Contract grant sponsor: National Science Foundation, contract grant numbers: SGER BNS 97-11124; BCS 98-15991; Contract grant sponsor: Semliki Chimpanzee Project; Contract grant sponsor: Indiana University.
A Thermodynamic Comparison of Arboreal and Terrestrial Sleeping Sites for Dry-Habitat Chimpanzees (Pan troglodytes schweinfurthii) at the Toro-Semliki Wildlife Reserve, Uganda
Version of Record online: 2 MAY 2012
© 2012 Wiley Periodicals, Inc.
American Journal of Primatology
Volume 74, Issue 9, pages 811–818, September 2012
How to Cite
SAMSON, D. R. and HUNT, K. D. (2012), A Thermodynamic Comparison of Arboreal and Terrestrial Sleeping Sites for Dry-Habitat Chimpanzees (Pan troglodytes schweinfurthii) at the Toro-Semliki Wildlife Reserve, Uganda. Am. J. Primatol., 74: 811–818. doi: 10.1002/ajp.22031
- Issue online: 17 JUL 2012
- Version of Record online: 2 MAY 2012
- Manuscript Accepted: 11 MAR 2012
- Manuscript Revised: 8 MAR 2012
- Manuscript Received: 22 AUG 2011
- National Science Foundation. Grant Numbers: SGER BNS 97-11124, BCS 98-15991
- Semliki Chimpanzee Project
- Indiana University
The nightly construction of an arboreal sleeping platform (SP) has been observed among every chimpanzee's population studied to date. Here, we report on bioclimatic aspects of SP site choice among dry-habitat chimpanzees (Pan troglodytes schweinfurthii) at the Toro-Semliki Wildlife Reserve, Uganda. We placed a portable weather monitor within 1 m of chimpanzee SPs and compared the microenvironment of this site with terrestrial monitors placed 10 cm above the ground directly underneath the simultaneously studied SP. We calculated physical “comfort levels” of monitored sites using the RayMan thermophysiological model that we modified to take ape body proportions into account. The RayMan tool gauges energy balance using wind speed, temperature, relative humidity, and heat index in conjunction with the study subject's mass and stature to determine whether the individual is in energy balance or homeostasis. We found that (1) terrestrial microclimates have greater homeostatic potential than arboreal microclimates, and (2) there is a significant positive linear relationship between wind speed and height of SP in the forest canopy. Advantages of terrestrial sites are that they require lesser energetic expenditure to stabilize the body when the SP is under construction and perhaps during use as well. We found that terrestrial sites also had better homeostatic potentials. This combination of advantages explains why SPs are so often sited terrestrially in habitats where predation risk is low. Early hominins must have had technological or social measures to avoid or deter predators that were significantly advanced over those found among chimpanzees before they began sleeping on the ground. Am. J. Primatol. 74:811–818, 2012. © 2012 Wiley Periodicals, Inc.