Why do gorillas have such large nostrils?

Q: Why do gorillas have such large nostrils?
A: Because they have such large fingers.

This is a very uncommon joke. I have only ever hear it from one source, and I don't know where she heard it from. This joke is in the category of toilet humor, as the joke centers around the idea of picking noses.

The reason why it is funny is because the joke causes the hearer to consider why having a large finger would cause someone to have a large nostril. The conclusion that the hearer is supposed to come to is that the large fingered person would need a large nostril if the finger were supposed to be inserted into the nostril. It insinuates (but doesn't actually say) that gorillas pick their noses.