Pigs possess four toes, or digits, on each foot, an anatomical feature they share with other even-toed ungulates like cows and deer. A single pig foot has four separate, hoofed structures attached. However, the physical structure is arranged so that not all four digits are used equally for standing and walking. The weight distribution focuses heavily on two central digits, while the other two remain elevated from the ground during normal locomotion.
The Four Digits of a Pig’s Foot
The pig’s foot is anatomically divided into two main, central digits (the third and fourth) and two smaller, accessory digits (the second and fifth). These central digits are the structures that form the cloven hoof, the defining characteristic of this group of mammals. The third and fourth digits are substantially larger and bear the vast majority of the animal’s weight when it is standing or moving on firm surfaces. Each of these two primary digits is fully developed and contains three phalangeal bones, which are the same bones that form the toes of many other vertebrates.
The smaller, accessory digits are positioned higher up the leg on the rear side of the foot and are commonly known as dewclaws. The pig is distinct from other even-toed ungulates because its dewclaws are not merely small vestigial structures. Both the metacarpal and phalangeal bones are present within a pig’s dewclaws, similar in structure to the weight-bearing digits. The two central hooves are protected by a hard, horny covering, while the sole beneath them is relatively small and soft. This unique structure allows the pig to walk on the tips of its two main toes, a form of locomotion known as unguligrade.
The Role of the Dewclaws
While the two central digits perform most of the work during normal walking, the dewclaws serve a specialized purpose for stability on irregular terrain. These smaller, elevated digits come into contact with the ground when the pig is navigating soft substrates, such as mud or deep sand. When the main hooves sink into a soft surface, the dewclaws splay out and press down, effectively enlarging the surface area of the foot. This action provides additional traction and prevents the pig from sinking too deeply.
A full set of bones within the dewclaws supports their function as an active part of the foot’s support mechanism. They act as stabilizers, especially when the pig is moving quickly or changing direction on uneven ground. While they may not bear weight when the pig is standing on a hard surface, their role in maintaining balance and mobility on challenging terrain makes them an integral part of the pig’s locomotion system.