In biology

Biology

Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial

Altricial

Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...

," where the young are born or hatched helpless. Extremely precocial species may be called "superprecocial

Superprecocial

The term superprecocial refers to a level of physical maturity and capability in young animals that is most extreme. Examples are the Megapode birds, which have full flight feathers and which, in some species, can fly on the same day they hatch from their eggs...

." These three categories form a continuum, without distinct gaps between them. Precocial species are normally nidifugous

Nidifugous

Nidifugous organisms are those that leave the nest shortly after hatching or birth. It is derived from Latin nidus for "nest" and fugere meaning "to flee". The terminology is most often used to describe birds and was introduced by Lorenz Oken in 1916...

, meaning that they leave the nest shortly after birth or hatching.

The span between precocial and altricial species is particularly broad in bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s. Precocial birds are born with their eyes open. They are covered with downy feathers that soon grow to adult feathers after hatching. These kind of birds can also swim and run much sooner after their birth than other birds, such as songbirds. Very precocial birds can be ready to leave the nest in a short period of time following hatching (e.g. 24 hours). Many precocial chicks are not independent in thermoregulation

Thermoregulation

Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...

 (the ability to regulate their own body temperatures), and they depend on the attending parent(s) to brood them with body heat for a short period of time. Precocial birds find their own food, sometimes with help or instruction from the parents. Examples of precocial birds include the domestic chicken

Chicken

The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...

, many species of duck

Duck

Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...

s and geese

Goose

The word goose is the English name for a group of waterfowl, belonging to the family Anatidae. This family also includes swans, most of which are larger than true geese, and ducks, which are smaller....

, wader

Wader

Waders, called shorebirds in North America , are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas , gulls , terns , skimmers , and auks...

s, rails and the Hoatzin

Hoatzin

The Hoatzin , also known as the Hoactzin, Stinkbird, or Canje Pheasant, is a species of tropical bird found in swamps, riverine forest and mangrove of the Amazon and the Orinoco delta in South America...

. The most extreme, superprecocial

Superprecocial

The term superprecocial refers to a level of physical maturity and capability in young animals that is most extreme. Examples are the Megapode birds, which have full flight feathers and which, in some species, can fly on the same day they hatch from their eggs...

 birds are the megapodes, where the newly-hatched chicks dig themselves out of the nest mound without parental assistance, and fly on the first day after hatching.

Precociality is found in many other animal groups. Familiar examples of precocial mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s are most ungulate

Ungulate

Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving. They make up several orders of mammals, of which six to eight survive...

s, the guinea pig

Guinea pig

The guinea pig , also called the cavy, is a species of rodent belonging to the family Caviidae and the genus Cavia. Despite their common name, these animals are not in the pig family, nor are they from Guinea...

, and most species of hare

Hare

Hares and jackrabbits are leporids belonging to the genus Lepus. Hares less than one year old are called leverets. Four species commonly known as types of hare are classified outside of Lepus: the hispid hare , and three species known as red rock hares .Hares are very fast-moving...

. This last example demonstrates that precociality is not a particularly conservative characteristic, in the evolutionary sense, since the closely related rabbit

Rabbit

Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...

 is highly altricial

Altricial

Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...

.

Precocial species typically have a longer gestation

Gestation

Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

 or incubation period than related altricial species, and smaller litters or clutches, since each offspring has to be brought to a relatively advanced (and large) state before birth or hatching.

The phenomenon of imprinting

Imprinting (psychology)

Imprinting is the term used in psychology and ethology to describe any kind of phase-sensitive learning that is rapid and apparently independent of the consequences of behavior...

 studied by Konrad Lorenz

Konrad Lorenz

Konrad Zacharias Lorenz was an Austrian zoologist, ethologist, and ornithologist. He shared the 1973 Nobel Prize with Nikolaas Tinbergen and Karl von Frisch...

 is characteristic of precocial birds.

Etymology

The word "precocial" is derived from the same root as precocious, implying in both cases early maturity.

Phylogeny

Precociality is thought to be ancestral in birds. Thus, altricial birds tend to be found in the most derived groups. There is some evidence for precociality in Protobird

Protobird

"Protobird" is an informal term that has been used by some paleontologists when discussing animals that, while technically classified as non-avian dinosaurs, possess many features normally associated with birds. All protobirds are extinct....

s (Elzanowski, 1995.) and Troodontids (Varricchio et al. 2002).

Notations

• Starck J.M., Ricklefs R. E. Patterns of Development: The Altricial - Precocial Spectrum. In; Avian Growth and Development. Oxford University Press
  Oxford University Press
  Oxford University Press is the largest university press in the world. It is a department of the University of Oxford and is governed by a group of 15 academics appointed by the Vice-Chancellor known as the Delegates of the Press. They are headed by the Secretary to the Delegates, who serves as...
  
  , New York, NY, 1998.