The Male Tail: Animal Mating and Human Anatomy

Tails in the animal kingdom serve purposes from locomotion to communication. For some species, however, the “male tail” is not a tool for survival but an elaborate ornament for reproduction. This specialized function highlights an evolutionary story where attracting a mate becomes more important than navigating the environment.

Diversity of Male Tails in the Animal Kingdom

In many species, the male possesses a tail that is different from the female’s, a distinction known as sexual dimorphism. This is often visible in the tail’s size, shape, and coloration. The peacock is a well-known example; the male’s train of elongated feathers can measure over five feet long. These feathers are adorned with iridescent ocelli, or eyespots, that create a bright display when fanned out.

This phenomenon is not limited to birds. The male guppy sports a tail fin that is significantly larger and more ornate than the female’s, decorated with a mosaic of bright spots. Similarly, some male lizards, such as certain species of anoles, have developed colorful and elongated tails that they use in displays.

The bird kingdom offers a wide variety of such specialized tails. Male birds-of-paradise have evolved an assortment of tail feathers, from long filaments to broad plumes showcased during courtship dances. Another example is the Long-tailed Widowbird of Africa, where the male grows a tail that can be more than double its body length, a feature absent in the female.

The Purpose Behind Male Tails

The evolution of these elaborate male tails is driven by sexual selection, a process where success is determined by securing a mate, not just survival. In many species, female preferences shape the physical traits of males over generations. A male’s large tail acts as an advertisement, signaling his genetic quality to potential partners.

Ornamental tails can be honest indicators of a male’s fitness because growing and maintaining them requires significant energy. A male who can sport such an appendage proves he is healthy and well-fed. For instance, a peacock with a large train is signaling that he can thrive despite the aerodynamic challenges and increased predation risk from his plumage.

Beyond attracting females, these tails can factor into male-male competition, with larger tails used in displays to intimidate rivals and signal dominance. The bright colors and unique patterns also serve as a form of species recognition. This ensures that individuals mate with members of their own species, which is important in environments where similar species coexist.

Do Human Males Have Tails?

Modern humans do not possess external, functional tails. The structure commonly called the “tailbone” is scientifically known as the coccyx. This is a vestigial structure, meaning it is a remnant of an anatomical feature that was functional in our distant ancestors.

The coccyx is composed of three to five fused vertebrae at the base of the spine and is present in both males and females. There is no “male tail” in humans that exhibits the sexual dimorphism seen in other animals. The coccyx serves as an attachment point for muscles and ligaments, but it does not extend externally or function in mating displays.

Our primate ancestors used their tails for balance while navigating life in the trees. As hominins adapted to a terrestrial, bipedal lifestyle, the need for a tail for balance diminished. Over millions of years, the external tail was lost, leaving the internal coccyx as a reminder of our evolutionary past. Infants are occasionally born with a small tail-like appendage, but these are rare and removed shortly after birth.