Why Do Animals Have Tails?

Written by Patrick Sather
Published: September 16, 2021
Written by Patrick Sather
Published: September 16, 2021


Did you know that every person once possessed a tail? We grow tails in utero around the time we’re 31 to 35 days old, but then our tails regress and fuse into our vertebrae. The spot where our tail fuses is called the coccyx, or “tail bone.” Sadly, we don’t get to keep our tails, which is unfortunate when you stop and consider all the incredible functions that tails serve in the animal kingdom. 

Tails come in all shapes and sizes, from tiny tails that serve little to no function to massive tails half as long as an animal’s body. Animals use their tails for different reasons depending on specific evolutionary adaptations. The role of a tail differs between animals, and while some tails evolved for multiple purposes, others evolved for a particular reason. In this article, we’ll discuss some of the main functions of tails and provide specific examples of how animals use their tails in the wild.

Why Animals Have Tails

Kai Ken in a River
A Kai Ken with its tail pointed upwards.

With so many types of tails out there, it’s impossible to say precisely how many functions tails serve. While some tails clearly evolved to perform a specific task or to fulfill a biological need, the motivation behind the presence of other tails remains uncertain. In a broad sense, tails serve six primary functions. Although different functions exist, these six reasons occur most often and broadly. The functions of tails include balance, defense, navigation, communication, warmth or nourishment, as a part of mating rituals, and to mark territory.

For Balance

Are Marsupials Mammals
A kangaroo uses its tail for balance and to help propel it forward.

One of the most common reasons land animals evolved tails is that tails help animals balance. In these animals, a tail acts as a sort of counterbalance, allowing them to maintain their balance in precarious positions or move quickly and efficiently over rugged terrain. For example, cats developed tails to help them balance when walking over thin or uneven ground. In addition, their tails help them balance when running or leaping onto prey. Similarly, a kangaroo uses its tail to balance when hopping at high speed. Finally, squirrels use their bushy tails for balance when leaping from tree to tree. In these circumstances, the animal’s tail aids them in their movement. Although not essential for navigation, a tail that evolved for balance could mean the difference between a predator catching its prey or prey escaping from a predator.

As a Form of Defense

A rattlesnake shakes its tail as a warning to predators.

Another primary reason why animals developed tails has to do with tails’ role as a form of defense. Animals that use their tails for protection evolved ways to manipulate their tails to confuse, distract, or deter predators. For example, rattlesnakes’ tails developed to help them warn predators not to get too close. Their tails create a rattling sound when the keratin chucks rub together, hence the name “rattlesnake.” Meanwhile, some lizard species, such as green iguanas and bearded dragons, can detach their tails to distract predators. The lizards will cast their tails aside and hope that the predator pursues their tail as an easy snack so the lizard can make a quick and easy getaway. 

Other animals adhere to the adage that “the best form of defense is a good offense.” These animals use their tails as weapons to deter predators and to fight off would-be attackers. Case in point, the tail of a stingray, contains one to three venomous barbs. Stingrays rarely use their tails to attack prey but will whip out their tails to deter predators who get too close. Another animal whose tail possesses offensive capabilities is the porcupine. Porcupines rely on the hundreds of sharp quills covering their bodies and tails to ward off nosy predators. 

To Help Them Navigate

The World's Oldest Greenland Shark
A Greenland shark uses its tail to navigate through the frigid Arctic waters.

For many animals, a tail serves as a primary means of navigation or as an aid that facilitates more straightforward navigation. Animals that rely on tails to navigate do so because they adapted to particular environments where moving without a tail would be difficult. One of the most obvious examples of animals that use tails to navigate is fish. Most fish use their tails to propel their bodies through the water. They generate force by undulating their tails from side to side and leverage torques and twists to change their direction.

Monkeys count as another group of animals that use their tails to help them navigate. Some monkeys use their tails to grasp tree branches, which allows them to swiftly navigate through a forest canopy and avoid predators on the ground. Tails that evolved to grasp and hold onto objects are called prehensile tails and are one of the reasons why monkeys enjoy a reputation as nimble and agile animals. 

As a Means of Communication

two golden retrievers running together
A dog wagging its tail may mean it’s excited or happy.

Some animals also use their tails as a means of social communication. These animals use their tails to communicate simple signals to friends or foes, such as warning allies of nearby dangers or conveying emotions. For example, some deer species flash the white underside of their tails as a warning side indicating potential danger. Similarly, beavers will slap their tails against the water as a form of rudimentary alarm when they detect the presence of predators. In addition, every dog owner knows that a dog’s tail can indicate a lot about its emotional state. A wagging tail generally means a dog is excited or happy, while a lax, droopy tail may mean a dog is upset or distressed. 

For Warmth or Nourishment

Chinese alligator with its entire body on a rock
An alligator can store fat in its tail for nourishment during the winter.

Occasionally, animals will also use their tails as a way to ward off the elements. These animals adapted traits that allow them to use their tails to stay warm in cold weather. One example is the fox, which wraps its fluffy tail around its body as a kind of blanket. Other examples include coyotes, which will curl up next to their tails for warmth during cold nights. Meanwhile, some use their tails as a source of nourishment. Alligators will store fat in their tail that they use during the lean months in winter. Therefore, an alligator with a thick tail is a sign of a healthy, well-fed alligator. 

As Part of a Mating Ritual or to Mark Territory

Raggiana bird of paradise courtship - (Paradisaea raggiana)
Birds of paradise use their feathers as part of their mating ritual.

On rare occasions, animals will incorporate their tails into their mating rituals. These animals likely adapted to grow tails to help distinguish them from potential competitors for breeding opportunities. One of the best examples concerns certain species of birds, such as birds of paradise. Males grow beautiful and elaborate tail feathers that they delicately fan back and forth as a way to attract females. On the other hand, some animals use their tails to let other males know that their presence isn’t wanted. A male hippopotamus manipulates its tail like a propeller to fling its poop over a wide area to let other males know they aren’t welcome. 

Frequently Asked Questions About Why Do Animals Have Tails

Which animals have the longest tails?

Among land animals, giraffes possess the longest tail, which measures around 8 feet in length. Meanwhile, blue whales have the largest tail of any animal, which can reach up to 25 feet long.

Why do some animals swish their tails?

Animals may swish their tails for many reasons. Sometimes animals swish their tails to keep flies away. Other times, they may swish their tails to communicate emotions, spread pheromones, or warn would-be predators.