Genetics of Domesticated Behavior in Dogs and Foxes - Genetics and the Behavior of Domestic Animals - page 370

course of animal domestication. He further hypothesized that selection for an
unusual behavior in wild species, that is, a tame response to humans, may
affect many physiological processes in animals under selection (i.e. activity
of hypothalamic-pituitary-adrenal axis) and lead to the emergence of varia-
tion in morphology, a common feature of domesticated species ( Belyaev,
1979; Belyaev and Trut, 1989; Trut 1988 ). The fox was selected as a model
to test this hypothesis.
When the fox domestication experiment began, foxes had been bred in
captivity for over 50 years. Fox-fur farming was pioneered on Prince
Edward Island in Southeastern Canada, beginning in the 1890s ( Westwood
1989 ). Farmers on Prince Edward Island primarily raised the silver black

coat color variant of red foxes, which had the greatest economic value and
were subsequently used to stock fur farms in many areas of North America
and Eurasia ( Bespyatih, 2009; Nes et al., 1988; Westwood 1989; Petersen
1914 ). Mitochondrial DNA analysis has identified Eastern Canada as the pri-
mary, if not sole, source of ancestry for farm-bred fox populations main-
tained at the ICG in Novosibirsk ( Statham et al., 2011 ).

SELECTION OF FOXES FOR TAME BEHAVIOR
In the beginning of the experiment, 130 foxes that showed less fearful and
aggressive responses to humans were identified at several commercial fox
farms across the former Soviet Union and brought to the experimental farm
at the ICG to become the founders for the experimental population. The
response to human presence was the sole selection criteria in this population.
At first the selection was focused against aggressive responses to humans, as
summarized in Trut et al., 2004 :

The main task at this stage of selection was eliminating defensive reactions to
humans. In order to reveal variability in the expression of these reactions more
completely, the animals in the selected population were subjected to more intensive
contacts with humans than in usual practice. During these contacts, the pups were
subjected to a number of tests: the experimenter attempted to hand feed, stroke or
handle them. This type of human animal communication continued for the first three
to four months of life of the animals. As a result, the emotionally negative defensive
reactions to humans in these foxes weakened, disappeared or, in some of the
animals, emotionally positive reactions were formed. The foxes that retained
aggressive fearful reactions to humans in spite of the 3-month period of human
contacts with them, were eliminated by selection from the population as soon as in
2 to 3 generations ( Trut, 1980a, 1980b; Trut, 1999 ). In generation 4 of selection, the
first pups appeared that did not form aggressive fearful reactions to humans as a
result of positive contacts with them. On the contrary, these pups demonstrated
emotionally positive response to humans: when the experimenter approached them,
they whined and wagged their tails anticipating a positive contact.