Measuring an African penguin chick on Robben Island
|This research forms part of an interdisciplinary, multi-organisation initiative to build a better understanding of the changing ecology of the Benguela upwelling ecosystem and develop an ecosystem approaches to fisheries in South Africa.
The African penguin is endemic to southern Africa and the present population is estimated to be about 2% of what it was 80 years ago as a result of prolonged human activity in the region. In South Africa, estimates of the number of African penguins breeding decreased from 56 000 pairs in 2001 to 19 000 pairs in 2015. The species is currently listed as endangered on the IUCN Red List.
Robben Island hosts the longest running, uninterrupted time-series on the population dynamics and behaviour of the species. Through a collaboration between the Department of Environmental Affairs (DEA), the University of Cape Town, the University of Bristol, the University of Exeter and Robben Island Museum, the numbers breeding and breeding success of African penguins has been monitored on the island since 1989.
Since 2001 (the year following the Treasure oil spill), a sample of around 200 nests has been followed intensively as part of an Earthwatch project, on which I am Lead Scientist. Nests are checked
Foraging tracks of three breeding African penguins
monitored by GPS logger deployment.
Monitoring an African penguin nest
on Robben Island.
|approximately every 10 days and the contents and presence of adults recorded. The project also monitors individually marked birds to obtain data on survival rates, longevity and lifetime reproductive success; conducts counts of penguins moulting along the shoreline (data which forms the basis of assessments for the IUCN) and assists with the annual census of breeding pairs. From the beginning of the 2008 breeding season, the monitoring being carried out was part of a DEA led-project investigating the efficacy of closing areas around seabird colonies to fishing as a conservation tool. As penguins are thought to be restricted to foraging within 20 km of their breeding colony while feeding chicks, it is hoped that such closures will benefit breeding birds by increasing the prey available to them during the crucial chick rearing stage (see here).
During the winters of 2008 and 2009, an area around Dassen Island (30 km north of Robben Island) was closed to fishing, while a similar area around Robben Island was open. From 2011 to 2013, the situation was reversed. By comparing the penguin populations at these two colonies, and monitoring any differences in the birds’ ability to supply food to their chicks in the closed and open areas, we can obtain crucial information to guide future legislation on fisheries management, such as spatially enforced fishing quotas or the development of Marine Protected Areas. In each year a sample of chicks are weighed and have their head and/or flippers measured. These data are used to generate an index of body condition and to compare growth rates over time between closed and open colonies to assess if and how fishing impacts on the productivity of African penguins.
In addition, to understand how changing fish stocks affect the penguins, it is necessary to know where they go to find the fish, how long it takes them to find the fish and then how much time it takes them to catch enough prey to feed both themselves and their chicks. Penguins from Robben Island are selected to be fitted with small, lightweight GPS and time-depth data-loggers. These are attached to penguins using tape to temporarily affix the loggers to the bird’s feathers. Once the logger is fitted the birds will be tracked as they perform one foraging trip (see image, left). When the bird returns, the data are downloaded from the loggers and the data are analysed using GIS software. Between 2011 and 2013 this work was the focus of my PhD student Kate Campbell (née Robinson). You can learn more about her tracking work on her research blog.
The data obtained from Robben Island are used in reports to DEA and other working bodies responsible for overseeing pelagic fisheries in South Africa. In addition, the results of the breeding success studies and survival estimates have been summarised in five recent publications.