Group-housing (photos 12-14)
provides compatible companionship
for the expression of non-injurious social behavior
Photos 12 & 13: Housing nonhuman primates in groups would
be the ideal way of social enhancement (photo 12), but there
can be serious problems associated with it.
Overt aggressive conflicts are rather common in groups kept in
research laboratories (photo 13). Referring to rhesus macaques,
Rolland  makes the following observation: "By far
the most common physical problem that I treat as a clinical veterinarian
is trauma sustained by macaques in group-housing situations.
This occurs even when no changes have been made within a previously
compatible group [e.g., Reinhardt et al., 1987a; Judge et al.,
1994]. The incidence of traumatic injuries is increased when
new groups are formed [e.g., Bernstein & Gordon, 1977; Line
et al., 1990a; Reinhardt, 1991a; Clarke & Blanchard, 1994;
Westergaard et al., 1999] or when animals have to be removed
and reintroduced into a group [e.g., Southwick, 1967; Bernstein
et al., 1974] for medical reasons, as inevitably occurs. Trauma
may range from superficial abrasions to multiple wounds and lacerations,
sometimes leading to life-threatening loss of blood and shock."
During an eight-month period, "there were 57 injuries requiring
removal from group housing and treatment in the clinic in our
group-housed, timed mating colony of about 120 females."
Mortality caused by fighting may occur at a rate of 10 or even
more deaths per 100 group members per year [Kaplan et al., 1980;
Kessler et al., 1985].
Photo 14: Are rhesus macaques really so
Probably not, because the species thrives in groups under
natural living conditions [Southwick et al., 1965; Lindberg,
It is us who create the problem, by forcing the animals
to live in a confined, inadequately structured environment which
is bound to provoke conflicts. Moreover, personnel often is lacking
the time, the administrative authority - to guarantee optimal
group stability - and the knowledge to manage group-housed animals
in accordance with ethological principles.