Student Prize Award Abstract
1996 Poster Paper Honorable Mention
THERMOREGULATORY BEHAVIOR IN A SEXUALLY DICHROMATIC NEOTROPICAL PRIMATE. THE BLACK HOWLER MONKEY (Alouatta caraya)
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 35°C. 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 (5-15°C). 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.