Human circadian rhythms (sleep/wake cycles) are twenty-five hours long. Days on Earth are twenty-four hours long. That’s why it’s so hard to stick to a sleep schedule.
Sharks were the first animals to have penises.
Neoteny is a word that describes an animal that has evolved to keep the characteristics of its ancestor’s young for its entire life. For example, dogs have the floppy ears and barks of wolf pups. There is a theory that this happened to humans. Think about it: we are barely fuzzy like baby monkeys and we keep learning for our entire lives. If you ever feel old, this fact should comfort you.
Octopuses keep some of their brain in their arms. So their arms will swim around and look for food for a while after they are severed. Side note: According to scientific convention, the word is octopuses, not octopi.
Bulldogs should not exist. They can’t breath all that well and have a lot of other expensive health problems.
There has been a fifty-year experiment going on in Russia to breed domesticated silver foxes. They are adorable.
Some airlines keep falcons to scare away other birds that might get stuck in propellers.
The males of some dragonfly species grab onto their mate’s head with special clampers and hold her over a body of water until she lays her eggs.
There is a species of musk deer that grows fangs instead of tusks.
Water striders have post-coital communications with the vibrations of their feet.