Haul‐out and diving activity of male Atlantic walruses ( Odobenus rosmarus rosmarus ) in NE Greenland

Autor: L. Ø Knutsen, E. W. Born
Rok vydání: 1997
Předmět:
Zdroj: Journal of Zoology. 243:381-396
ISSN: 1469-7998
0952-8369
DOI: 10.1111/j.1469-7998.1997.tb02789.x
Popis: During August-September 1989 and 1990, movements, haul out and dive activity of male Atlantic walruses (Odobenus rosmarus rosmarus L.) were studied at a terrestrial haul-out site situated in an inshore foraging area in NE Greenland at 76± 30′ N. Data were collected from direct observations of a group of about 50 males during August, including walruses that could be individually identified from natural markings, and from tracking of 8 adults equipped with satellite-linked radio transmitters during August-September. In both years, instrumented walruses hauled out for a total of 29.3% of the sampling time. In 1989, when ice floes were available for hauling out, the walruses spent 11% of the time on ice, whereas in 1990, when ice was absent from the study area, they only hauled out on land. Duration of haul-out periods, which did not differ between months or years, averaged 11 h (0.46 d) on ice (S.D. = 5.9, range: 1–29 h, n= 19 periods), and 38 h (1.6 d) on land (S.D. = 11.7, range: 13–64 h, n= 43). The walruses mainly hauled out during the afternoon and evening. Numbers hauling out on land during August were negatively correlated with wind direction, precipitation (rain) and wind-chill. In 1989, the duration of periods of absence from the terrestrial haul-out site (i.e. presumed foraging trips) averaged 206 h or 8.5 d (S.D. = 106.9, range: 48–412 h, n= 13), whereas, in 1990, such trips averaged only 81 h or 3.4 d (S.D. = 37.9, range: 24-156 h, n= 24), reflecting that walruses used the haul-out site more frequently when ice was absent. Direct observations of foraging walruses showed that they were submerged about 81% of the time.
Databáze: OpenAIRE
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