A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Condoms were originally made of animal intestines or linen.
347
The octopus does not have a blind spot.
273
The sound of a tiger's roar can travel a distance of up to 2 miles (~3 km).
255
When a male gentoo penguin "falls in love" with a female penguin, he searches the entire beach to find the perfect pebble to present to her.
25
A cat rubs against people not only to be affectionate but also to mark out its territory with scent glands around its face. The tail area and paws also carry the cat's scent.
293