Biomedical Engineering Reference
In-Depth Information
mothers during their first month, and infant swapping has
been verified genetically in the laboratory setting ( Williams
et al., 1994b ). Although no allopaternal behavior has been
reported in Saimiri, C. apella mothers regularly leave their
infants with the dominant male ( Robinson and Janson,
1987 ).
Male
male interactions are generally more aggressive than
affiliative. The greeting response between males is char-
acterized by stereotypical vocalization, facial expressions,
ritual mounting, and touches. While competitive factors do
influence a male's access to females, other factors, such as
tenure in the group, alliances, and female choice, also can
determine mating partners ( Silk et al., 2003; Weingrill
et al., 2003 ). Alternative mating strategies among males
mean that the correlation between male dominance rank
and paternity is far from perfect.
e
Macaca
All macaque species show the same basic social structure:
multi-male/multi-female groups with a sex ratio skewed
toward the females. The groups typically move as an
integrated unit and do not regularly split up into subgroups.
Females do not typically emigrate and instead form the
core social nucleus of the groups. Close bonds are main-
tained within the matriarchies. Stable, linear dominance
hierarchies among the females are the norm. Among the
macaques, rank is typically passed on to the daughters in an
inverse fashion so that the youngest daughters tend to rank
higher than their older siblings ( Berman, 1980 ). Males
compete against other males within the group. Most inter-
actions between males are aggressive and dominance
oriented. Even when they are cooperating in aggressive
behavior against a third male, there is little positive inter-
action other than running beside each other or mounting.
Male
Pan
Chimpanzee communities contain from 20 to 100 individ-
uals of all ages and both sexes ( Hiraiwa-Hasegawa et al.,
1984 ). Within these communities, chimpanzees associate
as parties or bands. These subgroups can last up to several
days and vary in size from one to more than 60 individuals,
although parties of six or fewer account for over 80% ( van
Lawick-Goodall, 1968 ). Although any combination of ages
and sexes may make up these parties, mother
offspring
e
pairs are the only stable parties. The mother
infant rela-
tionship lasts for several years beyond weaning, and older
males commonly travel with their mothers. Older females
and their mothers travel together much less. Unrelated
females interact only infrequently.
Adult male chimpanzees are consistently more sociable
than are adult females. Unrelated males and females do not
appear to form long-term relationships. Consortships, with
extensive interactions, may last for a day or a week. Female
chimpanzees transfer from community to community, and
data suggest that they usually migrate before giving birth
for the first time, during a period of estrus ( Nishida, 1979 ).
Once they have given birth, they tend not to transfer again.
Bonobos also live in community-style social organiza-
tions; however, parties of mixed ages and sexes predomi-
nate ( Nishida and Hiraiwa-Hasegawa, 1987 ). Over 90% of
the bonobo subgroups consist of mixed sex parties
compared with about a third of chimpanzee parties.
Bonobos typically form one of four types of groups:
matrifocal parties, male bands, male singletons, and female
singletons. Matrifocal parties comprise mothers and
offspring, including adult males, and are relatively stable.
Male bands consist of adult males of unknown relation.
Male singletons are usually old and/or disabled, whereas
female singletons are nulliparous females who are
presumed to be immigrants. Aggregations of matrifocal
units form the usual bases for a party. Matrifocal units may
also band together with a male band. Uehara (1988)
reported that at least two communities used the same
habitat without intermingling.
Like chimpanzees, bonobos have a linear male domi-
nance hierarchy. Food sharing and grooming occur
frequently between the sexes and between females but not
e
male grooming does occur but at a very low rate,
mostly during the nonbreeding season.
e
Papio
Savannah baboons live in multi-male/multi-female social
groups very different from the one-male units described
earlier for Papio hamadryas. Savannah baboons comprise
several species that live throughout the African savannah
region, including P. cynocephalus (yellow baboon),
P. ursinus (chacma baboon), P. anubis (olive baboon), and
P. papio (western or guinea baboon). Savannah baboons
have been called generalized feeders, eating everything
from grasses and flowers to insects and small mammals.
Groups of savannah baboons range from 20 to 100
individuals with a female-to-male ratio skewed toward
more females in the group. In most species, each social
group typically moves together as an integrated group and
does not regularly split into different subgroups. Females,
who usually remain in their natal group for their entire
lives, form the stable social core of the group and usually
have a fairly stable linear-style dominance hierarchy
( Altmann et al., 1977 ).
Each of these social groups contains more than one
male, and competition for access to estrous females occurs
within the group. Males typically transfer to different
groups around the age of puberty. Although the proximal
causes of male transfer are not clearly understood, the
immediate result is that the males within a group are less
related to one another than females are to each other.
Search WWH ::




Custom Search