Image Source: Flickr. By: Paul Mannix
The African penguin (more commonly known as the Jackass penguin) is found on over 20 small islands and mainland areas along the south-west and south coast of Africa. They are currently listed as ‘Endangered’ on the IUCN Red List, which is attributed to a combination of factors. Some of the more well- known factors include oil spills, egg harvesting by humans and disturbance to nesting sites. Recently, the effects of global warming are also indirectly creating detrimental affects on the remaining number of African penguins found along the western coast of South Africa. Indirect effects of global warming include a decline in the amount of food sources as well as a change in the availability of food sources for the penguins.
Large-scale commercial fisheries (such as purse-seine trawling as well as climate change impacts on water temperatures) have caused shifts in the type and amount of prey available to the penguins in their feeding range. Roy et al. (2007) noticed that both anchovies and sardines, the two main prey items for African penguins, have shifted more eastward of South Africa due to the changes in water temperature. A study done by Crawford et al. (2011) investigated how the distribution shift of anchovies and sardines will impact on the African penguin population numbers in South Africa.
African penguin distribution map: The number of breeding penguins in South Africa has declined from about 56 000 pairs in 2001 to 21000 pairs in 2009, while the global population is recorded as 26 000 pairs in 2009.
During breeding, African penguins need to search for food within 40 km of their breeding or nesting site. The further that a penguin travels searching for food, the more energy it expends, which ultimately means less food for the chicks. In addition, adults also face a food shortage which leads to a deterioration in their health. Therefore, the feeding conditions before breeding influence breeding success as well as the decision to participate in breeding.
Crawford et al. (2011) found that due to the eastward shift in sardines and anchovies as well as the overall decline in these prey species; that the number of penguin nests and breeding pairs has declined exponentially. They found that the biomass of these prey species and number of penguin nests were highly correlated.
They also found that the local availability of these prey species to the penguin breeding sites is also a highly important factor influencing the African penguin numbers. They inferred this by the observation that the abundance of anchovy was still very high, although the anchovy distribution shifted further away from the penguin breeding sites.
African penguin feeding
Besides the obvious importance of this study in bringing to our attention the massive decline in African penguin numbers over the years, it also emphasizes to us the need for better fisheries management. We need to consider not only the overall abundance of prey but also the local availability of the prey species.
An important follow up study to this one, as suggested by Crawford et al. (2011) would be to investigate the influence of fishing on the availability of food to the African penguins and then further determine how this can possibly be managed. Another very important factor to consider is that the distribution shift of these prey species not only affects African penguins, but also other animals such as the Cape gannet and Cape cormorants. Since the change in shift of these fish prey species, Cape gannet breeding success has declined rapidly as well, inadvertently impacting on the gannet population.
African penguin with chick
This article demonstrates to us just how fragile our planet really is. Everything operates in an almost balanced scale whereby the global change drivers created by humans, can easily and noticeably tip this balanced scale quite easily without us even noticing. Only until a species such as the iconic and adorable Jackass penguin starts to disappear do people begin to take notice and action to avoid their possible extinction.
This paper is worth a read and provides a good synthesis of information to the changes that the African penguins have undergone since the late 1990s.
Crawford, R. J. M., Altwegg, R., Barham, B. J., Barham, P.J., Durant, J.M., Dyer, B.M., Geldenhuys, D., Makhado, A. B. Pichegru, L., Ryan, P.G., Underhill, L.G., Upfold, L., Visagie, J., Waller, L.J., Whittington, P.A. 2011. Collapse of South Africa’s penguins in the early 21st century. African Journal of Marine Science 33(1): 139-156.