Most herbivore animals can sustain Themself by foraging grass. Each time a roll for "Wandering Encounter" may occur if that die land on a 1, Rabbits will feel hungry (other species may require more roll to feel hungry). And then depending on food availability they will need to forage a certain amount of minute to fill their hunger
10 Minutes: Food is Common
20 Minutes: Food is Uncommon
30 Minutes: Food is Scarce

If the hungry animal have not eat and a "Skill check" or "Wandering Encounter" roll land on a 1
then they will incur 1 HP Damage

Note: that other non-rabbit species don't usually need to forage as much
hence they may not be worried to forage while traveling

Note: as covered in the Constitution page, rabbits may also eat their own Cacotropes both satisfying their hunger and recover 1 HP

From the playable speicies
Herbivore: Rabbit, Jackrabbit, Chipmunk, Squirrel, Porcupine (Occasional Insectivore)
Omnivore: Raccoon, Skunk, Opossum
Insectivore: Armadillo (they also eat Earthworms)