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The ontogeny of diving behaviour in New Zealand fur seal pups (Arctocephalus forsteri)

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Abstract:

This study investigated the development of diving in 21 New Zealand fur seal pups, Arctocephalus forsteri (Lesson, 1828), prior to weaning at Cape Gantheaume, Kangaroo Island. Diving behaviour was examined using time–depth recorders, which were deployed during two time periods, 5 months prior to weaning (n = 6) and 2 months prior to weaning (n = 15). Scats were also examined to assess whether fur seal pups foraged prior to weaning. The maximum dive depth attained was 44 m, while the maximum dive duration was 3.3 min. Immediately prior to weaning, fur seal pups spent a greater proportion of their time diving at night, and concomitantly several measures of diving performance also increased. In general, pups dived successively deeper (6–44 m between June and September), and the average number of dives per day, dive frequency, and vertical distance travelled increased. Prey remains were present in approximately 30% of scats and indicated that some pups were foraging as early as June (5–6 months of age, approximately 4–5 months prior to weaning). Of the scats that contained prey remains, fish (South American pilchard, Sardinops sagax (Jenyns, 1842); Australian anchovy, Engraulis australis (White, 1790); and redbait, Emmelichthys nitidus Richardson, 1845) accounted for 43% of the prey items found, crustaceans accounted for 36%, and cephalopods (Gould's squid, Nototodarus gouldi (McCoy, 1888)) accounted for 20%.

Notre étude examine le développement de la plongée chez 21 jeunes otaries d'Australie (Arctocephalus forsteri (Lesson, 1828)) avant le sevrage au cap Gantheaume, Ile Kangourou. Nous avons étudié le comportement de plongée à l'aide d'enregistreurs de plongée (temps et profondeur) qui ont été déployés à deux périodes, soit 5 mois (n = 6) et 2 mois (n = 15) avant le sevrage. Nous avons aussi analysé les défécations pour déterminer si les petits recherchent de la nourriture avant le sevrage. La profondeur maximale atteinte est de 44 m et la durée maximale d'une plongée est de 3,3 min. Dans la période qui précède immédiatement le sevrage, les jeunes otaries passent une plus grande partie de leur temps à des plongées nocturnes et, en même temps, plusieurs mesures de leur performance de plongée augmentent. En général, les jeunes plongent de plus en plus profondément (6–44 m de juin à septembre) et leur nombre moyen de plongées quotidiennes, la fréquence des plongées et la distance verticale parcourue augmentent. Des restes de proies se retrouvent dans à peu près 30 % des défécations, ce qui indique que certains jeunes s'alimentent dès le mois de juin (à l'âge de 5–6 mois, environ 4–5 mois avant le sevrage). Les poissons (la sardine du Cap, Sardinops sagax (Jenyns, 1842), l'anchois, Engraulis australis (White, 1790) et l'andorrève du Cap, Emmelichthys nitidus Richardson, 1845) représentent 43 % des morceaux de proies retrouvés dans les défécations qui en contiennent, alors que les crustacés en représentent 36 % et les céphalopodes (les encornets éventails, Notodarus gouldi (McCoy, 1888)) 20 %.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: September 1, 2005

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  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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