Abstract

Tracking studies of juveniles are rare compared to those of adults, and consequently little is known about the influence of intrinsic and extrinsic factors on activity during this critical life stage. We used hourly GPS data, collected from 66 Antarctic fur seal pups from birth until moulting, to investigate the explanatory power of multiple individual-based and environmental variables on activity levels. Pups were sampled from two nearby breeding colonies of contrasting density during two subsequent years, and a two-state hidden Markov model was used to identify modalities in their movement behaviour, specifically ‘active’ and ‘inactive’ states. We found that movement was typified by central place exploration, with active movement away from and subsequent return to a location of inactivity. The probability of such directed exploration was unaffected by several factors known to influence marine mammal movement including sex, body condition, and temperature. Compared to pups born at the high-density colony, pups at low-density were more active, increased their activity with age, and transitioned earlier into the tussock grass, which offers protection from predators and extreme weather. Our study illustrates the importance of extrinsic factors, such as colony of birth, to early-life activity patterns and highlights the adaptive potential of movement.

Highlights

  • Tracking studies of juveniles are rare compared to those of adults, and little is known about the influence of intrinsic and extrinsic factors on activity during this critical life stage

  • GPS data were successfully collected from a total of 66 Antarctic fur seal pups from two nearby breeding colonies of contrasting density (Fig. 2a)

  • We collected and analysed hourly GPS data from Antarctic fur seal pups tracked from birth until moulting in order to investigate the drivers of movement patterns and activity levels during this critical life stage

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Summary

Introduction

Tracking studies of juveniles are rare compared to those of adults, and little is known about the influence of intrinsic and extrinsic factors on activity during this critical life stage. Marine vertebrates in particular have benefited from such improved methodologies, exemplified by a recent analysis of more than 2600 tracked individuals documenting extraordinary convergence in movement patterns across 50 ­species[6] Despite these recent advancements in marine tracking research, several authors have drawn attention to age and sex biases in the literature, with datasets of adult females being over-represented[3,7]. This focus on adults is problematic because the movement and distribution of neonatal and juvenile individuals is of key importance for understanding population dynamics. Suggest that habitat choice as adults may be primarily driven by intrinsic factors early in life rather than size-related differences as adults

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