Herbivore is one of the four ecological roles. A player chooses an ecological role for their species at empire creation, and all creatures on a planet fit into one of the four ecological roles. Herbivores may be domesticated by building farms producing animal products. Herbivores may also be ridden by players by walking up to them and pressing your mount key (default E).
Herbivores may eat all plant-based foods. They may not eat meat products.
Herbivore behavior varies. Some may be docile while others may be extremely aggressive and dangerous. This depends on the particular species.