The effects of age on behavioral thermoregulation in Lemur catta and Propithecus coquereli

Abstract

Older mammals experience a decrease in physiological function that impairs their ability to internally regulate body temperature. Behavioral mechanisms can be used to alleviate thermal stress on the body, and thus could be an effective strategy for coping with such deficiencies that accompany the aging process. I studied geriatric and younger individuals of five semi-free ranging groups of Lemur catta and Propithecus coquereli to determine whether or not older lemurs were utilizing behavioral thermoregulation more often than younger lemurs across a range of temperatures. Using focal animal sampling, I examined activity level, the use of heat-retaining and heat-dissipating postures, and sun exposure preference. I found that older lemurs changed their own behavior more than younger individuals to utilize low-energy thermoregulatory behaviors, such as decreasing activity level as temperature increased, shifting to utilize heat-retaining postures in cooler temperatures, and shifting to utilize heat-dissipating postures in warmer temperatures. These patterns, however, were not statistically significant and therefore only suggestive of their function in varying ambient temperatures. Still, this information is useful preliminary data, and future study with more focal individuals over a wider range of temperatures may be able to highlight these subtle, but potentially meaningful differences between age classes. By examining the thermoregulatory potential of all members of lemur social groups we can make more informed conservation decisions for these species in changing climatic environments.