Altricial and Precocial

The terms altricial and precocial are perhaps most often applied to bird species, but can also be applied to any species of animal. The differences are based on how the young of a species act after their birth or hatch.

Altricial

Altricial chicks in the nest. Note the closed eyes, lack of feathers, and inability to feed themselves

This term is used to refer to species that are heavily reliant on their parent(s) after birth, frequently being incapable of moving quickly independently and also sometimes being born with eyes shut tight. It is also far from unusual for the young of this type to be unable to regulate their body temperature effectively, or feed themselves. Since altricial young are born so helpless, they rely on their parent(s) for food, warmth, protection, and a number of other needs. Here are some more altricial species:

Humans

Dogs

Rats

Precocial

A precocial chick. Note the full set of feathers and open eyes

Species of this type are quite independent or "precocious" at birth. They are usually capable of walking and running very quickly, within a few hours. In some species, they still need some help in regulating their body temperature and feeding themselves. However, other species are completely on their own from birth. Here are some more precocial species:

Elephants

Horses

Guinea pigs

Source is Stanford University. Images are from Wikimedia Commons and are under Creative Commons licenses or are copyright free: one, two, three, four, five, six, seven, eight.