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, inter-daily activity stability, and intra-daily activity variability of individuals in simultaneous experiments of sleep-site enrichment and sleep-site impoverishment. Over 164 24-hour periods from 8 individuals (2 of each species), we found evidence that enriched sleep-sites increased daily sleep times of lemurs, with an average increase of thirty-two minutes. The effect of sleep-site impoverishment was small and not statistically significant. Though our experimental manipulations altered inter-daily stability and intra-daily variability in activity patterns relative to baseline, the changes did not differ significantly between enriched and impoverished conditions. 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.

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.

Effects of scent enrichment on behavioural and physiological indicators of stress in zoo primates – a preliminary study on red-ruffed lemurs and Lar gibbons

Almost half of the primate species recognized today worldwide are classified as endangered or critically endangered in the wild. Captive breeding is vital for primate conservation, with modern zoos serving a crucial role as breeders of populations acting as buffers against extinction, ambassadors of endangered species, and educators of the general public. However, captive populations may experience welfare issues that may also undermine their breeding success. In order to design and test a new scent enrichment programme to enhance the breeding success and well-being of critically endangered zoo primates, we carried out a preliminary study to assess the effects of lavender on captive red-ruffed lemurs (Varecia rubra) and Lar gibbons (Hylobates lar) as these species presently show a low success rate in captive breeding and are critically endangered in the wild. We combined behavioural observations and faecal endocrinology analyses to assess the effects of lavender on two captive troops (N = 8) housed at Dudley Zoo and Castle (UK). We recorded observations of natural species-specific and abnormal stress-related behaviours for 144 hr using instantaneous scan sampling. We collected 78 faecal samples and measured the faecal cortisol concentrations using radioimmunoassay. We found a significant effect by the scent enrichment on social interactions and stress-related behaviours (i.e., pacing and self-scratching), with both species reducing their rates of stress-related behaviours after they were exposed to lavender. We also found that both species displayed a significant increase in faecal glucocorticoids following the exposure to lavender. Our findings suggest that lavender may work as scent enrichment to decrease the stress levels of zoo primates across the major lineages, but its effects might change depending on the species-specific social lives and olfactory repertoires of primates.

Grasping pressures and phalangeal curvature in primates : an experimental in vivo approach

Phalangeal curvature is often used to infer arboreal locomotion in fossil primate species. This is based off an hypothesis of plasticity linked to a loading model that suggests that, when flexed during grasping, a curved phalanx will experience lower internal strains than a straight phalanx. This dissertation is the first in vivo test of this hypothesis. By examining grasping pressures exerted by individual manual and pedal digits during above-branch, below-branch and vertical-branch locomotion, and comparing those pressures to proximal manual and pedal phalangeal curvature, a number of well-accepted but untested hypotheses regarding the relationship between digital form and grasping were tested. 4 adults (2 males, 2 females) each from 4 species of lemur (Lemur catta, Propithecus coquereli, Varecia rubra) were induced to cross an artificial substrate instrumented with a pressure pad at the stated orientations. Digital pressures were then compared to the proximal phalangeal curvature of the same individuals. Findings do not demonstrate any relationship between arboreal grasping at any orientation and digital pressures. This project fails to support previously long-held hypotheses regarding the biological role of phalangeal curvature, and introduces the strong likelihood that a much more complex model of loading is necessary to understand primate phalangeal curvature. Until such a model is devised and tested, using phalangeal curvature to infer arboreal behavior is unsupportable, and should be avoided.