The period of emancipation, when juvenile seabirds change from a terrestrial existence to a life at sea, is associated with many challenges. Apart from finding favourable foraging sites, they have to develop effective prey search patterns and physiological capacities that enable them to capture sufficient prey to meet their energetic needs. Animals that dive to forage, like king penguins (Aptenodytes patagonicus), need to acquire an adequate breath-hold capacity, allowing them to locate and capture prey at depth. To investigate the ontogeny of their dive capacity and foraging performance, we implanted juvenile king penguins before their first departure to sea and also adult breeders with a data-logger recording pressure and temperature. We found that juvenile king penguins possessed a remarkable dive capacity when leaving their natal colony, enabling them to conduct dives in access of 100 m within their first week at sea. Despite this, juvenile dive/foraging performance, investigated in relation to dive depth, remained below the adult level throughout their first year at sea, likely reflecting physiological limitations due to incomplete maturation. A significantly shallower foraging depth of juveniles, particularly during their first five months at sea, could also indicate differences in foraging strategy and targeted prey. The initially greater wiggle rate suggests that juveniles fed opportunistically and also targeted different prey than adults and/or that many wiggles of juveniles reflect unsuccessful prey-capture attempts, indicating a lower foraging proficiency. After five months, this difference disappeared, suggesting sufficient physical maturation and improvement of juvenile foraging skills.
HIGH RESOLUTION ECG AND DEPTH DATA LOGGER - A Novel Device to Study Breath Hold Diving Induced Variations of the PQ Interval
