You can identify the age of a baby cottontail rabbit by noting a few of its characteristics and behaviors. A baby cottontail rabbit can sometimes be found alone without its mother in the wild. Mother cottontail rabbits leave the baby rabbits during the day and only return to feed them at night. Baby cottontail rabbits are extremely difficult to raise in captivity without the presence of their mothers. If you find a baby cotton tail rabbit alone, call a local wildlife rescue organization.
View the baby cottontail rabbit and note its characteristics and behaviors.
Weigh the rabbit. Newborn cottontail rabbits can weigh between 1 and 1.4 ounces. They can weigh between 3 and 5 ounces when they venture out of the nest at between 15 and 20 days old.
View the rabbit's fur. A newborn rabbit will have little to no hair. A rabbit that is around 14 days old will have a complete coat.
Check the baby cottontail rabbit's ears. A baby's ears are closed between 1 and 7 days old. The ears become erect between the age of 9 and 13 days.
View the rabbit's eyes. The eyes of a baby cottontail rabbit open between 5 and 7 days after birth.
Note the baby's reaction to loud noises. If a baby cottontail rabbit is nervous and jumpy in response to sudden noises, it is at least 21 days old.