Biomedical Engineering Reference
In-Depth Information
structures of these foraging groups vary, but the most
common structure consists of a female and offspring with
an adult male (
Norconk and Kinzey, 1994
). Chimpanzee
communities can range from 30 or fewer animals to over
100. Subgroups can range in size from one to the total
group, with subgroups of one to six being the most
common. Male chimpanzees may be more social than are
females, who spend more time alone or with only their
offspring.
Variations of the fission
vertebrates, and fruits. Marmosets also have several adap-
tations that allow them to digest gums (
Harrison and Tardif,
1994; Power and Oftedal, 1996
). Over 80% of marmoset
births are twins. Wild populations of callitrichids are
usually seen in groups of 2 to 10 animals that are assumed
to comprise a breeding pair and several sets of offspring
that serve the group by helping to carry the infants.
However, recent field data have shown a high degree of
variability in the callitrichid mating system (
Sussman and
Garber, 1987; Ferrari and Lopes Ferrari, 1989
), with about
61% of wild social groups containing only one breeding
female and multiple adult breeding males that help rear the
infants. This observation suggests that callitrichids have
much flexibility in their social structures and that different
species within this group may be very adaptable.
fusion structure have been
seen among hamadryas baboons (P. hamadryas)(
Kummer,
1968; Sigg et al., 1982
) and gelada baboons
(Theropithecus)(
Kawai et al., 1983
). These species are
typically referred to as single-male breeding units;
however, these units seem to coalesce into larger social
groups that travel or sleep together. The mechanism for
maintaining the breeding units is entirely different between
the two species. Hamadryas baboon males actively herd
females and retrieve those that stray too far. The males
begin this behavior as adolescents by kidnapping a young
female and actively training her. The primary bond is
between the male and each female. On the other hand,
gelada females are the cohesive force behind their breeding
units. These females bond to each other, and the male then
joins the females but does not herd them.
Large gatherings of gelada single-male units may be
social aggregations, with little interaction between the units
other than among female relatives. Hamadryas, however,
have distinct levels of social organization above the single-
male unit. Several units may constitute a clan that moves
together over a long period of time. Clans consist of several
related or familiar males. Several clans come together to
form a band, and sleeping troops consist of several bands.
Since troops primarily come together at scarce sleeping
sites, the ability to mingle with other bands at the closest
site each day is an advantage. In contrast, geladas divide
into single-male units to sleep at night and form large
aggregations to feed during the day.
e
Saimiri
Cebus
Squirrel monkeys and Cebus live in multi-male/multi-
female social groups. Average group sizes for both Cebus
and Saimiri range between 10 and 30 animals (
Baldwin,
1971; Baldwin and Baldwin, 1981; Terborgh, 1983
).
Squirrel monkeys are polygamous and show high male
aggressive behavior during the breeding season. Some
subspecies show sexual segregation during the nonbreeding
season (
Coe and Rosenblum, 1974
). Most affiliative
behavior is seen between females and consists of moving
together and sitting huddled together
and
(
Baldwin and
Baldwin, 1981
).
Some Cebus maintain age-graded male structures with
one dominant male usually the only one who mates. In
Cebus olivaceus, the dominant female is usually the most
aggressive animal (
Robinson, 1981
). Dominance rankings
are linear, and rank reversal is rare (
Izawa, 1980
). Domi-
nance status affects the spatial organization within Cebus
paella groups (
Janson, 1990
). The feeding position of an
individual is related to the amount of aggressive behavior it
receives from the dominant male. Cebus capucinus,
however, is a dispersed feeder and exhibits scramble
competition so that dominance has less influence on
feeding (
Phillips, 1995
).
Grooming is very important and is usually directed
toward the dominant male or female (
Robinson and Janson,
1987
). Dominant animals may well interact twice as much
as lower-ranking animals do. Both males and females
emigrate from natal groups; however, the mechanism
behind these transfers is not well understood.
Alloparenting plays an important part in the socializa-
tion of both squirrel monkeys and Cebus. Squirrel monkey
infants may spend up to 30% of their time with an allo-
mother (
Baldwin and Baldwin, 1981; Williams et al.,
1994a
). Allomothers tend to be young adult animals or
females that lost infants earlier in the year. Some infants
spend more time with allomothers than with their actual
Typical Laboratory Species
Six genera of primates are currently most prominent in
research laboratories: Callitrichidae, Cebus, Saimiri,
Macaca, Papio, and Pan.
Callitrichidae
Callitrichidae can be separated from other New World
monkeys on the basis of several characteristics. Marmosets
and tamarins have three premolars (like all cebids) but only
two molars, claws for climbing, and diets that are more akin
to the diets of prosimians than to those of most other
anthropoids. Both tamarins and marmosets are diurnal
arboreal quadrupeds
that
tend to eat
insects,
small
