Vai-sehlat were a type of animal lifeform that existed on the planet Vulcan.

Gene-engineered vai-sehlat were often ridden by soldiers on Vulcan during the chaotic times before the Time of Awakening. During travel through the deserts, there were many dangers one of which included finding the lair of a dormant vai-sehlat. (TOS - Vulcan's Soul novel: Exodus)

The menton of genetic engineering suggests that these creatures were an altered breed of sehlat.