Behavioral sleep in the walrus

Pryaslova, Julia; Lyamin, Oleg I.; Siegel, Jerome M.; Mukhametov, L. M.

doi:10.1016/j.bbr.2009.01.033

Cited by 23 publications

(9 citation statements)

References 24 publications

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“…Estimates of mean fraction of time spent out of the water by walruses during summer range from one quarter to one third of the time hauled out (Hills 1992, Born et al 2005, Acquarone et al 2006, Born and Acquarone 2007, Jay et al 2001, Lydersen et al 2008. However, these studies showed considerable individual variation in haul-out activity, which was also the case in a study of four subadult walruses in captivity (Pryaslova et al 2009). Nevertheless, the fact that the adult male walrus at the Faroe Islands, even when experiencing different environmental conditions than in the Arctic, maintained the need to rest for ca.…”

Section: Swimming Speedmentioning

confidence: 75%

A note on a walrus’ European odyssey

Born

Stefansson²,

Mikkelsen³

et al. 2014

NAMMCOSP

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This study reports on the first successful identification of the site of origin of an extralimital walrus in Europe. On 24 February 2010 an adult male Atlantic walrus (Odobenus rosmarus rosmarus) migrant was instrumented with a SPOT-5 satellite-linked transmitter (SLT) while hauled out on a beach on the Faroe Islands at 62° 15' N/06° 32' W. This SLT transmitted until 5 March during which period the walrus made local movements, likely for feeding. Transmissions were not received during 6-25 March, however, visual observations during this time indicated that the walrus remained at the Faroe Islands. A second transmitter was deployed on the same animal on 25 March 2010 at another site on the islands (62° 16' N/07° 04' W). Activity data collected over 13 days indicated that the walrus hauled out in three different places in the Faroe Islands and used a total of 24% of its time resting on land. On 29 March 2010 the walrus left the Faroe Islands and headed WNW towards NE Iceland. On 2 April it took a NNE course and swam towards Svalbard where the last location was received from a sea ice covered area on 25 April 2010 at 78° 27' N/09° 20' E (i.e. ca. 40 km west of the island of Prins Karls Forland in the western Svalbard archipelago). During 29 March-22 April the walrus swam a minimum distance of 2216 km between the last location at the Faroe Islands and the first location at Svalbard, with an average swimming speed of 4.5 km/h. A genetic analysis indicated that this walrus belonged to the Svalbard-Franz Josef Land subpopulation, thereby confirming that it returned to its site of origin.

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Section: Swimming Speedmentioning

confidence: 75%

A note on a walrus’ European odyssey

Born

Stefansson²,

Mikkelsen³

et al. 2014

NAMMCOSP

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“…Additional information supporting the consistency of this behaviour pattern for walruses can be found in a study of sleep in captive walruses, in which four two-year-old walruses were videotaped continuously for 7 -17 days in a pool filled with seawater and equipped with a resting platform. The four youngsters spent an average of 75% of their time in the water (Pryaslova and Lyamin, 2006).…”

Section: Discussionmentioning

confidence: 99%

Estimating the Number of Walruses in Svalbard from Aerial Surveys and Behavioural Data from Satellite Telemetry

Lydersen¹,

Aars²,

Kovacs³

2009

ARCTIC

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ABSTRACT. All known terrestrial haul-out sites for walruses in Svalbard (n = 79) were surveyed during the period 1-3 August 2006, and sites that were in use (n = 17) were documented using digital photography. A total of 657 walruses were counted on land in the resultant images. An extensive behavioural data set from walruses equipped with satellite relay data loggers, covering August 2002 to August 2005, was used to account for walruses that were in the water. The proportion of walruses at sea during the survey was calculated to be 0.750 on the basis of 28 thirty-day periods from 23 male walruses. Time of day and wind chill did not significantly affect haul-out behaviour. However, a logistic regression model revealed both a correlation among haul-out patterns of individuals within years, and a year effect (χ 2 = 6.42, df = 2, p = 0.04). Because the survey was not flown in a year when satellite tags were deployed, the interannual variance was retained in a model (with no other explanatory variables). The overdispersion parameter from this model was 2.02 (deviance = 28.33, df = 14). Thus, variance in proportions of time individuals spent at sea was multiplied by this parameter to achieve a corrected SE around the estimate. The 95% CI based on this SE corresponded to a proportion of walruses at sea during the survey between 0.717 and 0.781, resulting in an estimated total number of walruses in Svalbard in August 2006 of 2629 (95% CI: 2318 -2998).Key words: walrus, Odobenus rosmarus, aerial survey, digital photography, satellite telemetry, haul-out behaviour, Svalbard RÉSUMÉ. Toutes les échoueries terrestres de morses connues à Svalbard (N = 79) ont été étudiées pendant la période allant du 1 er au 3 août 2006, et les échoueries utilisées (N = 17) ont été documentées à l'aide de photographies numériques. En tout, 657 morses ont été dénombrés dans les images résultantes. Une série de données exhaustives sur le comportement des morses dotés d'enregistreurs de données par satellite -données portant d'août 2002 à août 2005 -a permis de faire le compte des morses se trouvant dans l'eau. La proportion de morses à la mer pendant la période visée par l'étude a été calculée à 0,750 sur la base de 28 périodes de trente jours à partir de 23 morses mâles. Le moment de la journée et le refroidissement éolien n'ont pas exercé une grande incidence sur le comportement en échouerie. Cependant, un modèle de régression logistique a révélé une corrélation entre les tendances en échouerie d'individus en dedans de plusieurs années, ainsi qu'un effet année (χ 2 = 6,42, dl = 2, p = 0,04). Puisque l'étude n'a pas été effectuée au cours d'une année où les étiquettes satellites ont été déployées, l'écart interannuel a été conservé dans un modèle (sans aucune autre variable indépendante). Le paramètre de surdispersion découlant de ce modèle était de 2,02 (déviance = 28.33, dl = 14). Par conséquent, l'écart en proportions de temps que les individus passaient en mer a été multiplié par ce paramètre pour obtenir une erreur-type corrigée autour d...

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“…It can also be argued that animals that sleep less would exhibit less REM sleep. Although this could be true, an important interesting fact is that the majority of both [44][45][46][47][48] . Some pinnipeds, such as Caspian seals (Phoca caspica) [49] , harp seals (Pagophilus groenlandica) [50] and elephant seals (Mirounga angustirostris) [51] , do not exhibit inter-hemispheric asymmetry in slow-wave generation during NREM sleep, suggesting that unihemispheric sleep is typical of fur seals and sea lions but not of all semi-aquatic pinnipeds.…”

Section: Continuedmentioning

confidence: 99%

Sleep alterations in mammals: Did aquatic conditions inhibit rapid eye movement sleep?

Madan

Jha

2012

Neurosci. Bull.

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Sleep has been studied widely in mammals and to some extent in other vertebrates. Higher vertebrates such as birds and mammals have evolved an inimitable rapid eye movement (REM) sleep state. During REM sleep, postural muscles become atonic and the temperature regulating machinery remains suspended. Although REM sleep is present in almost all the terrestrial mammals, the aquatic mammals have either radically reduced or completely eliminated REM sleep.Further, we found a significant negative correlation between REM sleep and the adaptation of the organism to live on land or in water. The amount of REM sleep is highest in terrestrial mammals, significantly reduced in semi-aquatic mammals and completely absent or negligible in aquatic mammals. The aquatic mammals are obligate swimmers and have to surface at regular intervals for air. Also, these animals live in thermally challenging environments, where the conductive heat loss is approximately ~90 times greater than air. Therefore, they have to be moving most of the time. As an adaptation, they have evolved unihemispheric sleep, during which they can rove as well as rest. A condition that immobilizes muscle activity and suspends the thermoregulatory machinery, as happens during REM sleep, is not suitable for these animals. It is possible that, in accord with Darwin's theory, aquatic mammals might have abolished REM sleep with time. In this review, we discuss the possibility of the intrinsic role of aquatic conditions in the elimination of REM sleep in the aquatic mammals.

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Behavioral sleep in the walrus

Cited by 23 publications

References 24 publications

A note on a walrus’ European odyssey

A note on a walrus’ European odyssey

Estimating the Number of Walruses in Svalbard from Aerial Surveys and Behavioural Data from Satellite Telemetry

Sleep alterations in mammals: Did aquatic conditions inhibit rapid eye movement sleep?

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