What are tails for? Animals have tails for several different reasons. They use them for balance, to grip things, for motion, as weapons, to lose heat, to communicate, and to keep flies off.
The majority of mammals, birds, and reptiles have tails, but not all do. Some insects have tails as well. Out of the mammals, koalas, humans, gorillas, chimpanzees, orangutans, bonobos, and some other apes don’t have tails. Out of the mammals, kiwis, and some other flightless birds don’t have tails. Out of the reptiles, frogs, and some lizards don’t have tails. There are even some fish without tails, but that tends to be rare because it is their means of transport. So, if the majority of mammals, birds, and reptiles have tails, what purpose do they serve?
Different animals have tails for different reasons. A lot of animals, cats, for example, use their tails for balance. When a cat is walking along a thin fence, its tail will be stretched up and will move around to control the cat’s center of balance. If the cat is leaning to the left, the tail will move to the right and if the cat moves to the right, the tail will move to the left. This is the same principle you would use if you walked on the same fence because you would hold your arms out. We balance by keeping our weight centered over our point of contact with the floor, which is our feet. If you lean forward, you have to shift your butt backwards so the center of mass stays in the same place. Your arms weigh about 5% of your body mass each. If you start to wobble to the left, putting out your right arm will keep more of your center of weight over your feet. That is why tightrope walkers use very long poles. An animal that uses its tail for balance follows the same idea.
Many primates and a lot of reptiles have prehensile tails that they can use to grip things. A prehensile tail can be used to hold things or pick things up, but the majority of animals that have them mostly use them to hang off branches. The tail is constructed with vertebrae, in the same way as a normal tail, but it has more muscle that can be controlled more finely. The tails can curl and grip objects with enough strength to hold the entire animal, and sometimes more. Many animals with a prehensile tail have a rough pad on it that they can use for gripping, and they can even feel with the tail.
A lot of animals that have a tail use it for motion. Fish wouldn’t be able to move through the water if they didn’t have a tail. Crocodiles, snakes, and other reptiles can move through water by whipping their tails back and forth to propel themselves forwards. Birds don’t really use their tails to move forwards, but the tails are vital for motion because they are one of the ways that the bird steers as it flies. That is why the birds that don’t have tails, don’t fly.
Many dinosaurs used to use their tails as weapons, but these days the number of animals that fight with their tails has declined. Porcupines, pangolins, aardvarks, and some lizards use their tails to fight off predators. Insects also use their tails as a weapon. Insects that sting do so with their tail, although it is not a tail in the same sense as an animal tail because they don’t have a backbone.
Animals can also use their tails to control their body heat. Animals that live in cold climates, such as wolves, can wrap themselves in their tails, keeping heat in. You may have seen your cat curled up like that. Some animals, such as rats, go the other way. They have tails with no fur and one of the reasons they have them is to lose heat. The tail increases their surface area and makes heat loss easier.
Animals use their tails to communicate as well. Cats and dogs use their tails to show excitement, anger or fear. Beaver slap the water with their tails to warn of predators. Skunks lift their tail to warn that they are about to spray, which is usually enough to make any predators run away. Deer flash their white tails to warn other deer of predators. And, of course, rattlesnakes are famous for using their tails to communicate their presence.
And, finally, a lot of animals use their tails to keep flies away from their rear ends. A lot of herbivores spend most of their time grazing and they defecate where they are. A lot of flies land on them, and the animals don’t mind, but they need to keep their rear ends clear of flies because the flies could lay eggs and that would be dangerous. Their tails are usually thin, which a brush of hair on the end and the animals use them like whips to clear the flies that settle. And this is what I learned today.
Photo by Rod Dion: https://www.pexels.com/photo/selective-focus-photography-of-brown-squirrel-939478/
Sources
https://www.sciencedirect.com/science/article/abs/pii/S0166432897001010
https://www.atlasobscura.com/articles/animals-weapons-tails
https://www.sciencedirect.com/topics/veterinary-science-and-veterinary-medicine/prehensile-tail
https://earthlife.net/do-insects-have-tails