Behavioral Genetics and Animal Science - Genetics and the Behavior of Domestic Animals - page 20

show varying degrees of stress and stress hormone levels proportional to the
degree of novelty of the environment they are placed in. A glass jar is totally
novel in appearance compared to a lab cage the animal is accustomed to.
Being placed in a glass jar was more stressful for rats than a familiar lab
cage with no bedding.
Studies of reactions to novelty in farm animals have been conducted by
Moberg and Wood (1982) , Stephens and Toner (1975) , and Dantzer and
Mormede (1983) . Calves show the highest degrees of stress when placed
in an open-field test arena very dissimilar from their home pen ( Dantzer and
Mormede, 1983 ). Calves raised indoors were more stressed by an outdoor
arena and calves raised outdoors were more stressed by an indoor arena. The
second author is familiar with similar responses in horses. When horses are
taken to the mountains for the first time, a well-trained riding horse accus-
tomed to different show rings may panic when it sees a butterfly or hears a
twig snapping on a mountain trail.
Genetic Factors and the Need for Novelty
In mammals and birds, normal development of the brain and sense organs
requires novelty and varied sensory input. Nobel prize winning research
of Hubel and Wiesel (1970) showed that the visual system is permanently
damaged if kittens do not receive varied visual input during development. Dogs
are more excitable when raised in barren and non-stimulating environments
( Melzack and Burns, 1965; Walsh and Cummins, 1975 ). Schultz (1965) stated;
“when stimulus variation is restricted central regulation of threshold sensitivities
will function to lower sensory thresholds.” Krushinski (1960) studied the influ-
ence of isolated conditions of rearing on the development of passive defense
reactions (fearful aggression) in dogs and found that the expression of a well-
marked fear reaction depends on the genotype of the animal. In this experiment,
Airedales and German shepherds were reared under conditions of freedom
(in homes) and in isolation (in kennels). Krushinski (1960) found that the
passive defense reaction developed more acutely and reached a greater degree
in the German shepherds kept in isolation compared to the Airdales. In general,
animals reared in isolation become more sensitive to sensory stimulation
because the nervous system attempts to readjust for the previous lack of
stimulation.
In an experiment with chickens, Murphy (1977) found that chicks from a
flighty genetic line were more likely to become highly agitated when a novel
ball was placed in their pen, but were more attracted to a novel food than
birds from a calm line. Cooper and Zubeck (1958) and Henderson (1968)
found that rats bred to be dull greatly improved in maze learning when
housed in a cage with many different objects. However, enriched environ-
ments had little effect on the rats bred for high intelligence. Greenough and
Juraska (1979) found that rearing rats in an environment with many novel