African penguins: Grave outlook for an endangered species

Picture yourself on the western coastline of southern Africa during the Last Glacial Maximum (LGM) over 20,000 years ago, gazing upon a horizon dotted with at least fifteen large islands, the biggest spanning 300 square kilometers in area. These islands, teeming with hundreds of millions of marine birds and penguin colonies, offered ample breeding grounds for African penguins. 

As sea levels rose between 15,000 to 7,000 years ago, they gradually submerged these islands. This left only small hilltops and outcrops above water. Over the past 22,000 years, the dramatic reduction in nesting habitat has led to a tenfold decrease in the African penguin population.

Researchers in the Department of Botany and Zoology and the School for Climate Studies at Stellenbosch University (SU) have painstakingly reconstructed this paleo-historical landscape to gain insight into the vulnerability of the last remaining penguin species in Africa. 

The study, titled “A natural terminal Pleistocene decline of African penguin populations enhances their anthropogenic extinction risk,” is published in the African Journal of Marine Science.

Dr. Heath Beckett, the article’s first author and a postdoctoral fellow at SU’s School for Climate Studies, highlights the striking contrast between the paleo-historical image of thriving penguin populations and their current situation. 

In 1910, Dassen Island, a three-square-kilometer island off the West Coast, was home to an estimated 1.45 million penguins. A century later, South Africa’s African penguin population had plummeted to just 21,000 breeding pairs by 2011. They further declined to a mere 13,600 by 2019. 

Only seven breeding colonies support approximately 97 percent of the current population in South Africa today. In May 2005, the International Union for the Conservation of Nature classified the African penguin as endangered.

Penguin population sizes 20,000 years ago

To better understand the southern and western coastlines of southern Africa during the last Ice Age and the implications for penguin populations, the researchers utilized topographic maps of the ocean floor off the coast of southern Africa. 

By identifying potential historical islands situated 10 to 130 meters below present-day sea levels, the team was able to piece together the former habitats of these penguins.

To qualify as suitable nesting grounds, islands needed to offer protection from land-based predators. Foraging areas for sardine and anchovy within a 20-kilometer radius need to surround them as well. By examining these factors, scientists were able to paint a vivid picture of the once-rich habitat that sustained African penguin populations.

During the last Ice Age, with sea levels significantly lower than they are today, the southern African coast was adorned with 15 large islands. The most extensive of these islands spanned 300 square kilometers and lying 130 meters below the present-day sea surface. Over the past 15,000 to 7,000 years, as sea levels rose, 220 islands emerged. These islands would have provided suitable nesting conditions for penguins. Of these islands, 216 are less than one square kilometer in area. Some as small as 30 square meters, barely more than a rock.

Focusing on five islands off the West Coast of Southern Africa

The five largest islands off the West Coast of Southern Africa today are Robben Island (around 5 square kilometers). Dassen Island is about 3 square kilometers. Possession Island is approximately 1.8 square kilometers. Seal Island and Penguin Island are both under 1 square kilometer. Possession, Seal, and Penguin Island are situated off the coast of Namibia.

Using the earliest available population density estimates, researchers calculated potential penguin population sizes based on available island areas. They assumed the penguins usually nested no more than 500 meters from the shore. 

According to their calculations, between 6.4 million and 18.8 million individuals could have inhabited the southern Cape waters during the Last Glacial Maximum. However, due to rising sea levels between 15,000 and 7,000 years ago, the habitat for African penguins experienced a steep decline.

Dr. Beckett notes that the main goal of the research is to demonstrate the significant changes in habitat availability over the past 22,000 years. “This could have had a massive effect on penguin populations. These populations are now experiencing additional human pressures on top of this in the form of climate change, habitat destruction, and competition for food.”

Possibilities for conservation management

While these findings are troubling, the scientists argue that they also reveal the potential resilience of African penguins. Conservation and management strategies in an uncertain future could harness this fact.

“Changing sea levels would have necessitated the need for multiple relocations of breeding colonies of African penguins on timescales of centuries, if not even shorter timescales, and intense competition for breeding space as island habitat became greatly reduced in size,” said Dr. Beckett. “This historical flexibility of response provides some leeway for conservation managers to make available suitable breeding space, even in mainland sites, as long as appropriate nesting sites are made available.”

Professor Guy Midgley, interim director of SU’s School for Climate Studies and a co-author, emphasizes that this millennial-scale set of selection pressures would have favored strong colonization ability in the species: “It’s a total survivor and given half a chance, they will hang on. Island hopping saved it in the past; they know how to do this.”

However, even if relocation opportunities are provided, many questions remain. How much more will it take for these penguins to persist in the face of modern human pressures? Competing against the commercial fishing industry and humanity in general for the same food sources puts penguins – and other marine life – at a significant disadvantage. 

The researchers caution that “for any relocation measures to be successful, sufficient access to marine food resources remain a vital element of a coordinated response to prevent extinction of the species.”

This research sheds light on the African penguin’s historical decline and emphasizes the need for continued conservation efforts. Understanding the past is a crucial step in safeguarding the future of the last remaining penguin species in Africa.

More about African penguins

African penguins (Spheniscus demersus), known for their donkey-like braying call, are the sole penguin species present on the African continent. They inhabit the waters and islands off the southwestern coast of Africa. More specifically, along the coasts of South Africa and Namibia. Here are some more interesting facts about African penguins:

Physical characteristics

African penguins are medium-sized. They stand at about 60-70 cm (24-28 inches) tall and weighing between 2-5 kg (4-11 lbs). They have a distinctive black and white coloration with a black stripe across the chest. Another distinguishing characteristic is a black upside-down U-shaped pattern on the front. Their faces feature a black mask with white markings around the eyes.

Diet

They mainly feed on small fish, such as sardines and anchovies, but also consume squid and crustaceans. African penguins are excellent swimmers. They can dive to depths of up to 130 meters (426 feet) to catch their prey.

Breeding

African penguins are monogamous and usually mate for life. They nest in burrows, which they either dig themselves or find in guano deposits on rocky islands. The female typically lays two eggs, and both parents take turns incubating the eggs for about 40 days. After hatching, the chicks are cared for by their parents for several weeks. They are then left to join a crèche (group of chicks) while the parents forage for food.

Lifespan and threats

African penguins have a lifespan of around 10-15 years in the wild. They face numerous threats, including habitat destruction, oil spills, climate change, and overfishing, which reduces their food supply. As a result, their population has drastically declined, leading to their classification as an endangered species.

Conservation efforts

To protect and conserve African penguins, numerous organizations and initiatives are in place. These include monitoring and managing breeding colonies, rehabilitating oiled and injured penguins, establishing marine protected areas, and working with the fishing industry to reduce competition for food resources.

Understanding and appreciating these unique birds is crucial for raising awareness and promoting their conservation to ensure the survival of the African penguin species.

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