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Study of sleep in a walrus


Lyamin, O I; Kosenko, P O; Vyssotski, A L; Lapierre, J L; Siegel, J M; Mukhametov, L M (2012). Study of sleep in a walrus. Doklady biological sciences : proceedings of the Academy of Sciences of the USSR, Biological sciences sections / translated from Russian, 444(1):188-191.

Abstract

Several behavioral and physiological adaptations have been developed in evolution of Pinnipeds allowing them to sleep both on land and in water. To date sleep has been examined in detail in eared and true seals (the families of Otariidae and Phocidae). The aim of this study was to examine sleep in another semiaquatic mammal — the walrus, which is the only extant representative of the family Odobenidae. Slow wave and paradoxical sleep (SWS and PS) in the examined walrus (2 year old female, weight 130 kg) averaged 19.4 ± 2.0 and 6.9 ± 1.1% of 24-h when on land, and 20.5 ± 0.8% of 24-h and 1.1 ± 0.6% when in water, respectively. The average duration of PS episode was 6.4 ± 0.6 min (maximum 23 min) when on land and 1.8 ± 0.1 min (maximum 3.3 min) when in water. In water, sleep occurred predominantly while the walrus submerged and lay on the bottom of the pool (89% of total sleep time). The walrus usually woke up while emerging to the surface for breathing. Most often EEG slow waves developed synchronously in both cortical hemispheres (90% of SWS time when on land and 97% when in water). Short episodes of interhemispheric EEG asymmetry usually coincided with brief opening of one eye. The pattern of sleep in the walrus was similar to the pattern of sleep in the Otariidae seals while on land (predominantly bilateral SWS, accompanied by regular breathing) and to the pattern of sleep in the Phocidae while in water (sleep during apneas both in depth and at the surface, interrupted by brief arousal when emerging for breathing).

Abstract

Several behavioral and physiological adaptations have been developed in evolution of Pinnipeds allowing them to sleep both on land and in water. To date sleep has been examined in detail in eared and true seals (the families of Otariidae and Phocidae). The aim of this study was to examine sleep in another semiaquatic mammal — the walrus, which is the only extant representative of the family Odobenidae. Slow wave and paradoxical sleep (SWS and PS) in the examined walrus (2 year old female, weight 130 kg) averaged 19.4 ± 2.0 and 6.9 ± 1.1% of 24-h when on land, and 20.5 ± 0.8% of 24-h and 1.1 ± 0.6% when in water, respectively. The average duration of PS episode was 6.4 ± 0.6 min (maximum 23 min) when on land and 1.8 ± 0.1 min (maximum 3.3 min) when in water. In water, sleep occurred predominantly while the walrus submerged and lay on the bottom of the pool (89% of total sleep time). The walrus usually woke up while emerging to the surface for breathing. Most often EEG slow waves developed synchronously in both cortical hemispheres (90% of SWS time when on land and 97% when in water). Short episodes of interhemispheric EEG asymmetry usually coincided with brief opening of one eye. The pattern of sleep in the walrus was similar to the pattern of sleep in the Otariidae seals while on land (predominantly bilateral SWS, accompanied by regular breathing) and to the pattern of sleep in the Phocidae while in water (sleep during apneas both in depth and at the surface, interrupted by brief arousal when emerging for breathing).

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Neuroinformatics
Dewey Decimal Classification:570 Life sciences; biology
Language:English
Date:2012
Deposited On:07 Mar 2013 09:50
Last Modified:07 Dec 2017 20:20
Publisher:M A I K Nauka - Interperiodica
Number of Pages:4
ISSN:0012-4966
Publisher DOI:https://doi.org/10.1134/S0012496612030143

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