Biomedical Engineering Reference
In-Depth Information
must show temporal and spatial unity to communicate, and
cooperation is a result of communication. Aggregations of
animals usually result from external factors, such as
a concentration of food, or from spatial constraints, such as
laboratory caging. A social group, on the other hand,
consists of individuals that prefer to associate with one
another. Understanding the differences between aggrega-
tions and social groups is important when managing captive
groups of nonhuman primates. Using the definitions out-
lined earlier, one can predict how groups of animals will
react to changes in their environment. When establishing
social groups in the laboratory, one must recognize the
social tendencies of a species. Once the group is estab-
lished, group and non-group animals are distinguished by
an increase in cooperative, directed aggressive behavior by
group animals toward new, non-group animals.
When studies involve captive animals living in groups,
much of this definition of what constitutes a social group
loses meaning. The animals necessarily communicate more
among themselves than with other groups because they are
restricted by the confines of their cages. However, these
patterns of communication between captive animals can be
used as the defining feature by which to study the rela-
tionships within a group (
Williams, 1983
). Using intra-
group interactions, it is possible to study subgrouping and
the various levels of nonhuman primate societies. These
studies emphasize the communication system within
a group and the measures of specific intragroup social
responses such as grooming, facial expression, and sexual
responses. These responses are usually distinct and are
easily quantifiable in terms of frequency or duration when
one is dealing with a small captive group. When studying
captive primates in large compounds, however, one might
need a great deal of time to determine social communica-
tion patterns using responses
Ecological Pressures on Nonhuman
Primate Social Structures
Several theorists have attempted to organize nonhuman
primate social structures into conceptual models relating to
various ecological contingencies (
Crook and Gartlan, 1966;
Fleagle, 1992; Isbell and Young, 2002; Kappeler and van
Schaik, 2002
).
Crook andGartlan (1966)
arranged the species
they studied into four levels of social organization: nocturnal,
diurnal
tree
savannah, and diurnal
e
omnivorous
e
arid savannah. Another
approach (
Denham, 1971
) considered the influence of
food density and distribution and predation. In that study,
each variable was dichotomized, and all possible combina-
tions of these variables were examined to predict sets of
conditions. Space and resource allocation, sex ratios, and
mating strategies were among the dependent variables. The
model in the Denham study has an advantage over that of
Crook and Gartlan in that the former specified some variables
associated with food as a resource and led to speculation on
how these variables might relate to energy acquisition by the
group.
Eisenberg et al. (1972)
attempted to relate phylogenetic
and ecological variables to one aspect of social structure:
the degree of male involvement in group interactions.
These authors postulated that adult males serve four roles in
social groups: maintaining spacing between closed groups;
reducing competition by forcing out younger males; pro-
tecting the group; and providing leadership by initiating
and maintaining movement of the group. These functions
were left to the males because the females were preoccu-
pied with protecting and socializing the infants.
frugivorous
forest,
diurnal
omnivorous
e
e
e
e
GENERAL STATEMENT ON NONHUMAN
PRIMATE SOCIAL STRUCTURES
It is difficult to make general statements about nonhuman
primate social structures (
Strier, 1994
), but most fit into one
of five broad categories: solitary, monogamous (and
possibly polyandrous), single-male/multi-female, multi-
male/multi-female,
like grooming,
facial
expressions, and sexual responses.
Analysis of the spatial arrangements of captive groups
should give a preliminary indication of a group's commu-
nication patterns and the lines along which this communi-
cation occurs. This type of cliqual analysis assumes that if the
animals are subgroups with a consistent pattern, some form
of communication was required to establish these partner
preferences. Animals in a nonsocial aggregation should
associate with each other in a random or nonsystematic
fashion, since no appreciable levels of organized communi-
cation, either agonistic or affiliative, are expected to occur
among them. Social groups, on the other hand, should show
more organized social responses. Since these responses are
affiliative or agonistic, the animals should develop partner
preferences, and their spatial distribution should reflect these
preferences. Any radical change in normal social interaction
patterns may presage an outbreak of aggressive behavior and
spontaneous social reorganization; these events will demand
time from the care staff to control.
fusion communities.
Kappeler and van Schaik (2002)
provide a good review of
the interrelation between social structure, social organiza-
tion, and mating systems. Below we provide a general
overview of how many nonhuman primate species fit
and
fission
e
e
some neatly and others not so neatly
into these five broad
e
categories of social structures.
Solitary Primates
Solitary primates include species that forage largely soli-
tarily and exhibit direct contact between the sexes infre-
quently. Solitary primates include the nocturnal primates
Lorisidae and Tarsiidae, whose habitats range from Africa
