International Journal of Primatology, Vol. 11, No. 1, 1990 New World Primates, New Frontiers1: Insights from the Woolly Spider Monkey, or Muriqui (Brachyteles arachnoides) Karen B. Strier 2 Received July 6, 1988; revisedMarch 3, 1989 Despite over 25 years of intensive research, much of our knowledge of pri- mate behavior has been limited to a small number of Old World, semi- terrestrial species. With the exception of chimpanzees, these species share consistent patterns of behavior, including aggressive competition between males, male dominance over females, male dispersal and female kin groups, that have come to characterize the Order Primates. However, as research has expanded to include a number of newly studied species, such generaliza- tions about primate behavior are no longer appropriate. Data presented on the woolly spider monkey, or muriqui (Brachyteles arachnoides), provide ex- amples of the ways in which traditional views of primate behavior are being reconsidered. In muriquis, and in several other New Worm monkeys, female kin groups do not occur because females disperse from their natal groups. In addition, aggressive competition between males is virtually absent; and, female muriquis appear to be codominant with males. Constraints on sexual dimorphism may help to explain why muriquis (and other New World pri- mates) differ so fundamentally from the better known semi-terrestrial Old World monkeys. KEY WORDS: New World primates; muriqui; dispersal; sexual dimorphism; female choice 1Logo of the 1988 International Primatological Society. 2Department of Anthropology, University of Wisconsin, Madison, Wisconsin 53706. 7 0164-0291/90/0200-0007506.00/0 9 1990 Plenum Publishing Corporation