Genetics and Behavior During Handling, Restraint, and Herding - Genetics and the Behavior of Domestic Animals - page 116

Herding animals orient and point both their eyes and ears in the direction
of any novel sight or sound. Orienting responses alert the animal to possible
danger, are accompanied by an internal state of nervous system arousal
( Boissy, 1995; Davis, 1992; Rogan and LeDoux, 1996 ), and elicit responses
modulated by the nucleus accumbens in the brain. The nucleus accumbens
mediates both fearful (FEAR) motivation toward threats and appetitive
(SEEKING) motivation for rewards ( Faure et al., 2008 ; Reynolds and
Berridge, 2008 ). When an animal orients towards a novel stimulus, it may
freeze, stand completely still and watch (SEEKING) mode, or go into
(FEAR) motivated anti-predator mode. The authors speculate that during the
orienting response when animals are watching, the nucleus accumbens
remains in SEEKING mode. The nucleus accumbens in the brain acts as a
biochemical switch and contains neural circuits that can turn on fearful beha-
viors or approach-seeking behaviors. Typical fear-motivated behaviors are
fleeing, bunching closely together, or fighting when the animal is trapped or
defending calves. Both genetic factors and experience affect the response in
the nucleus accumbens to either fearful stimuli or the motivation for rewards.
For instance, rodents subjected to loud rock music and bright lights were
more fearful because the fear-generating zones in the nucleus accumbens
have expanded ( Reynolds and Berridge, 2008 ). Conversely, a preferred home
environment (familiar, dark, quiet) caused appetitive-generating zones to
expand.
Differences in the Strength of Herding Behavior
of Cattle and Sheep
The first author has observed that wild ungulates such as the American bison
have stronger herding behavior compared to domestic cattle. Separation of a
single animal from the herd will cause it to make an intense effort to rejoin
its herdmates ( Grandin, 1993 ). Possibly this behavior is driven by the emo-
tion of PANIC (separation distress). Domestic cattle become more difficult
to handle and sort when they become agitated and engage in bunching, or
milling. Each animal will attempt to push itself into the middle of the group
where it will be safe from predators. The strongest animals end up in the
middle of the milling herd. In their natural environments, prey species ani-
mals such as elk and deer spread apart when grazing a hillside, but at the
first sign of danger group closer together and flee as a herd. Domestic cattle
living in areas with a large number of predators, such as wolves, graze in
tighter groups than cattle reared in areas free of predators (Joe Stookey, per-
sonal communication, 2012). Small domestic herding animals such as sheep
display similar behavior. When herding animals sense danger, they tend to
flock together. Sheep tend to be more reactive and herd together more tightly
compared to cattle. Sheep are more vulnerable to predators than cattle, there-
fore bunch together very tightly to find safety in numbers. Bunching is the