Tra'cors were the amphibious cousins of the rancor native to Socorro. Though smaller and almost completely waterbound, tra'cor shared most of the rancor's traits, including its hostile temperament.

While the tra'cor could survive on the underwater grasses and mosses of Socorro, they would consume meat whenever the opportunity presented itself, waiting within Socorro's water cellars to trap mutriok and other creatures that came to drink.

Tra'cors could also move on land, but remaining out of water for more than 24 hours would result in severe dehydration. They were rarely caught on land long enough to die of dehydration, however, as they were equipped with special glands on their necks that allowed them to locate nearby water sources. In fact, tra'cors often migrated across land from one water pool to another when it was necessary to find a new grotto.

Tra'cors rarely lived in groups of more than two or three, although most were usually solitary.