Behavior Genetics of the Horse (Equus caballus) - Genetics and the Behavior of Domestic Animals - page 267

Holstein cattle reported by Broucek et al. (2007) . (Holstein cattle are also
known for their calm and gentle nature.) Gorecka-Bruzda et al. (2007) also
found that hair whorl position in Konik horses is highly heritable. The esti-
mates are similar to the heritability estimates of hair whorls in Holstein cattle
( Shirley et al., 2006 ). It would be interesting to repeat the study of Gorecka-
Bruzda et al. (2006) using breeds known to have highly reactive tempera-
ments, such as Thoroughbreds or Arabians. It is clear that cattle producers,
horse breeders, horse trainers, and horse owners could benefit from further
studies of hair whorl position and rotation and its relationship to tempera-
ment. The evidence presented supports much of the anecdotal evidence col-
lected by the first author. Further evidence of a relationship between hair
whorls and side preference is presented in the next section.
LATERALIZATION IN THE NERVOUS SYSTEM
Humans and animals have two types of laterality. One is motor laterality, the
other is sensory laterality. The most common examples of motor laterality
are right- and left-handedness in humans and side or limb preference in ani-
mals. Humans throw a ball or write better with either the right or left hand.
Animals prefer to start walking using either the right or left foot, or the right
or left paw to hold or manipulate objects. Sensory laterality refers to special-
ized tasks of both brain hemispheres. In most humans, the left hemisphere
controls language, and the right hemisphere has strong control of emotions.
Although specialized functions of brain hemispheres were long considered
unique to humans, increasing evidence points to behavioral asymmetry as a
fundamental principle of organization in vertebrate behavior ( Vallortigara
and Rogers, 2005 ; McGreevy et al., 2007 ). At the most basic level, both
sides of vertebrate brains show strong and consistent behavior patterns. In
animals as diverse as chickens, fish, lizards, rodents, and humans, most
approach behaviors (finding food and friends) are left hemisphere tasks, and
most avoidance behaviors (responses to predators and novel stimuli) are right
hemisphere tasks. According to Rogers (2010) , complimentary hemispheric
specialization occurred during the course of evolution so that animals could
search for food and remain vigilant for predators at the same time. Generally
the left hemisphere categorizes information and controls routine behavior,
whereas the right hemisphere is responsible for responding to novel events,
and coordinating rapid responses. Stressed or frightened animals rely on pre-
dominant use of the right hemisphere ( Rogers, 2010 ). Genes and environ-
ment influence lateralization, but the interaction between them is not always
clear ( Schaafsma et al., 2009 ).
LATERALITY IN HORSES
Horses show a preference to stand with one foot forward while grazing, to
use either the right or left foreleg to initiate a walk or a trot, to roll on their