Amazing animal facts that sound unreal

Science, Nature & Culture · 5 min read

Nature is stranger than any fiction. The following facts sound like exaggerations, yet each is well documented by biologists. Share them at the next dinner table and watch the raised eyebrows.

Octopuses have three hearts and blue blood

Two of an octopus's hearts pump blood through the gills, and the third circulates it to the rest of the body. Their blood is blue because it uses a copper-based protein called haemocyanin to carry oxygen, instead of the iron-based haemoglobin that makes human blood red. Curiously, the main heart stops beating when the octopus swims, which is one reason they prefer crawling and tire quickly when swimming.

A group of flamingos is called a flamboyance

Flamingos get their pink colour from pigments in the algae and small crustaceans they eat. Chicks are born grey. If a flamingo's diet lacks these pigments, its feathers fade. Large flocks can number in the thousands, and these groups really are called flamboyances.

Some jellyfish can reverse their life cycle

The jellyfish Turritopsis dohrnii, sometimes called the immortal jellyfish, can revert from its adult stage back to an earlier polyp stage when stressed or injured. In theory, it can repeat this cycle. In practice, most still die from predators or disease, so "immortal" is a little dramatic, but the ability is real and scientists study it.

Bees can recognise human faces and do simple maths

Experiments have shown that honeybees can learn to tell human faces apart using a pattern-recognition strategy similar to how we process faces. Other research suggests they can grasp concepts such as zero and simple addition and subtraction. They also communicate flower locations through the famous waggle dance, which tells their hive-mates the direction and distance of food.

Sloths descend only about once a week

Sloths spend most of their lives in trees, and typically climb down roughly once a week to defecate. Their slow metabolism means that digestion of leaves can take days or even weeks. Algae grow in their fur, giving them a greenish tint that helps with camouflage. Despite being slow on land, they are surprisingly capable swimmers.

The mantis shrimp can punch with extreme speed

Certain mantis shrimp strike with club-like limbs at such speed that the water around them briefly vaporises, creating tiny cavitation bubbles. The blow can crack shells and even aquarium glass. They also have remarkably complex eyes, with many more types of photoreceptors than humans, though how they use this information is still debated.

Crows remember faces and use tools

Studies of American crows found that they can recognise individual humans and remember who threatened them, even teaching others in the flock to be wary. In New Caledonia, crows craft hooks from twigs to fish insects out of holes. Corvids, the family including crows, ravens and magpies, are among the most intelligent birds.

Dolphins sleep with half a brain

Because dolphins must surface to breathe, they cannot fully switch off. They let one half of the brain sleep at a time while the other stays alert, in a process called unihemispheric slow-wave sleep. The eye connected to the awake hemisphere typically stays open. Some other aquatic mammals and certain birds show similar behaviour.

Hummingbirds are the only birds that can fly backwards

A hummingbird's wings rotate in a figure-eight pattern, giving it power on both the up and down stroke. This lets it hover and fly backwards, which is handy when feeding from flowers. Their hearts can beat well over a thousand times a minute during active flight, and they must feed often to fuel such a fast metabolism.

Wombats produce cube-shaped droppings

Research on wombat intestines found that variations in elasticity along the gut shape the faeces into cubes. Wombats seem to use the cubes to mark territory, since the shape makes them less likely to roll away from rocks and logs. It is one of the few examples of cube-shaped biological products.

Cows have best friends

Studies have found that cows form close social bonds, and spending time with a preferred companion can lower their heart rate and stress levels. They also have excellent smell and a wide field of vision. Many ancient cultures, including in India, have long respected them for their gentle nature.

Elephants may mourn their dead

Elephants are known to linger around the bodies of deceased herd members, touching them with their trunks and feet. Researchers have recorded behaviour that looks like grief, although scientists are careful about interpreting it as human-like emotion. What is clear is that elephants are deeply social animals with long memories and strong family ties.

Animal	Quick fact
Octopus	3 hearts, blue blood
Dolphin	Sleeps one brain half at a time
Hummingbird	Can fly backwards
Wombat	Cube-shaped droppings

Tip: If you are curious about fact-checking, search for the species' scientific name and read pages from museums, universities or national wildlife organisations.

Final thoughts

Every animal has adapted to its world in clever ways, and scientists are still discovering new behaviours. Many of these species are threatened by habitat loss, so enjoy the facts, but also support wildlife conservation where you can, for example by protecting local green spaces and avoiding products linked to habitat destruction.