A cat's bladder can only store a golf ball's worth of urine. For humans, it's a coffee mug and for elephants, a kitchen trash can. An elephant's bladder is 400 times the size of a cat's, but it doesn't take an elephant 400 times longer to pee. So, how does this work? David L. Hu digs into what scientists call the "Other Golden Rule." [Directed by Anton Bogaty, narrated by Jack Cutmore-Scott].