Behavioral Genetics and Animal Domestication - Genetics and the Behavior of Domestic Animals - page 47

animals, though this will generally be due to selection for a specific pheno-
type, and will also often be closely related to inbreeding.
Selection
Selection can be further subdivided into artificial (both intentional and
inadvertent), natural, and relaxed in the case of domestic animals.
Artificial Selection
This can probably be thought of as both the strongest and most defining
mechanism of domestication ( Price and King, 1968 ). The effects of this can
be extremely rapid, and even within even just a few generations of selection,
large differences can occur. For example, both silver foxes ( Belyaev et al.,
1981, 1984 ) and rats ( Albert et al., 2008, 2009 ) selected for tameness show a
variety of behavioral and physiological responses after just a few genera-
tions, as discussed above. Chickens selected for differential growth show a
similar marked response to selection ( Carlborg et al., 2006 ). These are exam-
ples of intentional artificial selection, though unintentional artificial selection
can also occur. Examples of this would be the coonstripe shrimp, Pandalus
danae, inadvertently selected over 10 generations for a decrease in escape
tail-flip response (this response lead to injury during handling ( Marliave et al.,
1993 ) and for trout inadvertently selected for stress reduction to increase
fecundity ( Fevolden et al., 1991 ). One important difference to consider
between artificial and natural selection has been put forward by Price ( Price,
1999 ), in that artificial selection is “goal-oriented”, whereby individuals with
a desirable phenotype are then bred from (i.e. selection occurs prior to repro-
duction), whereas with natural selection an individual is only “assessed”
through its representation in future generations (i.e. the number of offspring
it produces).
Relaxed Selection
As mentioned above, certain behavioral adaptations, principally foraging
ability and predator avoidance, are no longer relevant to the survival of an
animal in captivity. In the case of antipredation behaviors in particular, there
are associated costs with exhibiting these traits and relaxed pressure may
therefore drive the traits in the opposite direction (especially considering that
wild populations with lower predation pressure exhibit these behaviors less).
( Kronenberger and Medioni, 1985 ) showed that domestic mice preferred
novel saccharin-water more than their wild counterparts. Such neophobia is
often seen in wild-derived populations, but less so in domestic populations
( Sch ¨ tz et al., 2001; Wright et al., 2006c ).
This relaxation of selection could be expected to lead to an increase in
phenotypic and genetic variability, however this is often confounded with