Exploration during early life: distribution, habitat and orientation preferences in juvenile king penguins
Résumé
Background: The early life of marine apex predators is poorly known, particularly for diving species. The orientation
and foraging skills are presumably less developed in juveniles than in adults, especially during their first year at sea
when juveniles might disperse further than adults.
Methods: Over two years of monitoring, we tracked the movements of 17 juvenile king penguins (Aptenodytes
patagonicus, ~ 1 year old) using satellite relay tags from Crozet Archipelago (Southern Indian Ocean), starting when
birds left their natal colony for the first time. For comparison we also tagged 6 non-breeding adults, which at that
stage, similar to juveniles, are unhampered by reproductive constraints and might roam further than breeders. We
used a combination of cluster analysis and habitat modelling to investigate and compare the movement patterns
and habitat use of experienced (non-breeding adults) and non-experienced (juveniles) individuals.
Results: While juvenile penguins and non-breeding adults followed similar routes, the movements by adults started
later in the season and ranged over a considerably smaller area than juveniles. Net squared displacement analysis
revealed that both groups did not move to a specific wintering area. Changes in direction of juveniles in respect to
their departure island were similar and synchronous for both years. Habitat models revealed that foraging
behaviour was affected by environmental variables such as wind or current speeds, sea surface temperature, or
oceanic productivity, for both stages. Analysis of tracks revealed that birds moved predominately perpendicular or
against the main direction of the Antarctic Circumpolar Current and the prevailing wind during austral summer
(juveniles only) and autumn (juveniles and non-breeding adults). However, both juveniles and adults were more
likely to move against the prevailing winds if productivity increased along their trajectories.
Conclusions: The exceptional duration of our tracking study provided unprecedented insights into the distribution,
habitat preferences and orientation of two poorly known life history stages of an expert avian diver. Our study
suggests that juveniles might use both innate and learnt skills to reach profitable foraging areas during their first
year at sea, which is critical in long-lived species.
Origine | Fichiers produits par l'(les) auteur(s) |
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