Ecology and neurophysiology of sleep in two wild sloth species

Study Objectives: Interspecific variation in sleep measured in captivity correlates with various physiological and environmental factors, including estimates of predation risk in the wild. However, it remains unclear whether prior comparative studies have been confounded by the captive recording environment. Herein we examine the impact of predation pressure on sleep in sloths living in the wild. Design: Comparison of two closely related sloth species, one exposed to predation and one free from predation. Setting: Panamanian mainland rainforest (predators present) and island mangrove (predators absent). Participants: Mainland (Bradypus variegatus, 5 males and 4 females) and island (Bradypus pygmaeus, 6 males) sloths. Interventions: None. Measurements and Results: EEG and EMG activity were recorded using a miniature data logger. Although both species spent between 9 and 10 hours per day sleeping, the mainland sloths showed a preference for sleeping at night, whereas island sloths showed no preference for sleeping during the day or night. EEG activity during NREM sleep showed lower low-frequency power, and increased spindle and higher frequency power in island sloths when compared to mainland sloths. Conclusions: In sloths sleeping in the wild, predation pressure influenced the timing of sleep, but not the amount of time spent asleep. The preference for sleeping at night in mainland sloths may be a strategy to avoid detection by nocturnal cats. The pronounced differences in the NREM sleep EEG spectrum remain unexplained, but might be related to genetic or environmental factors.

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Affiliation: Sophie Broussau, Amelie Pilotte & Bernard Massie : Départment de microbiologie et immunologie, Faculté de médecine, Université de Montréal

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Affiliation: Svetlana Shumikhina &Stéphane Molotchnikoff : Département de Sciences Biologiques, Université de Montréal

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Affiliation: Paul Allard : Département de kinésiologie, Université de Montréal

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Affiliation: Mark Daniel : Département de médecine sociale et préventive, Faculté de médecine, Université de Montréal

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Affiliation: Institut de recherche en immunologie et en cancérologie, Université de Montréal

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Affiliation: Johanne Renaud & Claude Marquette : CHU Ste-Justine, Université de Montréal

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Affiliation: Augustin Zeba & Hélène Delisle : Département de nutrition, Faculté de médecine, Université de Montréal

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Affiliation: Département de Psychologie, Université de Montréal

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Affiliation: Henner Brinkmann : Département de biochimie, Faculté de médecine, Université de Montreal

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Affiliation: Faculté de médicine, Université de Montréal

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Affiliation: Louise Potvin: Groupe de recherche interdisciplinaire en santé, Faculté de médecine, Université de Montréal

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Affiliation: Département de Biochimie, Faculté de médecine, Université de Montréal

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Affiliation: Pierre Dagenais : Hôpital Maisonneuve-Rosemont, Faculté de médecine, Université de Montréal

Mechanisms of lipid malabsorption in Cystic Fibrosis: the impact of essential fatty acids deficiency

Affiliation: CHU-Sainte-Justine, Université de Montréal