Why Do Warthogs Have Warts? What the Bumps Really Are

What warthog warts really are

The bumps on a common warthog’s face are normal body parts, present on every adult warthog. They are made of thickened skin over dense, cartilage-like connective tissue, with no bone inside. They develop as the animal grows, and in older males they become very prominent.

Biologists describe up to three sets of facial bumps:

• Below the eyes (suborbital warts): the largest pair, which in big males can reach about 15 cm (6 in) long.
• Between the eyes and tusks (preorbital warts): a second pair, well developed in males but small or barely visible in females.
• Along the jaw (submaxillary warts): small bumps on the lower jaw that carry pale, bristly whiskers.

Human warts, by contrast, are small growths caused by human papillomavirus. Warthogs got their name only from the look of the bumps.

Protection during fights

Male warthogs compete for females during the breeding season. A typical fight is a ritual shoving match: two boars face each other, lower their heads and push, twist and strike with their heads and blunt upper tusks. The sharp lower tusks are rarely used against rivals, and serious injuries are uncommon.

The large warts lie exactly where a rival’s head and tusks strike, beside the eyes and along the face. Acting like built-in padding, they help protect the eyes and jaw from blows. This explains why the warts are biggest in adult males, the sex that fights, and much smaller in females.

A signal of size and strength

The warts probably also work as a visual signal. Because they grow larger as a male matures, a boar with big warts and long tusks is likely to be an older, stronger animal. Rivals can judge each other before a fight escalates, and females may also notice these features.

This kind of trait, where males develop exaggerated features for competition, is called sexual dimorphism. Other examples include the mane of a lion and the antlers of deer.

When do warthogs get their warts?

Newborn piglets have smooth faces with no obvious warts. The bumps start to show as young warthogs grow, and in males they keep enlarging for years along with the tusks. By the time a boar is old enough to win females, at around four years old, his face is usually clearly knobby. Females develop only small bumps that change little after they reach adult size.

This timing fits the idea that the warts are mainly a tool for adult males. Young males in bachelor groups play-fight and spar, but serious contests over females come later, when the warts are fully grown.

Common myths about warthog warts

Myth: the warts are a disease or infection. They are healthy, normal structures found on every adult warthog.

Myth: warthogs can pass warts to people. Warthog warts are not caused by a virus and are not contagious.

Myth: the warts are for digging. Warthogs dig with their snouts and feet; the warts sit on the sides of the face, where they guard against blows.

How to tell male and female warthogs apart

On safari, the quickest way to sex a warthog is to look at the face: a big, knobby face with heavy tusks belongs to a male.

Tusks and their uses

Warthog tusks are enlarged canine teeth that grow throughout life. The upper tusks curve up and outward and can exceed 25 cm (10 in) in big males. The lower tusks are much shorter, but every time the warthog opens and closes its mouth they rub against the upper tusks, which keeps them razor sharp.

Warthogs use their tusks mainly for:

• Fighting rivals: mostly with the blunt upper tusks during shoving contests.
• Defense: the sharp lower tusks can cause serious wounds to predators such as lions, leopards and hyenas.
• Marking: warthogs rub their tusks and nearby glands on trees and posts to leave scent marks.

Contrary to a common belief, warthogs do not dig mainly with their tusks. They use their tough, flat snout and their feet to root up grass bases, bulbs and rhizomes. See What do warthogs eat? for more on how they feed.

Other wild pigs with warts

Warthogs are not the only pigs with facial bumps. Several warty pigs of Southeast Asia, such as the Javan warty pig and the Visayan warty pig, also have warts on the face, and in these species too the bumps are largest in males. This pattern suggests that facial padding has evolved more than once in pigs that fight head to head.

The domestic pig and wild boar have no such large warts, but wild boar males do develop a thick shield of skin and tissue over the shoulders, which protects them in fights in a similar way.