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Vigilance and Mixed-Species Association of Some East African Forest Monkeys

Marina Cords
Behavioral Ecology and Sociobiology
Vol. 26, No. 4 (1990), pp. 297-300
Published by: Springer
Stable URL: http://www.jstor.org/stable/4600407
Page Count: 4
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Vigilance and Mixed-Species Association of Some East African Forest Monkeys
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Abstract

The frequency of looking up was scored as a measure of vigilance behavior in two species of African forest monkeys (genus Cercopithecus) that often associate in mixed-species groups. The fact that looking up decreased with increasing foliage density around focal individuals was taken as evidence that looking up is an expression of vigilance for predators. The rate of looking up was higher in single-species groups than in mixed species groups for both species. Association had a more marked effect on the rate of looking up when monkeys fed on plant material as opposed to insects. The adjustment of the rate of looking up with respect to association status does not reflect the presence or absence of other monkeys in the same feeding tree. Although a reduction in vigilance levels probably leads to increased feeding efficiency, it is not a sufficient explanation of mixed-species association in the species under study.

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