Biomedical Engineering Reference
In-Depth Information
species of NHPs, marmosets and tamarins live in cooper-
ative breeding groups with a single breeding pair. In
captivity, these primates are often kept in groups consisting
of a breeding male and female and their subadult, juvenile
and infant offspring ( National Research Council, 1998 ).
Macaques and chimpanzees as well as other primate
species live in relatively large troops, and thus, living in
large outdoor enclosures is often considered the best type of
housing for them. Not only does living in a group provide
for the most complex social environment, but it also
provides exercise and cognitive stimulation. However,
group housing is not a viable option in all cases. The
constraints of the facility and the “function” (i.e. assign-
ment) of the animals are two factors that influence housing
options. Some research procedures are more readily
accomplished by housing NHPs in smaller cages rather
than in a group setting. However, advances in technology
and in animal training techniques are making it more
practical to group house NHPs even when they are involved
in a variety of biomedical research projects. For example,
implanting microchips as individual identifiers to be read
by computers has allowed studies of cognition in group-
housed macaques ( Fagot and Bonte, 2010 ) as well as
studies of biological factors affecting eating and obesity
( Arce et al., 2010 ). Training NHPs to cooperate with
common research procedures such as leaving their group
briefly for blood withdrawal ( Blank et al., 1983 ) or vaginal
swabbing for monitoring menses ( Jensen et al., 2010 ) also
allows the animals to benefit from living in social groups
while contributing to biomedical science. As training
becomes a more pervasive element of behavioral manage-
ment programs, there will be more opportunities like this in
the future, which will contribute to the well-being of
laboratory NHPs.
Caging should be selected to provide flexibility in the
degree and type of tactile and visual contact available to the
animals (see Chapter 9). Pair housing (i.e. housing two
monkeys in an appropriately sized cage) allows tactile
social contact between the partners and is a common type
of social housing for NHPs living indoors in the USA
( Baker et al., 2007 ). When full contact pair housing is not
appropriate (e.g. for certain approved research protocols or
for male
FIGURE 6.1 Subadult (foreground) and adult (background) male
pigtailed macaques ( Macaca nemestrina ) in Washington National
Primate Research Center-style grooming-contact cages. (Photo by
Carolyn M. Crockett.)
considered socially housed, they should be in tactile contact
to allow for touch and grooming. Therefore, as long as the
bars or holes on the grooming panel are wide enough to
allow the partners to put their hands through to groom one
another, this kind of housing should be considered “social,”
although it should not be preferred when full contact
pairing can be achieved.
Assessments of the behavioral benefits of grooming-
contact caging have found mixed results. Lee and
colleagues (in press) found few behavioral differences
between female longtailed macaque pairs when they were
housed in full contact versus when housed in grooming-
contact cages. In contrast, Baker and colleagues ( Baker
et al., 2008 ) found that abnormal behaviors of rhesus
macaques occurred at higher levels when the animals were
housed in protected-contact cages versus full-contact pair
housing. Although the empirical data are mixed, grooming-
contact cages do provide opportunities for certain types of
social contact, including grooming, a behavior that could
not happen in singly housed animals ( Crockett et al., 1997 ).
Social housing is not a universally accepted behavioral
management panacea for NHPs, however. Social housing
can result in serious injury if individuals are not compatible
and if information concerning natural species-typical social
groupings is not applied. Factors such as sex and age may
affect how well individuals get along with each other.
Given the xenophobic nature of some primate species,
forming compatible pairs or groups can be challenging. For
these species, keeping social units relatively stable can help
reduce aggression. When animals do need to be removed
from the social group (e.g. for trauma or illness), it is
important to return them to the group as quickly as possible.
female pairs), grooming contact panels ( Crockett
et al., 1997 ) between adjacent cages can be used in some
cases ( Figure 6.1 ). These panels are designed such that part
of the panel consists of widely spaced bars or holes that are
of sufficient diameter to permit the monkeys on opposite
sides of the panel to groom one another. Grooming contact
panels afford individual monkeys privacy as well as choice
in whether to engage in tactile social contact, including
grooming with the neighboring monkey ( Crockett et al.,
1997 ). Interestingly, while the Guide calls for social
housing of caged animals, what constitutes “pair housing”
is not clearly defined. For two or more caged NHPs to be
e
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