Genetics and Behavior During Handling, Restraint, and Herding - Genetics and the Behavior of Domestic Animals - page 134

simple. The Agouti has two alleles “A” Agouti, and “a” non-Agouti.
Dominant “A” produces the banding of hair we recognize as Agouti.
Recessive “a” produces solid colored hairs. Many coat color mutations
appear in Agouti rats bred in captivity: albino, black, hooded, and others. In
a population of rats bred in captivity for 35 generations, Keeler (1947) noted
that some of these mutations were associated with varying degrees of tame-
ness. Black rats were much tamer than the agoutis. They described the black
rats as “Already tame by nature. If very excited they may click their teeth,
but are not apt to bite.” They conclude that the strain of tame albino rat
(homozygous for black and hooded), “was not domesticated by painstaking
selection over long periods of time, but was modified in morphology princi-
pally by the introduction of three coat color genes [albino, hooded, and
black], and in behavior principally by the (non-agouti) black gene.” Breeding
for the black non-agouti coat color in rats resulted in tamer, easier to handle
rats ( Keeler, 1942 ). In foxes, graded differences in temperament were found
between foxes selected for different coat colors ( Keeler, 1975; Keeler et al.,
1968 ). Foxes that were all raised in the same wooded compound had flight
zone differences

that ranged from silvers (200 yards), to platinums

(100 100 yards). It is interesting to note that the

foxes became progressively tamer as more and more mutant coat color genes
were added. Tameness was also highly correlated with adrenal gland
weights. The size of the adrenal gland decreased and the body weight
increased as the foxes became tamer. The animals with the most mutant
coat-color genes were the tamest.
Trut et al. (1997) selected wild agouti rats for tameness for over 30 gen-
erations. In the beginning of the experiment, white patches of hair began to
appear on the rats and increased until about 73% of the rats had white bel-
lies. Over time, the white patches on the piebald rats grew larger and larger.
In sum, selection for tameness correlated with the frequency and extent of
depigmentation.
Genetic selection for body traits has an effect on behavioral traits, and
selection for behavioral traits leads to changes in body traits ( Belyaev,
1979 ). Coat color and behavior are connected via a common biochemical
synthesis pathway of the pigments determining color—the melanins—and
the catecholamide group of neurotransmitters forming the basis of the infor-
mation processing system ( Hemmer, 1990 ). In artificial selection studies con-
ducted for the U.S. Department of agriculture on over 34,000 guinea pigs,
Wright (1978) showed that selecting for different hair colors changed many
other characteristics. This early research revealed patterns of associated
changes in body shape, relative size of certain internal organs, and changes
in temperament. In many cases, coat color can be used as a genetic marker
for such traits ( Keeler, 1975 ). Coat color is associated with differences in
physiology, morphology, and behavior in foxes ( Belyaev, 1979; Keeler
et al., 1968; Trut, 1999 ), guinea pigs ( Wright, 1978 ), Cocker Spaniel dogs

200 yards), to ambers (3