Behavioral Genetics and Animal Science - Genetics and the Behavior of Domestic Animals - page 17

observed in cattle. Cattle curiously approach a novel clipboard laid on the
ground, but when the wind flaps the paper, they fearfully jump back. When
the paper stops moving, the cattle approach it again. The nucleus accumbens
may be in SEEK mode when cattle voluntarily approach and switches into
fear mode when the paper suddenly moves.
Genetics and Emotional Systems
Research clearly shows that genetic factors have a very strong effect on both
fearfulness and novelty seeking ( Campler et al., 2008 ; Clinton et al., 2007 ;
Stead et al., 2006; Yukihide et al., 2005). Maternal factors had little effect on
novelty seeking in rats (Stead et al., 2005). Cross-fostering also had little
effect, which shows that novelty seeking is highly heritable. Animals that are
high seekers have more dopaminergic activity in the nucleus accumbens ( Dellu
et al., 1996 ). In addition to the heritable component to fearfulness, environ-
mental influences also have an effect on fearfulness. Stressful treatment of
either a pregnant mother or her offspring can upregulate the fear system.
Lemos et al. (2012) propose that severe stress can disable the appetitive system
in the nucleus accumbens. To state it more simply, stress can break the ani-
mal's SEEK function and it will no longer explore. Other emotional systems
are also subject to both genetic and environmental influences. The PANIC
(separation distress) system is highly heritable. In sheep, separation distress
measured by isolating a single animal and measuring how many times it bleats
(vocalizes) shows that vocalization is highly heritable ( Boissy et al., 2005 ).
Strength of the sex drive is also heritable. When the first Chinese pig breeds
were imported into the U.S., caretakers observed that boars were more highly
motivated to mate compared to U.S. and European commercial pigs. The
Chinese pig was bred for large litter size and low levels of meat production.
INTERACTIONS BETWEEN GENETICS AND EXPERIENCE
Some behavior patterns are similar between different species, and some are
found only in a particular species. For example, the neural programs that
enable animals to walk are similar in most mammals ( Melton, 1991; Grillner,
2011 ). On the other hand, courtship rituals in birds are very species-specific
( Nottebohm, 1977 ). Some innate behavior patterns are very rigid and experi-
ence has little effect on them. Other instinctive behaviors can be modified by
learning and experience. The flehmann, or lip curl response of a bull when he
smells a cow in estrus, and the kneel-down (lordois) posture of a rat in estrus
are examples of rigid behaviors. Suckling by newborn mammals is another
example of a hard-wired behavioral system. Suckling behavior does not vary.
Newborn mammals suckle almost everything put in their mouth.
An example of an innate behavior affected by learning is burrowing
behavior in rats. Boice (1977) found that wild Norway rats and albino