We investigated sleep in therock hyrax, Procavia capensis, a social mammal that typically lives in colonies on rocky outcrops throughout most parts of Southern Africa. The sleep of 5 wild-captured, adult rock hyraxes was recorded continuously for 72 h using telemetric relay of signals and allowing unimpeded movement. In addition to waking, slow wave sleep (SWS) and an unambiguous rapid eye movement (REM) state, a sleep state termed somnus innominatus (SI), characterized by low-voltage, high-frequency electroencephalogram, an electromyogram that stayed at the same amplitude as the preceding SWS episode and a mostly regular heart rate, were identified. If SI can be considered a form of low-voltage non-REM, the implication would be that the rock hyrax exhibits the lowest amount of REM recorded for any terrestrial mammal studied to date. Conversely, if SI is a form of REM sleep, it would lead to the classification of a novel subdivision of this state; however, further investigation would be required. The hyraxes spent on average 15.89 h (66.2%) of the time awake, 6.02 h (25.1%) in SWS, 43 min (3%) in SI and 6 min (0.4%) in REM. The unambiguous REM sleep amounts were on average less than 6 min/day. The most common state transition pathway in these animals was found to be wake → SWS → wake. No significant differences were noted with regard to total sleep time, number of episodes and episode duration for all states between the light and dark periods.Thus, prior classification of the rock hyrax as strongly diurnal does not appear to hold under controlled laboratory conditions.

Affanni JM (1972): Observations on the sleep of some South American marsupials and edentates; in Chase M (ed): The Sleeping Brain. Los Angeles, Brain Research Institute, University of California, pp 21–23.
Allison T, Cicchetti PV (1976): Sleep in mammals: ecological and constitutional correlates. Science 194:732–734.
Berger RJ, Walker JM (1972): A polygraphic study of sleep in the tree shrew (Tupaia glis). Brain Behav Evol 5:54–69.
Bergmann BM, Winter JB, Rosenberg RS, Rechtschaffen A (1987): NREM sleep with low-voltage EEG in the rat. Sleep 10:1–11.
Campbell SS, Tobler I (1984): Animal sleep: a review of sleep duration across phylogeny. Neurosci Biobehav Rev 8:296–300.
Capellini I, Barton RA, McNamara P, Preston BT, Nunn CL (2008): Phylogenetic analysis of the ecology and evolution of mammalian sleep. Evolution 62:1764–1776.
Cirelli C, Tononi G (2008): Is sleep essential? PLoS Biol 6:e216.
de Moura Filho AG, Huggins SE, Lines SG (1983): Sleep and waking in the three-toed sloth Bradypus tridactylus. Comp Biochem Physiol A 76:345–355.
Desiraju T, Anand BK, Singh B (1966): Electrographic studies on the nature of sleep and wakefulness. Physiol Behav 1:285–291.
Elgar MA, Pagel MD, Harvey PH (1988): Sleep in mammals. Anim Behav 36:1407–1419.
Gottesman C (1992): Detection of seven sleep-waking stages in the rat. Neurosci Biobehav Rev 16:31–38.
Hallström BM, Kullberg M, Nilsson MA, Janke A (2007): Phylogenomic data analyses provide evidence that Xenarthra and Afrotheria are sister groups. Mol Biol Evol 24:2059–2068.
Hartman DS (1979): Ecology and Behavior of the Manatee (Trichechus manatus) in Florida. Pittsburgh, American Society of Mammalogists.
Horne J (2009): REM sleep, energy balance and ‘optimal foraging’. Neurosci Behav Rev 33:466–474.
Kingdon J (1971): East African Mammals – An Atlas of Evolution in Africa. London, Academic Press.
Kurt F (1960): Le sommeil des éléphants. Mammalia 24:259–272.
Lesku JA, Bark RJ, Martinez-Gonzalez D, Rattenborg NC, Amlaner CJ, Lima SL (2008): Predator-induced plasticity in sleep architecture in wild-caught Norway rats (Rattus norvegicus). Behav Brain Res 189:298–305.
Lyamin OI, Kosenko PO, Lapierre JL, Mukhametov LM, Siegel JM (2008a): Fur seals display a strong drive for bilateral slow-wave sleep while on land. J Neurosci 28:12614–12621.
Lyamin OI, Lapierre JL, Kosenko PO, Mukhametov LM, Siegel JM (2008b): Electroencephalogram asymmetry and spectral power during sleep in the northern fur seal. J Sleep Res 17:154–165.
Lyamin OI, Manger PR, Ridgway SH, Mukhametov LM, Siegel JM (2008c): Cetacean sleep: an unusual form of mammalian sleep. Neurosci Biobehav Rev 32:1451–1484.
McNamara P, Capellini I, Harris E, Nunn CL, Barton RA, Preston B (2008): The phylogeny of sleep database: a new resource for sleep scientists. Open Sleep J 1:11–14.
Moss C (1982): Portraits in the Wild. Chicago, University of Chicago Press.
Mukhametov LM, Lyamin OI, Chetyrbok IS, Vassilyev AA, Diaz RP (1992): Sleep in an Amazonian manatee, Trichechus inunguis. Experientia 48:417–419.
Nicolau MC, Akaârir M, Gamundí A, Gonzáles J, Rial RV (2000): Why we sleep: the evolutionary pathway to the mammalian sleep. Prog Neurobiol 62:379–406.
Nowak RM (1999): Walker’s Mammals of the World, ed 6. Baltimore, Johns Hopkins, vol 2.
Olds N, Shoshani J (1982): Procavia capensis. Mammalian Species 171:1–7.
Pivik RT, Sircar S, Braun C (1981): Nuchal muscle tonus during sleep, wakefulness and tonic immobility in the rabbit. Physiol Behav 26:13–20.
Rattenborg NC, Voirin B, Vyssotski AL, Kays RW, Spoelstra K, Kuemmeth F, Heidrich W, Wikelski M (2008): Sleeping outside the box: electroencephalographic measures of sleep in sloths inhabiting a rainforest. Biol Lett 4:402–405.
Rial RV, Akaârir M, Gamundí A, Nicolau C, Garau C, Aparicio S, Tejada S, Gené L, González J, De Vera LM, Coenen AM, Baraceló P, Esteban S (2010): Evolution of wakefulness, sleep and hibernation: from reptiles to mammals. Neurosci Biobehav Rev 34:1144–1160.
Siegel JM (2005a): Clues to the function of mammalian sleep. Nature 437:1264–1271.
Siegel JM (2005b): REM Sleep; in Kryger MH, Roth R, Dement WC (eds): Principles and Practices of Sleep Medicine, ed 4. New York, Saunders.
Siegel JM (2008): Do all animals sleep? Trends Neurosci 31:208–213.
Siegel JM (2009): Sleep viewed as a state of adaptive inactivity. Nat Rev Neurosci 10:747–753.
Siegel JM, Manger PR, Nienhuis R, Fahringer HM, Pettigrew JD (1999): Sleep in the platypus. Neuroscience 91:391–400.
Skinner JD, Chimimba CT (2005): The Mammals of the Southern African Subregion, ed 3. Cape Town, Cambridge University Press.
Snyder F (1974): Sleep-waking patterns of Hyracoidea. Sleep Res 3:87.
Snyder F, Bugbee N, Douthitt T (1972): Telemetric studies of 24-hour sleep-waking patterns in some primitive mammals. Psychophysiology 9:122.
Steriade M (2005): Brain electrical activity and sensory processing during waking and sleeping states; in Kryger MH, Roth R, Dement WC (eds): Principles and Practices of Sleep Medicine, ed 4. New York, Saunders.
Sunquist M, Montgomery G (1973): Activity patterns and rates of movement of two-toed and three-toed sloths, Choloepushoffmani and Bradypus infuscatus. J Mammal 54:946–954.
Tabuce R, Asher RJ, Lehmann T (2008): Afrotherian mammals: a review of current data. Mammalia 72:2–14.
Tobler I (1992): Behavioral sleep in the Asian elephant in captivity. Sleep 15:1–12.
Tobler I (1995): Is sleep fundamentally different between mammalian species? Behav Brain Res 69:35–41.
Tobler I (2005): Phylogeny of sleep regulation; in Kryger MH, Roth R, Dement WC (eds): Principles and Practices of Sleep Medicine, ed 4. New York, Saunders.
Van Twyver H, Allison T (1974): Sleep in the armadillo Dasypus novemcinctus at moderate and low ambient temperatures.Brain Behav Evol9:107–120.
Wilson ML, Bashaw MJ, Fountain K, Kieschnick S, Maple TL (2006): Nocturnal behavior in a group of female African elephants. Zoo Biol 25:173–186.
Wyatt JR, Eltringham SK (1974): The daily activity of the elephant in the Rwenzori National Park, Uganda. East Afr Wildl J 12:213–289.
Zepelin H, Siegel JM, Tobler I (2005): Mammalian sleep; in Kryger MH, Roth R, Dement WC (eds): Principles and Practices of Sleep Medicine, ed 4. New York, Saunders.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.