Improving the Adaptability of Animals by Selection - Genetics and the Behavior of Domestic Animals - page 290

selection was probably the main cause of genetic change. This means that
animals showing low levels of adaptation to the new, man-made conditions
had poorer fitness and their genes were eliminated from the gene pool of the
next generation ( Faure et al., 1992 ). This type of selection is likely to be
efficient only when a high proportion of animals are carrying genes of low
value in the new artificial environment. For example, animals with high fear
and a flighty, nervous temperament may be so stressed that they fail to breed
in captivity. Subsequently, the failure of these animals to breed in captivity
probably resulted in natural selection for lower levels of fearfulness. During
the early stages of domestication, farmers were able to recognize individual
traits in their animals and prevented most animals exhibiting undesirable
characteristics from reproducing. For example, a very aggressive bull which
endangered the farmer would probably be culled. When flocks or herds
become too large to allow recognition of individual animals, this method
was no longer applicable. For both practical and economic reasons, animal
breeding was subsequently concentrated on specific traits, irrespective of
their relationships to other traits or concerns for animal welfare.
A more sensible solution would be to select for general adaptability and
characteristics that are expressed in a wide variety of environments. High
appetite is an example of a trait that can be expressed in a wide range of envir-
onments; environmental change cannot mask the effects of genetic selection.
On the other hand, perching is a behavior that can only be expressed in certain
environments. Obviously, perching behavior cannot be expressed if perches
are not available. Faure and Jones (1982a, b) found that perching behavior
of chickens differs between strains. This suggests that it should be possible to
select lines with high and low levels of perching behavior. Although selection
for low levels of perching behavior might improve the adaptation of domestic
hens to battery cages, if floor pens or aviaries are used it might be advanta-
geous to promote high levels of perching behavior ( Appleby et al., 1988 ).
Either type of selection would lead to very specialized lines of chickens which
would be undesirable given the diversity of modern husbandry systems.
We chose to select for two characteristics which are indicators of general
adaptability and are behaviorally expressed in most environments: fear and
social reinstatement behavior (see Chapter 2 for further information on fear).
Social reinstatement is the tendency of animals to flock and stay close to
conspecifics (flockmates). Fear and social motivation are basic motivational
systems in a wide variety of species. We chose to use Japanese quail as a
model of other species.

SELECTION PROCEDURE
The measurement of behavioral traits is often very time consuming, and
selection requires behavioral measures of large numbers of animals ( Faure,
1981 ). Therefore, we chose to use relatively short tests (no longer than