Behavioral Aspects of Animal Domestication

Since the survival and well-being of humankind is so inextricably bound to our domestic animals and plants, it is important that we understand the domestication process and its biological consequences. The objective of this review is to discuss available information on the biological basis of animal domestication, with particular emphasis on behavior. Domestication concerns adaptation, which is usually to a captive environment and which is achieved by some combination of genetic changes occurring over generations, as well as by environmentally induced changes in development that recur during each generation. Genetic changes will occur in population of organisms undergoing domestication as a result of both chance and of any shift in selection pressures accompanying the transition from nature to captivity. In addition to changes in gene frequencies, adaptation to the captive environment may be facilitated by certain recurring environmental events or management practices that influence the development of specific biological traits. It is difficult to generalize about the effects of domestication on either genetic or phenotypic variability because of different selection pressures on different traits and species. However, it is apparent that, with respect to animal behavior, domestication has influenced the quantitative rather than qualitative nature of the response. The postulated loss of certain behavior patterns under domestication can usually be explained by a heightening of response thresholds above normal levels of stimulation. Conversely, lowered thresholds of response often can be accounted for by constant exposure to certains forms of stimulation. Certain behaviors may have been altered because of man's role as a buffer between the animal and its environment. One of the more important behavioral changes accompanying the domestication process is a reduction in responsiveness to changes in the animal's environment. Food provisioning and man's control over the breeding process have reduced competition for important resources, and thus have permitted selection for the retention of juvenile characteristics (neotony). Feralization is the domestication process in reverse. The capacity of domestic animals to survive in nature may depend on the extent to which the gene pool of the population has been altered during the domestication process. "Natural" gene pools should be protected when breeding wild animals in captivity for the purpose of reestablishing free-living natural populations.