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Student Prize Award Abstract
1996 Poster Paper Honorable Mention


J.C. Bicca-Marques and C. Calegaro-Marques
Department of Anthropology, University of Illinois, Urbana, IL 61801, U.S.A.

Behavioral thermoregulation in primates has been related to the dissipation of heat during periods of high ambient temperature, heat conservation under cold conditions, and food shortage. This research is the first to focus on the use of thermoregulatory behaviors by a highly sexually dichromatic primate. Five hypothesis on the influence of (1) postures, (2) microhabitat selection, (3) particular body region exposed to sunlight, (4) coat coloration, and (5) body size on the thermoregulatory behavior in relation to the thermal environment were tested. This study was conducted in a seminatural 2 ha forest located in a region of subtropical climate in Brazil. During one year, behavioral data were collected in a habituated group of 15-17 individuals. All age-sex classes were represented. Data on body posture, presence of sun, place, and body portion exposed to sunlight were recorded during resting. Ambient temperature was measured each hour and ranged from 5 to 35C. Black howlers showed a consistent use of heat conservative postures (>83% of the records), sunny places (>81%), and the exposure of the ventral region to sunlight during resting under low ambient temperatures (5-15C). The opposite occurred under high ambient temperatures. Despite the striking difference in color between adults, and the differences in size between age classes, no significant differences were detected in postural-positional thermoregulatory behaviors. The importance of these behaviors to the energy budget and digestive efficiency of this folivorous neotropical primate are discussed. Finally, issues for future research are proposed. We acknowledge the University of Brasilia, National Research Council (CNPq-Brazil), and World Fund-U.S. for logistical and financial support.

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