Behavioral development in animals undergoing domestication

The process of domestication involves adaptation, usually to a captive envi ronment. Domestication is attained by some combination of genetic changes o ccurring over generations and developmental mechanisms (e.g., physical matu ration, learning) triggered by recurring environmental events or management practices in captivity that influence specific biological traits. The tran sition from free-living to captive status is often accompanied by changes i n availability and/or accessibility of shelter, space, food and water, and by changes in predation and the social environment. These changes set the s tage for the development of the domestic phenotype. Behavioral development in animals undergoing domestication is characterized by changes in the quan titative rather than qualitative nature of responses. The hypothesized loss of certain behavior patterns under domestication can usually be explained by the heightening of response thresholds. Increases in response frequency accompanying domestication can often be explained by atypical rates of expo sure to certain forms of perceptual and locomotor stimulation. Genetic chan ges influencing the development of the domestic phenotype result from inbre eding, genetic drift, artificial selection, natural selection in captivity, and relaxed selection. Experiential contributions to the domestic phenotyp e include the presence or absence of key stimuli, changes in intraspecific aggressive interactions and interactions with humans. Man's role as a buffe r between the animal and its environment is also believed to have an import ant effect on the development of the domestic phenotype. The domestication process has frequently reduced the sensitivity of animals to changes in the ir environment, perhaps the single-most important change accompanying domes tication. It has also resulted in modified rates of behavioral and physical development. Interest in breeding animals in captivity for release in natu re has flourished in recent decades. The capacity of domestic animals to su rvive and reproduce in nature may depend on the extent to which the gene po ol of the population has been altered during the domestication process and flexibility in behavioral development. "Natural" gene pools should be prote cted when breeding wild animals in captivity for the purpose of reestablish ing free-living natural populations. In some cases, captive-reared animals must be conditioned to Live in nature prior to their release. (C) 1999 Else vier Science B.V. All rights reserved.