A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Rattlesnake mating sessions have been known to last more than 22 hours.
232
The first known contraceptive was crocodile dung, used by Egyptians in 2000 B.C.
79
Parrotfish make themselves a kind of mucus 'sleeping bag' which masks their smell from predators and keeps parasites away.
4
A zoo in China gave a gay penguin couple the opportunity to raise a chick.
11
Blue whale arteries are large enough for humans to swim through and their hearts are the size of cars.
12