Precociality and altriciality

Precocial young have open eyes, hair or down, large brains, and are immediately mobile and somewhat able to flee from or defend themselves against predators.

[9] Black mambas are highly precocial; as hatchlings, they are fully independent, and are capable of hunting prey the size of a small rat.

[13] In birds and mammals altricial species are those whose newly hatched or born young are relatively immobile, lack hair or down, are not able to obtain food on their own, and must be cared for by adults; closed eyes are common, though not ubiquitous.

[14] For example, newborn domestic cats cannot see, hear, maintain their own body temperature, or gag, and require external stimulation in order to defecate and urinate.

The word “altriciality” is derived from the Latin root alere, meaning "to nurse, to rear, or to nourish", and indicates the need for young to be fed and taken care of for a long duration.

Examples of precocial birds include the domestic chicken, many species of ducks and geese, waders, rails, and the hoatzin.

Precocial birds can provide protein-rich eggs and thus their young hatch in the fledgling stage – able to protect themselves from predators and the females have less post-natal involvement.

Altricial birds are less able to contribute nutrients in the pre-natal stage; their eggs are smaller and their young are still in need of much attention and protection from predators.

It may be that altricial strategies in mammals, in contrast, develop in species with less migratory and more territorial lifestyles, such as Carnivorans, the mothers of which are capable of bearing a fetus in the early stages of development and focusing closely and personally upon its raising, as opposed to precocial animals which provide their youths with a bare minimum of aid and otherwise leave them to instinct.

Infants are born with minimal eyesight, compact and fleshy bodies, and "fresh" features (thinner skin, small noses and ears, and scarce hair if any).