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Philopatry, male presence and grooming reciprocation among female primates: a comparative perspective 总被引:3,自引:0,他引:3
Competition for food and a safe location in a group are considered to be the main determinants of variation in social relationships
among female primates. The effect of the presence of males is usually overlooked, however. Here we put forward two hypotheses
connecting the (relative) number of males in a group, a statistic measuring the strength of positive relationships among females
(the degree of reciprocity of grooming) and female residence. Under the first hypothesis, we assumed that philopatric females
suffer especially from competition for males. Because females of these species are restrained to their native group and thus
do not move to groups where better conditions (i.e. more males) prevail, a higher socionomic sex ratio would imply reduced
competition and this should be reflected in better relationships among females (i.e. in a higher degree of reciprocation).
The second hypothesis is based on the contention of Wrangham (1987) that groups with more males are better able to defend
large food sources: in these groups female relationships would suffer less from within-group competition for food. We therefore
also expected a positive correlation between the absolute number of males and grooming reciprocation. To test the hypotheses,
matrices of grooming interactions were collected by going through the primatological literature. For ten female-resident and
four female-transfer primate species, the degree of grooming reciprocation was quantified using a specially adapted matrix
statistic. The results favoured the first (competition for males) hypothesis. The degree of grooming reciprocation among females
was positively correlated with socionomic sex ratio, but neither with group size nor with the absolute number of males. Correlations
between the degree of reciprocity and sex ratio were confirmed at three levels: within the same group at different points
in time, between groups of the same species, and between species. In addition, the degree of reciprocation increased with
sex ratio more strongly in typical single/variable male than in multi-male species. This we interpreted as a direct consequence
of the lower social availability of males for females in multi-male groups than single-male groups. In turn, this effect may
be due to males competing for females in multi-male groups.
Received: 28 May 1997 / Accepted after revision: 9 November 1997 相似文献
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