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Las ballenas del Golfo de California

Publisher: Secretaría de Medio Ambiente y Recursos Naturales, ISBN: 968817761X
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    ABSTRACT: The trophic position and the predator–prey relationship between the sperm whale Physeter macrocephalus and the jumbo squid Dosidicus gigas were examined by measuring stable isotope ratios of carbon and nitrogen. Skin samples of sperm whales and muscle samples of small and large jumbo squid were collected between 1996 and 1999 in the Gulf of California. Gender determination through molecular analysis and field identification of size were used to identify adult male, female and immature male sperm whales. The stable isotope ratios of C and N of females and immature males were significantly different from those of adult male sperm whales; however, between females and immature males they did not differ significantly. The δ13C and δ15N values of females and immature males were higher than large jumbo squid by 1.1‰ and 2.7‰ respectively, suggesting a predator–prey relationship between them. A low isotopic interannual variation among the years 1997 to 1999 was observed in the isotopic signature of females and males. Adult males exhibited a lower isotopic signature than females and immature males, and did not show a trophic relationship with D. gigas. We hypothesized that the stable isotopic signature of mature males reflected their diet from an earlier high-latitude feeding ground. This study shows that stable isotope analysis of sloughed skin samples from free-ranging sperm whales can be an alternative method to stomach content and fecal analyses for evaluating trophic relationships
    Marine Ecology Progress Series 01/2004; 277::275-283. · 2.64 Impact Factor
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    ABSTRACT: The grouping behaviour of animals is governed by intrinsic and extrinsic factors which play an important role in shaping their social organization. We investigated the influence of ocean climate variation on the grouping behaviour of two widely separated populations of cetaceans, inhabiting north Atlantic and north Pacific coastal waters. The group size of both bottlenose dolphins in the Moray Firth, UK, and killer whales in Johnstone Strait, Canada, varied from year to year in relation to large-scale ocean climate variation. Local indices of prey abundance were also related both to climate indices and predator group sizes. The cetaceans tended to live in smaller groups when there was less salmon available in both areas which seem to occur 2 years after a lower phase of the North Atlantic and Pacific Decadal Oscillations. These findings suggest that, even in highly social mammals, climate variation may influence social organization through changes in prey availability.
    Ecology Letters 10/2004; 7(11):1068 - 1076. · 17.95 Impact Factor
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    Nature 02/2002; 415(6868):106. · 38.60 Impact Factor

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