Biomedical Engineering Reference
In-Depth Information
procedure by modern investigators, it is nonetheless
sometimes used as a “default” husbandry procedure under
certain circumstances (e.g. occasional maternal rejection
necessitating nursery rearing even though there are no other
animals in the nursery at that time). It is therefore important
for colony managers to understand the consequences, both
short- and long-term, of isolation rearing.
Monkeys reared in small isolation chambers or in mesh
cages without physical contact for the first 6
self-biting) and failed to modify these behavior patterns
with age or experience. Females, on the other hand,
appeared to be somewhat buffered from the effects of total
isolation rearing and modified their responses with expe-
rience (e.g. some improvement in maternal behavior
occurred with the birth of a female's second infant;
Arling
and Harlow, 1967; Sackett, 1974
).
Many of the behavioral abnormalities that define the
isolation syndrome (e.g. self-directed activity and inade-
quate social behavior) for rhesus macaques were also
observed in chimpanzees (
Davenport and Menzel, 1963;
Rogers and Davenport, 1969, Turner et al., 1969
) and
squirrel monkeys (
Roy, 1981
) following isolation rearing.
In contrast to rhesus monkeys, isolation-reared chimpan-
zees acquired appropriate copulatory postures upon expo-
sure to sexually competent chimpanzees (
Turner et al.,
1969
). Unexpectedly, macaque species were shown to
differ in their vulnerability to isolation rearing (
Sackett
et al., 1976
). In a comparative study of the effects of
isolation on three species of macaques (rhesus, pigtail, and
cynomolgus), rhesus and cynomolgus macaques showed
significantly higher levels of abnormal behavior than
pigtail macaques, suggesting that effect of isolation rearing
on abnormal behavior was species-dependent.
The devastating effects of isolation rearing on infant
development in several nonhuman primate species empha-
size the need for caution in rearing infants without physical
contact with conspecifics. Animals reared in this manner
have severely compromised welfare, display high levels of
abnormal behavior, are difficult to socialize even under the
best of circumstances, cannot be used for breeding, and
make poor research subjects.
12 months of
life developed profound behavioral and physiological
abnormalities referred to as the isolation syndrome (see
Capitanio, 1986; Harlow and Harlow, 1962, 1965; Sackett,
1965, 1968; Mitchell, 1968, 1970
for reviews). The
symptoms of the isolation syndrome included: (1) failure to
develop positive social relationships; (2) inadequate
development of facial expressions and complex motor
responses (e.g. double foot clasp mount essential for
reproduction); (3) emotional disturbances such as height-
ened fear or aggression; and (4) bizarre postures and
stereotypic behaviors (
Mason, 1968
). These abnormalities
persisted throughout
e
the
lifetime of
the
individual
(
Mitchell, 1968
).
Isolation-reared infants showed behavioral disturbances
that included rocking, huddling, self-clasping, and exces-
sive self-orality that emerged within the first 2 months of
life (
Cross and Harlow, 1965; Harlow and Harlow, 1965
).
At 6 months of age, most of the isolated monkeys exhibited
multiple kinds of stereotypic behavior that included both
motor stereotypies and self-directed stereotypies, with the
three most common patterns being rocking, huddling, and
self-clasping. The incidence of self-clasping and digit
sucking decreased over time, whereas other kinds of
stereotypies increased such as somersaults, head bobs,
unusual limb manipulations (e.g. leg behind neck, floating
limb), and in some cases, SIB (
Fittinghoff et al., 1974;
Mitchell et al., 1966; Mitchell, 1968; Sackett, 1968
).
Isolation-reared monkeys additionally failed to develop
even the most basic social skills. When exposed to normal
infants of the same age, isolates reacted with excessive fear
(
Mason and Green, 1962
) and failed to show appropriate
species-typical social behavior (
Sackett, 1968
). As juve-
niles, isolation-reared monkeys showed unstable domi-
nance interactions with frequent and prolonged fighting
(
Mason, 1961b
). As adults, such monkeys were hyperag-
gressive in social situations and did not develop positive
social relationships with other monkeys (
Anderson and
Mason, 1974; Mason, 1961a
). Reproductive behavior was
also abnormal in that males never acquired the appropriate
sexual mounting posture (
Mason, 1960
) and artificially
inseminated females were indifferent or abusive to their
first-born infants (especially male infants, cf.
Suomi, 1978
).
As a general rule, males appeared to be more vulnerable
to the effects of isolation than females. Males were more
likely to exhibit grossly abnormal behavior (e.g. excessive
Nursery Rearing
In the nursery rearing condition, Harlow and associates
examined the effect of separating infants from their mothers
at birth and rearing them with other infants of approxi-
mately the same age. Two different rearing procedures were
examined: (1) peer-only rearing wherein infants were
continuously reared with infants of approximately the same
age, and (2) surrogate-peer rearing wherein infants were
continuously housed with an inanimate surrogate mother
and given brief daily exposure (15 min to 2 hours) to other
infants of approximately the same age in a playroom
setting.
Understanding the effects of nursery rearing continues to
be important today, particularly in light of the number of
primates being imported to the USA for research purposes
from breeding colonies around the world. Many primate
facilities maintain breeding colonies and must be prepared to
rear infants in a nursery setting in situations when research
protocols require it, when maternal behavior is disrupted
due to illness or failure to lactate or is inappropriate
