Winter is well and truly underway with storm fronts hauling around the Cape, and the African penguin’s breeding season is in full swing. The researchers on the island have been making use of their rain coats and water proof gear. Despite the occasional bout of bad weather, 38 deployments have been carried out so far and data collection is almost complete.
But Robben Island is not the only place where African penguin foraging behaviour is monitored at sea using GPS loggers. Deployments are also carried out at all other important penguin breeding sites including Dassen Island, St Croix and Bird Island. Amongst other things, the tracking data are used as part of an ongoing study to investigate the effects of fishing closures around penguin colonies. The study aims to assess whether preventing fishing in waters in close proximity to the main colonies can impact penguin breeding success and foraging behaviour, by reducing the penguins’ competition with fishermen for food. The project has been running since 2008, and if results can show that disallowing fishing has a positive impact on the penguin population, No-take zones may be implemented around the island colonies.
Map showing some of the main African penguin breeding colonies, taken from Sherley et al. 2014.
In parallel with tracking the movements of penguins at sea using GPS loggers, foraging trip duration is also being measured at Robben Island by monitoring the penguins at the nest. At a number of nests, camera traps have been placed at the nest entrance, in order to capture when the penguins depart to forage, then at what time they return to feed their chicks. This information can then be used to determine the duration of the bird’s absence of the nest as a proxy for foraging trip length. When the chicks are small, one parent stays at the nest to keep the chicks warm, and to guard them from predators. However, once the chicks are old enough to thermoregulate themselves, both parents will go out to sea in order to provide enough food to satisfy their chicks increasing energy demand. At some nests, cameras are being used in combination with data-logging scales, which are able to record the weight of any penguin that stands on or walks over them. The information on the penguin’s weight can then be used to determine weight gain over the foraging trip, and to estimate the body condition of adult penguins. This method of collecting data is minimally invasive, measures were taken to minimise the stress of handling.
A camera trap image showing a penguin departing the nest.
This year’s tracking could not have been realized with the kind support, boundless help and effort of the Earthwatch team and the Robben Island Museum. Our special thanks however go to Mpumi, Phakamile Zungu, Davide Gaglio, Nola Parsons, Kerrie-Lee Dobbie, Sally Hofmeyr, Barbara Barham, Kate Robinson, Antje Steinfurth and Richard Sherley for their hard work and endeavors, companionship and invaluable assistance in the field.
For now the GPS logger deployments at Robben Island have finished for the season, but the penguins keep on swimming!
Sherley RB, Waller LJ, Strauss V, Geldenhuys D, Underhill LG, et al. (2014) Hand-Rearing, Release and Survival African Penguin of Chicks Abandoned Before Independence by Moulting Parents. PLoS ONE 9(10): e110794. doi:10.1371/journal.pone.0110794