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(of hatchlings) naked and blind and dependent on parents for food

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/01/27 09:31:32」(JST)

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Altricial young birds.

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. The word is derived from the Latin root alere meaning "to nurse, to rear, or to nourish" and refers to the need for young to be fed and taken care of for a long duration.^[1] Species whose young are immediately or quickly mobile are known as precocial.

Scope

In bird and mammal biology, altricial species are those species whose newly hatched/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. Altricial young are born helpless and require care for a specific amount of time. Among birds, these include herons, hawks, woodpeckers, owls, cuckoos and most passerines. Among mammals, marsupials and most rodents are altricial. Cats, dogs, and humans are some of the best-known altricial organisms.^[2]

At the opposite end of the spectrum are precocial animals in which the young have open eyes, have hair or down, have large brains, and are immediately mobile and somewhat able to flee from, or defend themselves against, predators. For example, with ground-nesting birds such as ducks or turkeys, the young are ready to leave the nest in one or two days. Among mammals, most ungulates are precocial, being able to walk almost immediately after birth. Beyond the precocial are the superprecocial animals, such as the megapode birds, which hatch with full flight feathers.^[3]

Basis

Different animals employ different precocial and altricial strategies; there is no clear distinction between the two states, and a wide range of intermediate states.^[1] The ability of the parents to obtain nutrition and contribute to the pre-natal and post-natal development of their young appears to be associated.

Precocial birds are able to provide protein-rich eggs and thus their young hatch in the fledgling stage – able to protect themselves from predators (ducks or turkeys) and the females have less involvement post-natal. Altricial birds are less able to contribute nutrients in the pre-natal stage; their eggs are smaller and their young still in need of much attention and protection from predators. This may be related to r/K selection; however, this association fails with a number of cases.^[4]

In the case of mammals it has been suggested that large adult body sizes favor production of large, precocious young, which develop with a long gestation period. Large young may be associated with long lifespan, extended reproductive period, and reduced litter size. It has been suggested that altricial strategies in mammals may be favoured if there is a selective advantage to mothers that are capable of resorbing embryos in early stages of development.^[5] Some niches require young to be precocial for survival, such as cetaceans: restricted to water, and immobile, their helpless young would quickly drown.

Terminology

In birds, the terms Aves altrices and Aves precoces was introduced by Carl Jakob Sundevall (1836) and the terms nidifugous and nidicolous by Lorenz Oken in 1816. The two classifications were considered identical in early times, but the meanings are slightly different, in that "altricial" and "precocial" refer to developmental stage, while "nidifugous" and "nidicolous" refer to leaving or staying at the nest.^[4]

The two strategies result in different brain sizes of the newborns compared to adults. Precocial animals' brains are large at birth relative to their body size, hence their ability to fend for themselves. However, as adults, their brains are not much bigger or more able. Altricial animals' brains are relatively small at birth, thus their need for care and protection, but their brains continue to grow. As adults, altricial animals end up with comparatively larger brains than their precocial counterparts. Thus the altricial species have a wider skill set at maturity.^[1]

References

^ ^a ^b ^c Ehrlich, Paul (1988). The Birder's Handbook. New York: Simon & Schuster. ISBN 0-671-65989-8. ^{[page needed]}
^ Arterberry, Martha E. (2000). The Cradle of Knowledge. Development of Perception in Infancy. Cambridge: MIT Press. p. 27. ISBN 9780262611527.
^ Starck, J.M., Ricklefs, R.E. (1998). Avian Growth and Development. Evolution within the altricial precocial spectrum. New York: Oxford University Press. ISBN 0-19-510608-3.
^ ^a ^b Starck, J. (1998). Avian Growth and Development. Oxford Oxfordshire: Oxford University Press. ISBN 0-19-510608-3. ^{[page needed]}
^ Eisenberg, John (1981). The Mammalian Radiations. London: Athlone Press. ISBN 0-485-30008-7. ^{[page needed]}

External links

The altricial-precocial spectrum in birds

English Journal

Development of vocalization and hearing in American mink (Neovison vison).

Brandt C, Malmkvist J, Nielsen RL, Brande-Lavridsen N, Surlykke A.SourceNewcastle University;
The Journal of experimental biology.J Exp Biol.2013 Jun 20. [Epub ahead of print]
American mink (Neovison vison) kits are born altricial and fully dependent 40 on maternal care, for which the kits' vocalisations appear essential. We used Auditory Brainstem Recording (ABR) to determine (1) hearing sensitivity of adult females from two breeding lines known to differ in maternal beh
PMID 23788707

Assessing effects of environmental chemicals on neuroendocrine systems: Potential mechanisms and functional outcomes.

Ottinger MA, Carro T, Bohannon M, Baltos L, Marcell AM, McKernan M, Dean KM, Lavoie E, Abdelnabi M.SourceDepartment of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, United States. Electronic address: maotting@umd.edu.
General and comparative endocrinology.Gen Comp Endocrinol.2013 Jun 15. pii: S0016-6480(13)00269-4. doi: 10.1016/j.ygcen.2013.06.004. [Epub ahead of print]
Environmental pollutants encompass a vast array of compounds. Most studies in birds have focused on toxicological effects, with little attention to non-lethal effects. Consequently, it has proven difficult to assess potential risk associated with exposure to endocrine disrupting chemicals (EDCs). As
PMID 23773971

Postnatal epigenetic reprogramming in the germline of a marsupial, the tammar wallaby.

Suzuki S, Shaw G, Renfree MB.SourceDepartment of Zoology, The University of Melbourne, Victoria, 3010, Australia. ssuzuki@shinshu-u.ac.jp.
Epigenetics & chromatin.Epigenetics Chromatin.2013 Jun 3;6(1):14. doi: 10.1186/1756-8935-6-14.
BACKGROUND: Epigenetic reprogramming is essential to restore totipotency and to reset genomic imprints during mammalian germ cell development and gamete formation. The dynamic DNA methylation change at DMRs (differentially methylated regions) within imprinted domains and of retrotransposons is chara
PMID 23732002

Japanese Journal

幼獣の人工哺育が人馴れに与える影響およびその予防と矯正

黒滝恭衣,平山加奈子,木俣美枝子 [他]
共生社会システム研究 4(1), 264-277[含英語文要旨], 2010-07
NAID 40017263910

飼育下のカナダカワウソの外部形態計測値：新生獣と成獣のプロポーションの比較

清田雅史,吉川尚基,大野豊,香山薫,中島将行
哺乳類科学 49(2), 269-275, 2009
箱根園水族館で飼育されたカナダカワウソLontra canadensisの体各部の外部計測値を集計し，体長に対する各部のプロポーションを成獣5頭と新生獣1頭の間で比較した．新生獣の頭，口や体前部は成獣に比べ相対的に大きかったが，手掌，後肢，尾は小さかった．同亜科に属するラッコと比べるとカナダカワウソの遊泳に関わる部位は異なった発育パターンを示し，ラッコは仔獣の前肢が大きく後肢や尾の相対サイズに成獣 …
NAID 130000885764