Tails are the long, typically muscular rear parts of many animals that serve multiple functions; from helping cats balance during running to swatting away insects from cattle to helping guide birds in flight and conveying social cues between wolves.

Also referred to as butt (U.S. slang), backside, bottom, buns, derriere (Brit. slang) or “jacksy” (U.S. slang).


Animal tails vary in shape, color and size among them, yet all share six key functions that they serve: balance, defense, navigation, communication, warmth/nutrition or marking territory.

Most animals with tails – such as cats, dogs, whales, cheetahs and monkeys – use them for balance or propulsion; bird tails help direct flight while insect wings provide propulsion; cows and horses use their tails swish them around to keep flies at bay; some New World monkeys and opossums even possess prehensile tails which enable them to grasp tree branches with their long tongues; these functions all play an essential part in an animal’s survival; additionally it increases chances of survival during natural disasters while making mating easier between species. All these functions play their roles when used properly! All these functions play an essential part in survival; increasing its chances of surviving natural disasters while increasing chances of attracting mate opportunities among species alike.


Tails have been one of the key anatomical evolutionary adaptations accompanying vertebrate evolution from fish-dwellers to land dwellers, but until recently scientists did not understand how their molecular mechanisms work to form distinctive tails in certain animals.

Scientists have begun the journey toward understanding this process by identifying the genes responsible for creating tail formation. Researchers have already discovered 30 separate genes essential to tail development – from an iguana’s long whiplike tail to the short one found on Manx cats. Although most of these genes can be found elsewhere in an embryo’s development process, others such as TBXT appear specific to tail end development only and become active at certain points as the tail lengthens further.

Noggin gene activity plays a key role in how long the tail stretches, working alongside proteins like Shh and Bmp4 to promote somite induction, segmentation, and differentiation, leading to gradual addition of vertebrae in its length. As somites proliferate further along their tail path, their balance becomes disrupted between Noggin and Bmp4, leading to its expression rising at neural tube end as neural crest cells migrate down its length in what’s known as “axial termination.”

As the process of axial termination proceeds, Noggin and Bmp4 balance shifts further toward Bmp4, leading to further tail extension. As this continues, however, apoptosis kicks in, which causes somite cells to die off and ultimately stops its further extension.

Researchers conducted extensive genomic research on six tailless ape species and nine tailless monkey species that lack tails to locate a mutation only found among humans, and absent from other primates or monkeys, that might explain our lack of one. They discovered this mutation in TBXT gene; when genetically tweaking mice with it many did not grow tails at all while some only developed short ones; suggesting it is indeed responsible for our tail loss.


Human embryos during their 5th to 6th weeks in gestation typically feature a tail composed of 10-12 vertebrae; by week eight of gestation however, this tail no longer exists.

Born babies may sometimes feature bony protrusions at the base of their spine that have been described as vestigial tails; these bony protrusions have been reported as vestiges of our long-gone evolutionary ancestors’ tails; however, it is actually caused by birth defects which results in abnormal spinal cord development, often associated with spina bifida or meningocele; this condition is commonly referred to as pseudotails.

As with many birth defects, having a pseudotail can have serious health implications. Therefore, doctors suggest having these babies examined by an experienced neurosurgeon who will assess any tethering issues or any spinal problems and provide appropriate care while offering hope of positive results.

These cases have been reported by various countries worldwide and generated great excitement and speculation in the media. However, true human tails are extremely rare occurrences with only 40 cases documented worldwide so far. Soft protrusions at the base of the back that appear finger-like are called tails; males seem more likely than females to exhibit them and tend to develop them alongside underlying spinal dysraphism.

Although caudal appendages are relatively rare, they are relatively straightforward to treat and removal should cause minimal trauma to patients. Indeed, this operation may even be less invasive than performing a coccyxectomy (the removal of the coccyx). Surgical treatment entails both the removal and correction of the pseudotail. These patients should undergo an MRI study to confirm the presence of a tethered spinal chord and assess for additional areas of pathology such as spondylolysis or herniated discs that require surgical correction. But sometimes children with pseudotails refuse to have them removed due to cultural beliefs or fear of rejection. In such instances, it is vitally important that education and information regarding these anomalies is provided so they can be accurately diagnosed and treated.


As tadpoles develop into frogs, they usually shed their tails. But sometimes tadpoles may retain this feature and use it for stability in the water or to tap nutrients stored there – much like monkeys who hang from branches by using their tails as swings! This strategy may help tadpoles survive predators in environments with frequent predation.

One study by scientists involved surgically manipulating the depth of Hyla versicolor tadpole tail fins to study their effect on swimming performance and survival rates in captive Hyla versicolor tadpoles. While maximum speed and time to travel 2.5 cm did not differ between groups, those with deeper tail fins did have reduced survival odds after being attacked by fish or dragonfly larvae, leading researchers to theorize that such plasticity promotes adaptive fitness by changing with their environment.

Researchers conducted by another group discovered that relative depth of tadpole fin, rather than length, predicted its burst swimming speed. Their results support their theory that relatively deep tails of predator-induced tadpoles help avoid predation in two ways: either by diverting predator strikes away from vulnerable areas such as head and body regions or by improving performance during burst swim phase.

The team created predator stress by placing tadpoles in a tank with caged dragonfly larvae and measuring corticosterone levels (similar to human cortisol), which increased when under potential predation threat. They then used corticosterone-infused culture dishes to grow disembodied tadpole tails–sure enough, these tails became bigger with time!

However, these changes did not hinder the tadpoles’ abilities to hide from simulated dragonfly larvae or absorb water or forage effectively. Furthermore, canonical correlation analysis was employed by researchers to examine whether there was any direct relationship between morphology and swimming speed of each individual tadpole and swimming speed or whether their deeper tails allowed them to absorb more water or forage more effectively than shallower ones. Finally, even without tails attached, they still survived and thrived in their new environments.

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