Enriched sleep environments lengthen lemur sleep duration

Characteristics of the sleep-site are thought to influence the quality and duration of primate sleep, yet only a handful of studies have investigated these links experimentally. Using actigraphy and infrared videography, we quantified sleep in four lemur species (Eulemur coronatus, Lemur catta, Propithecus coquereli, and Varecia rubra) under two different experimental conditions at the Duke Lemur Center (DLC) in Durham, NC, USA. Individuals from each species underwent three weeks of simultaneous testing to investigate the hypothesis that comfort level of the sleep-site influences sleep. We obtained baseline data on normal sleep, and then, in a pair-wise study design, we compared the daily sleep times of individuals in simultaneous experiments of sleep-site enrichment and sleep-site impoverishment. Over 163 24-hour periods from 8 individuals (2 of each species), we found strong evidence that enriched sleep-sites increased daily sleep times of lemurs, with an average increase of thirty-one minutes. The effect of sleep-site impoverishment was small and not statistically significant. We conclude that properties of a sleep-site enhancing softness or insulation, more than the factors of surface area or stability, influence lemur sleep, with implications regarding the importance of nest building in primate evolution and the welfare and management of captive lemurs.