Behavioral Genetics and Animal Science - Genetics and the Behavior of Domestic Animals - page 3

generations and environmentally induced developmental events recurring during
each generation.”
Major behavioral differences exist between domesticated animals and their
wild relatives. For example, the jungle fowl is much more fearful of novel
objects and strange people compared to the domestic white Leghorn chicken
(Campler et al., 2009). A strong genetic component underlies differences in
fearfulness between jungle fowl and domestic chickens ( Agnvall et al., 2012 ).
Domestication may have been based on selection for tameness. In long-term
selection experiments designed to study the consequences of selection for the
“tame” domesticated type of behavior, Belyaev (1979) and Belyaev et al.
(1981) studied foxes reared for their fur. The red fox (Vulpes fulva) has been
raised on seminatural fur farms for over 100 years and was selected for fur traits
and not behavioral traits. However, the foxes had three distinctly different
behavioral responses to people. Thirty per cent were extremely aggressive,
60% were either fearful or fearfully aggressive and 10% displayed a quiet
exploratory reaction without either fear or aggression. The objective of this
experiment was to breed animals similar in behavior to the domestic dog.
By selecting and breeding the tamest individuals, 20 years later the experiment
succeeded in turning wild foxes into tame, border collie-like fox-dogs. The
highly selected “tame” population of (fox-dog) foxes actively sought human
contact and would whine and wag their tails when people approached ( Belyaev,
1979 ). This behavior was in sharp contrast to wild foxes which showed
extremely aggressive and fearful behavior toward man. Keeler et al.(1970)
described this behavior:
Vulpes fulva (the wild fox) is a bundle of jangled nerves. We had observed that
when first brought into captivity as an adult, the red fox displays a number of
symptoms that are in many ways similar to those observed in psychosis. They resemble
a wide variety of phobias, especially fear of open spaces, movement, white objects,
sounds, eyes or lenses, large objects, and man, and they exhibit panic, anxiety, fear,
apprehension, and a deep trust of the environment. They are 1) catalepsy-like frozen
positions, accompanied by blank stares, 2) fear of sitting down, 3) withdrawal,
4) runaway flight reactions, and 5) aggressiveness. Sometimes the strain of captivity
makes them deeply disturbed and confused, or may produce a depression-like state.
Extreme excitation and restlessness may also be observed in some individuals in
response to many changes in the physical environment. Most adult red foxes soon
after capture break off their canine teeth on the mesh of our expanded metal cage in
their attempts to escape. A newly captured fox is known to have torn at the wooden
door of his cage in a frenzy until he dropped dead from exhaustion.
Belyaev (1979) and Belyaev et al. (1981) concluded that selection for
tameness was effective in spite of the many undesirable characteristics asso-
ciated with it. For example, the tame foxes shed during the wrong season
and developed black and white patterned fur. Changes were also found in