PRIMATE SCIENCE RESEARCH HIGHLIGHT
April 8, 1999
"Muriqui monkeys are unique among social primate species"
(Courtesy Wisconsin Regional Primate Research Center)

Male muriqui monkeys live in highly social groups-multi-male and
multi-female. Yet they do not show elevated levels of testosterone during
the breeding season as do males of other social nonhuman primate species, a
recently completed 19-month field study in Brazil has revealed.

These findings, by Drs. Toni Ziegler and Karen Strier of the University of
Wisconsin-Madison, substantiate that testosterone surges among the males of
nonhuman primate species living in highly social groups may not always be
related directly to the onset of breeding, but rather to the increased
competition for females.

The seldom studied endangered muriqui-the researchers studied six males at
a field site in Minas Gerais, Brazil--is by nature a nonaggressive species.
Unlike most monkeys, its social structure shows no overt evidence of being
based on a dominance hierarchy. Yet, Ziegler and Strier still believed
these animals might show testosterone surges during the breeding season
just as do male rhesus, mouse lemur, squirrel and many other monkeys.

When analysis of the males' feces collected during the fall breeding season
revealed no upswings in testosterone when compared with samples taken
during the rest of year, the researchers knew they had revealed a novel
characteristic of this elusive species. This basic biological finding is
even more remarkable when one considers that the researchers did not even
have to touch the animals or disrupt the colony in any way during the
entire study period.

The muriqui research may lead to further studies on how basic temperament
affects testosterone levels, aggression and breeding in other primate
species.

The fecal steroid assay techniques developed at the Wisconsin Regional
Primate Research Center and used for this study also show promise for
helping researchers learn more about the breeding and behavior of other
endangered monkeys. Conservationists who have a better understanding of the
populations they are trying to preserve can develop new ways to promote the
protection and perpetuation of these populations, both in captivity and in
the wild. This work is critical as habitats and populations continue to
shrink for many nonhuman primate populations.

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Reference:

Strier, K.B., T.E. Ziegler, and D. Wittwer. 1998. Seasonal and social
correlates of fecal testosterone and cortisol levels in wild male muriquis
(Brachyteles arachnoides). Hormones and Behavior (in press).


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Primate-Science Research Highlights appears every other week and focuses
broadly on research involving non-human primates. Coverage includes
biomedicine, behavior, conservation and veterinary science. Please
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supported by a grant from the National Institutes of Health,
National Center for Research Resources.  Copyright 1999,
Wisconsin Regional Primate Research Center. No portion of this highlight
may be copied or redistributed without the consent of the editor.

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