Abstract
BackgroundThe 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.MethodsOver 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.ResultsWhile 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.ConclusionsThe 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.
Highlights
The early life of marine apex predators is poorly known, for diving species
First juvenile movements: a seasonal migration? Net Square Displacement (NSD) time series analysis showed that juvenile movement patterns could be divided into three distinct phases: (1) a first initial dispersion, with juveniles predominately moving southwest and south-east of the Crozet islands within the vicinity of Antarctic Polar Front (APF); (2) a departure from these summer feeding grounds continuing in a south-west direction; (3) a exploration phase during winter, when juveniles range over a large area (Fig. 3b), with variable environmental conditions (Additional file 1: Figure S6)
We suggest that there are three possible, non-exclusive explanations: 1) juveniles rely on environmental cues to find profitable foraging areas, 2) they follow adult conspecifics, especially during their initial dispersion towards the APF and/or 3) their general movement pattern, at least in part, is inherited
Summary
The early life of marine apex predators is poorly known, for diving species. The period following emancipation of juveniles from their parents is critical [1]. During their first years, juveniles have, in general, a lower survival rate than adults [2]. Many studies have shown that in long-lived species the foraging skills of juveniles are less proficient than those of adults [3]. Such differences are mostly related to physiological and developmental constraints [4], and the time needed to obtain sufficient knowledge about food acquisition and the environment to improve foraging skills [5]. The improvement of skills is strongly dependent on the particular environment encountered and various temporal and/or spatial scales [6]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
