Genetics of Domesticated Behavior in Dogs and Foxes - Genetics and the Behavior of Domestic Animals - page 366

environment in a systematic manner. There are almost no dog studies that
take into account developmental aspects of behavior and the dogs' life
experiences ( Coppinger and Coppinger, 2001 ). One exception stands out: the
long-term study of dog behavior conducted at Jackson Laboratory in Bar
Harbor in the mid-20th century ( Scott and Fuller, 1965 ).
THE BAR HARBOR EXPERIMENT
In this 13-year-long study in Bar Harbor, the behavior of five different dog
breeds (Basenji, Beagle, Cocker Spaniel, Shetland Sheepdog, and Wire-haired
Fox Terrier) was studied in great detail from birth to approximately one year
of age. The experiment was designed to gain insight into the genetics of social
behavior; the dog was selected as a model because dog social behavior was
regarded as resembling human behavior, and there was a large amount of vari-
ation in behavior among the dogs ( Hahn and Wright, 1998; Scott and Fuller,
1965 ). The results of this experiment had a profound effect not only on our
understanding of dog behavior but on other disciplines including human psy-
chology, genetics, and evolutionary biology. Here we describe a few of the
Bar Harbor experiments and findings as examples that clearly illustrate the
complexity of dog behavior and the necessity of applying a systematic
approach for understanding basic biological principles underlying it.
A detailed analysis of canine behavioral development from the early
postnatal period identified a critical period in dog socialization ( Freedman
et al., 1961 ). The importance of this discovery to the field of dog behavior is
paramount. The role of the environment during the socialization period was
subsequently shown to be important for the development of other aspects of
dog behavior, such as herding behavior ( Coppinger and Coppinger, 2001 ).
Analysis of social relationships among littermates revealed different
behavioral mechanisms of aggression. By 11 weeks of age, 95% of litters
developed a food-related dominance hierarchy. Fox terriers formed more
dominance relationships than cocker spaniels or beagles. Significantly more
male fox terriers and basenjis formed dominance relationships than did
females, whereas beagles and cocker spaniels did not show gender-specific
differences in dominance relationships. Shelties (Shetland sheep dogs) devel-
oped strong territorial rather than food-related dominance relationships,
whereas basenjis showed the opposite pattern: absence of territorial aggres-
sion but escalated aggression over food ( Hahn and Wright, 1998; Scott and
Fuller, 1965 ).
Measuring emotional reactivity showed significant differences among the
breeds: terriers, beagles, and basenjis were consistently more emotional than
shelties and cockers. Although significant differences in breed reactivity
were observed, a variation in reactivity was also very apparent among indivi-
duals from the same breed. This reactivity showed very little change with
age and no differences between males and females.