Trunkhorse have a tan or brown body and an elongated blue and purple trunk used for grasping food. Young trunkhorses have pale yellow stripes that turn blue with age. These stripes provide camouflage from predators.
Males are slightly larger than females and possess a pair of tusks used for fighting with other males during the breeding season. Each foot has a small pair of claws whose size and function has been lost through evolution, but likely were longer and functioned for climbing in their ancestors.
Trunkhorses live on open plains in herds of 30-40 individuals, where they spend their time grazing or resting. The herd must cover vast areas of land to consume the quantity and diversity of vegetation needed to thrive. They occasionally enter forested regions to consume seasonal fruits, but rarely remain there for long because of greater risk from predators.
Trunkhorses consume almost any type of vegetation on the plains of Phygaris, as well as fruits that fall from trees bordering the plains. Their plate-like teeth grind the vegetation before swallowing, and a series of three stomachs provide a home for the diverse community of microorganisms that assist in digestion.
Trunkhorses reproduce sexually, with a male and female pairing for several seasons. The mating ritual begins with males calling and posturing to females. Once paired, the male and female copulate while trotting in a circle. This activity is thought to enhance the probability of internal fertilization. Females give birth to one (but rarely two) live young. Parents care for the young trunkhorse for up to a year, until it reaches a large enough size to defend itself from predators.
Trunkhorses appear highly intelligent, and often use their trunks to hold sticks with which they will knock fruits off of trees. This behavior may represent a form of culture that passes from parent to offspring through demonstration and practice.