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Haul‐out and diving activity of male Atlantic walruses ( Odobenus rosmarus rosmarus ) in NE Greenland
Author(s) -
Born E. W.,
Knutsen L. Ø
Publication year - 1997
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1997.tb02789.x
Subject(s) - foraging , range (aeronautics) , evening , oceanography , biology , geology , ecology , materials science , physics , astronomy , composite material
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.