In appearance, Arboreals were covered with hair (at least their hands and heads were) and had long, sharp fingernails, dark eyes, and a ridge running from their noses to the back of their heads. (ENT: "The Xindi", et al.) Arboreals were susceptible to a certain type of mutagenic virus created by the Loque'eque. (ENT: "Extinction") Arboreals had a dislike and perhaps even a fear of water. (ENT: "Countdown") However, they did drink beverages. Arboreals were considered to be lethargic by the other Xindi species. They were also extremely calm, even when taken hostage. (ENT: "The Shipment")