title: Ecology and neurophysiology of sleep in two wild sloth species.
abstract: OBJECTIVE
  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 effect of predation pressure on sleep in sloths living in the wild.
  
  
  METHODS
  Comparison of two closely related sloth species, one exposed to predation and one free from predation.
  
  
  METHODS
  Panamanian mainland rainforest (predators present) and island mangrove (predators absent).
  
  
  METHODS
  Mainland (Bradypus variegatus, five males and four females) and island (Bradypus pygmaeus, six males) sloths.
  
  
  METHODS
  None.
  
  
  RESULTS
  Electroencephalographic (EEG) and electromyographic (EMG) activity was recorded using a miniature data logger. Although both species spent between 9 and 10 h 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. Standardized EEG activity during nonrapid eye movement (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.
authors.affiliation: Avian Sleep Group, Max Planck Institute for Ornithology - Seewiesen, Seewiesen, Germany ; Department of Migration and Immuno-Ecology, Max Planck Institute for Ornithology - Radolfzell, Radolfzell, Germany ; Smithsonian Tropical Research Institute - Panama, Balboa, Ancón, Panama.
authors.forename: Bryson
authors.initials: B
authors.lastname: Voirin
authors.affiliation: Avian Sleep Group, Max Planck Institute for Ornithology - Seewiesen, Seewiesen, Germany ; Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
authors.forename: Madeleine F
authors.initials: MF
authors.lastname: Scriba
authors.affiliation: Avian Sleep Group, Max Planck Institute for Ornithology - Seewiesen, Seewiesen, Germany.
authors.forename: Dolores
authors.initials: D
authors.lastname: Martinez-Gonzalez
authors.affiliation: Institute of Neuroinformatics, University of Zurich and Swiss Federal Institute of Technology (ETH), Zurich, Switzerland.
authors.forename: Alexei L
authors.initials: AL
authors.lastname: Vyssotski
authors.affiliation: Department of Migration and Immuno-Ecology, Max Planck Institute for Ornithology - Radolfzell, Radolfzell, Germany ; Department of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wikelski
authors.affiliation: Avian Sleep Group, Max Planck Institute for Ornithology - Seewiesen, Seewiesen, Germany.
authors.forename: Niels C
authors.initials: NC
authors.lastname: Rattenborg
mesh_terms: D000818:Animals; D000835:Animals, Wild / Q000502:physiology* / Q000523:psychology; D001143:Arousal / Q000502:physiology; D001569:Benzodiazepines / Q000378:metabolism; D004032:Diet / Q000662:veterinary; D004569:Electroencephalography; D004576:Electromyography; D045989:Felidae / Q000502:physiology; D005260:Female; D062312:Islands; D008297:Male; D010176:Panama; D011235:Predatory Behavior; D065947:Rainforest; D012890:Sleep / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D012896:Sloths / Q000502:physiology* / Q000523:psychology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology
chemical_list: D001569:Benzodiazepines
keywords: Benzodiazepine; EEG; NREM sleep; REM sleep; phasing; predation; sloth; spindle; wild