The Basenji dog is the only dog that is not able to bark.
4
If a vampire bat goes 2 days without drinking blood, they can die. However, well fed female bats will puke up blood and share it with other bats that they like in exchange for grooming.
13
A koi fish, named "Hanako", was owned by several individuals over many years and lived to be 226 years old, dying in 1977.
6
Sheep, goats, octopuses, and toads have rectangular pupils.
7
Parrotfish make themselves a kind of mucus 'sleeping bag' which masks their smell from predators and keeps parasites away.
4
Dolphins sometimes have fun by blowing bubbles and creating rings of air underwater, which they then swim through.
17