Biomedical Engineering Reference
In-Depth Information
although progress has been made in identifying potential
risk factors for the development of pathological behaviors,
the etiology of behavioral pathology in individual
nonhuman primates remains largely unclear. As a result,
animals are identified in the colony after they develop
pathological behavior, and only retrospective, correlational
analyses are available to identify possible risk factors and
determine effective treatments. Second, deviant behavior is
a symptom and not necessarily a disorder per se. Thus, in
some cases, abnormal behavior may either be a conse-
quence of a medical condition (e.g. arthritis) or psycho-
logical disorder (e.g. anxiety). In yet other cases, abnormal
behavior may reflect a coping strategy to increase stimu-
lation or to decrease arousal. In light of the issues
surrounding the etiology of behavioral pathologies, we
shall consider the treatment of abnormal behavior in three
broad categories, social interventions, environmental
interventions, and pharmacological therapies.
previously housed in individual cages as adolescents or
adults might yield similar benefits (e.g. an increase in
species-typical behavior and a reduction in abnormal
behavior). Indeed, research focused on animals that had
a prior history of individual cage housing and were then
socially housed provides some support for this view.
Several studies emphasize the physiological and behavioral
benefits to pair and group housing as an intervention
strategy. Pair housing typically results in increased species-
typical behavior and can also lead to decreased heart rate
and increased affiliation (
Doyle et al., 2008
). In some cases,
pair housing is associated with reductions in abnormal
behavior. For example, pair housing reduced abnormal
behavior in female rhesus monkeys (
Eaton et al., 1994
), and
decreases in whole-body and self-directed stereotypies
were similarly observed in male baboons housed in pairs or
groups of three (
Bourgeois and Brent, 2005
). Social
housing has also been associated with a decline in stereo-
typic behavior (
Schapiro, 2002
) and with a reduced inci-
dence of SIB in some animals (
Reinhardt and Rossell,
2001; Weed et al., 2003
). However, there may be limita-
tions to this approach, as
Doyle et al. (2008)
found only
temporary reductions in abnormal behavior in paired male
rhesus monkeys.
Concerns about incompatibility and impact on research
are often raised with respect to moving animals from single
cage to pair or group housing. In terms of compatibility,
much is known about appropriate means of establishing
compatible pairs of nonhuman primates. Pairing of
monkeys of different age and sex classes has been
successfully performed with no negative effects on the
body weight or behavior of the animals (
Reinhardt, 1988;
Reinhardt et al., 1988a, 1988b
). Additionally, compatible
pairs of rhesus monkeys equipped with implantable devices
have been established with no resulting damage to the
experimental equipment (
Roberts and Platt, 2005
),
a common experimental concern of housing research
monkeys with each other. However, it should be recognized
that not all animal pairings will be successful, particularly
when one or both animals are extremely aggressive.
Social Interventions
Because abnormal behavior is strongly linked with indi-
vidual housing, much attention has been focused on social
therapies, i.e. pairing or group housing monkeys after
a period of time in individual cage housing. Interest in
social therapies began in the 1970s as a result of the pio-
neering work of Harlow and colleagues in rehabilitating
monkeys reared in isolation as infants. Isolation-reared
monkeys developed such severe deficits that they were
considered the most difficult case for rehabilitation.
Although these animals showed some recovery of social
function and reduction in abnormal behavior with social
exposure, the most important message of this research was
that the kinds of partners determined the outcome. Pairing
isolates with normally reared age-mates was not thera-
peutic because of aggression directed by normally reared
monkeys to the isolates (
Capitanio, 1984; Mason, 1960,
1961b; Cross and Harlow, 1965; Mitchell, 1970
). Although
isolation-reared monkeys could be paired with one another
without producing heightened aggression, no significant
benefit in terms of a reduction in abnormal behavior or an
increase in social behavior was derived from such contact
(
Suomi, 1973
). In contrast, exposure of 6- or 12 month-old
isolation-reared monkeys to less socially sophisticated
partners of 3
Human Interaction and Positive
Reinforcement Training
Increased human interaction is presented as a possible
strategy for enriching the environment of nonhuman
primates in the Animal Welfare Act when they suggest
“providing interaction with the care giver or other familiar
and knowledgeable person consistent with personnel safety
precautions” (Animal Welfare Act, 1991). Human inter-
action can take the form of social behavior in which
humans interact with monkeys using species-typical signals
or providing treats, or it can focus on behavioral change in
4 months of age resulted in substantial
changes in behavior (
Suomi and Harlow, 1972; Novak and
Harlow, 1975
). The isolation-reared monkeys exhibited
a marked decline in abnormal behavior and showed a cor-
responding increase in social contact, exploration, and play,
although improvement was not observed in all forms of
social behavior (
Suomi and Harlow, 1972; Novak and
Harlow, 1975; Novak, 1979
).
Although animals are not reared in isolation today, it is
reasonable to assume that pairing monkeys that were
e
