While they are hibernating, bears do not urinate. Their bodies convert waste into protein.

The wood frog can hold its pee for up to eight months.

A koala's poop is square.

Wombat feces are cube-shaped. Wombats stack their cube-shaped poops as a form of communication.

Sloths only poop once a week. They climb down from their trees, dig a hole, do their business, and then cover it up.

The hagfish is the only animal that has a skull but no spine.

Elephants are the only animals with four knees.

Kiwi birds are the only bird with nostrils at the end of its beak.

Sea Urchin is an animal that doesn’t have a single bone in their bodies.

Ants don't have lungs. Also, they never sleep.

A blue whale's tongue is heavier than an elephant.

A giraffe's heart, powerful enough to pump blood up its long neck, weighs about 25 pounds.

A cat has 32 muscles in each ear.

Octopuses actually have six arms and two legs!

An octopus has three hearts. Two pump blood to the gills, while the third pumps it to the rest of the body.

The severed head of a sea slug can grow a whole new body.

There's a jellyfish species called Turritopsis dohrnii, also known as the immortal jellyfish. This incredible creature has the ability to revert to a younger stage after reaching maturity, effectively restarting its life cycle. This process can occur multiple times, potentially leading to biological immortality.

Axolotl or Mexican walking fish can regenerate lost limbs up to 5 times and even regenerate parts of its brain.

A shrimp's heart is in its head.

The volcanic snail is the only animal in the world that has iron in its skeleton. Also known as the sea pangolin, it uses iron to build its shell and generate metal scales that cover its flesh, essentially becoming a snail with metal armor.

A small child could swim through the veins of a blue whale.

According to Diana Reiss, PhD, on the Star Talk YouTube channel, bees communicate both the location and distance of food by wiggling their bodies. They specify location relative to the position of the sun and they are intelligent enough to correct for the apparent movement of the sun in the earth's sky according to the time of day when the communication is taking place.

Bees can also sting other bees. Guard bees will protect the entrance of the hive. If an unknown bee trespasser attempts to get into the hive, these guards will sting the intruder.

Cats, dogs, and many nocturnal creatures appear to have glowing eyes because the back of their eyeballs include a special reflective layer called the tapetum lucidum. This helps animals see better in low light by working like a mirror on the retina to reflect the light back through the eyes.

A crocodile cannot stick its tongue out, but a shark can blink with both eyes.

Snails can sleep for up to 3 years. Although more usually they sleep for 15 hours followed by 30 hours of activity.

Just like human babies suck their thumbs, baby elephants sometimes suck on their trunks. They can also stand within 20 minutes of birth (though they can't see for a while, and instead sense their mothers through sound and smell).

Elephants are also the only mammal that cannot jump.

Rabbits can see behind them without moving their heads.

Rabbits also sleep with their eyes open.

Rabbits can't vomit.

White faced capuchin monkeys greet each other by sticking their fingers up each others' noses.

Blue Whale calves grow 200 pounds per day for the first year they are alive.

Giraffes don't need to spend energy to keep their necks up, but they do need to when putting their necks down.

Cats can't taste anything that's sweet.

It is physically impossible for pigs to look directly to the sky.

Honeybees can recognize human faces.

Bats are the only flying mammal.

These Alaskan frogs freeze almost completely at the start of winter, with two-thirds of their body water turning into ice. To all intents and purposes, they seem dead; their heart stops beating, and their blood flow stops. However, once winter starts to thaw so do they, and they hop back to life.

They secrete milk from specialized mammary glands, just like humans and other mammals. But platypuses don’t have teats, so the milk just oozes from the surface of their skin. This makes it look like sweat, but in fact, platypuses are aquatic and don’t produce regular sweat at all. Since this delivery system is less hygienic than the direct nipple-in-mouth method, platypus milk contains powerful antibacterial proteins to protect the babies from illness. These proteins may be a useful source of future antibiotics.

A cockroach can live over a week without its head.

Basenji dogs are the only breed that doesn’t bark.

Donkeys may not sleep in bathtubs in Brooklyn, New York. In Arkansas, it’s alligators that aren’t allowed in the tub, while in South Carolina, it’s horses.

Killer whales are the only animal that, when seen, divers MUST get out of the water, according to the US Navy dive manual, revision 6a.

Above a certain temperature, alligators only give birth to males.

Stick insects have sex with each other for up to ten weeks at a time.