mouse coming in the opposite direction. They stop and look at each other with interest. The elephant finally breaks the silence and says, "Why are you so small?" And the mouse looks up and says, "I've not been well."