Caracal, meet penguin: How humans pushed unlikely predator and ...

CAPE TOWN — The sharp pop of an air gun echoes through the forested flanks of Constantia as volunteers herd a raiding troop of baboons away from the affluent Cape Town suburb that blossomed in their historic stomping grounds. The Cape baboons (Papio ursinus) play an important ecological role, but with easy access to calorie-rich human food and no natural predators left, the population ballooned. It now clashes regularly with the city’s frustrated human residents.

The city is part of a “complex” system, says Gabriella Leighton, a postdoctoral researcher at the University of Cape Town,. Almost 5 million people live here, but South Africa’s second most populous city is also part of the Cape Floral Kingdom, a global biodiversity hotspot. As the impacts of centuries of human-induced change ricochet through the system, altercations are unavoidable.

But Leighton, an expert in urban ecology and carnivore conservation, also describes the Cape Peninsula — a rugged, nearly 500-square-kilometer (190-square-mile) area of exceptional biodiversity that encompasses the city and suburbs — as a natural laboratory. Recently, she published the first record of wildcats regularly hunting marine prey. A group of local caracals (Caracal caracal), medium-sized wildcats distinguished by their sharply pointed, lavishly tufted ears, are hunting seabirds, including endangered Cape cormorants (Phalacrocorax capensis) and African penguins (Spheniscus demersus).

The highly opportunistic hunter’s dietary shift is likely the result of large-scale, human-induced changes that have led to more caracal-seabird encounters over time, Leighton says. The complex cascade of changes started a long time ago, escalating with the arrival of European settlers.

The caracal is a medium-sized wild cat distinguished by their sharply pointed, tufted ears. Image by Fenton Cotterill. Cape Town is part of a complex system that includes millions of people living in a global biodiversity hotspot Image by Petro Kotze. The history of the Cape Peninsula’s caracals

Before European settlers arrived, the Cape Peninsula was rife with wildlife. Large antelope were aplenty, and elephants (Loxodonta africana), black rhinos (Diceros bicornis), lions (Panthera leo), leopards (Panthera pardus) and caracals were widespread.

Jan van Riebeek, the founder of the Dutch Cape Colony, shot his first hippo (Hippopotamus amphibius) 12 days after arriving at the cape in 1652, tolling the death knell for the great nomadic herds of wildlife here.

The change was swift and extensive. By the 1700s, the hippos were exterminated from the Cape Peninsula, and lions, leopards and most large mammals followed. Some, like the quagga (Equus quagga quagga), a zebra subspecies, and the blue antelope (Hippotragus leucophaeus), were wiped out forever.

The settlers also chopped down local trees for construction and other domestic needs and planted imported species for fruit, fuel and shade.

“It’s a fascinating place,” says Deborah Winterton, the regional science liaison officer for South African National Parks (SANParks), the management authority of the city’s iconic Table Mountain National Park (TMNP). However, she points out that it’s also a broken system, where nature is out of balance.

Urban sprawl has turned the Cape Peninsula into an ecological island surrounded by city and sea; the peninsula today is a fragmented landscape managed by multiple independent authorities and property owners.

Caracals can shift their diet according to where they are, and their most common prey is birds and rodents. Image © Urban Caracal Project. The Cape Point section of the Table Mountain National Park in South Africa, a coastal section of South Africa that could not escape the impacts of human-induced change. Image by Petro Kotze.

In this rapidly changing environment, a species’ survival depends partly on dietary flexibility. The caracal emerged as king in this regard. The cat became the region’s de facto top predator after lions and leopards disappeared. Leighton says the highly generalist species shifts its diet according to its surroundings; researchers have recorded more than 70 species that make up the caracal’s diet. Birds and rodents are the most common prey, but it also quietly stalks hares, hyraxes, small monkeys, reptiles and even insects.

Caracals are attracted to areas where the hunting is likely better, Leighton says. In the south of the peninsula, this is along the coast. Stable isotope analysis of caracals’ fur indicates that about 25 cats are now regular coastal foragers. They hunt on the beach and rocky shores and in seabird colonies along cliffs, mostly in the Cape Point section of TMNP. Seabirds including cormorants, penguins, gulls, gannets and terns, routinely comprise about a third of their diet.

However, even some of the prey is new to the area.

Though they probably spent time on the mainland, African penguins only recently settled to breed in the southern peninsula. A pair arrived in the 1980s at Boulders Beach, on the eastern side of the peninsula, and blossomed into a colony.

“We don’t really know why the penguins came to Boulders,” says Christina Hagen, a penguin conservation biologist at BirdLife South Africa. African penguins are endemic to small islands off the coasts of South Africa and Namibia, and it’s possible the Boulders pair made the move to the mainland because of a shortage of food around their birth colony, or else they were pushed out due to overcrowding, Hagen says. They likely chose Boulders, she adds, because cormorants and other seabirds were roosting in the area, suggesting it was suitable.

Others have postulated that the number of mainland seabird colonies along the coast has increased as people destroyed offshore seabird colonies’ habitats. In contrast, protection of the coast around Cape Town has improved.

However, the contraction of habitat also pushes the birds into the territory of native terrestrial predators, like the caracal.

Centuries after European settlers first arrived in the Cape, the caracal is the largest remaining predator. Image by Hilton Davis. The Boulders penguin colony in Cape Town, South Africa, where the endangered birds settled in the eighties. Image by Petro Kotze. A butterfly effect of changes

But even for the caracals, Leighton says, there’s a hidden cost to these high-nutrient prey. Seabirds that feed far offshore are exposed to marine pollutants. Leighton says the caracals that feed on seabirds are more exposed to persistent organic pollutants and metal contaminants, such as arsenic, mercury and selenium.

“Most caracals are exposed to various pollutants, and we are unsure how these all interact to exert physiological costs on the animals,” she says.

While it’s hard to study the impact of pollutants in wild populations, studies of captive animals have shown the effects can be very detrimental.

“Our work suggests that there are physiological costs, which suggests that this exposure may impact their biological fitness and eventually have population-level impacts,” Leighton says.

This adds to the gauntlet of threats caracals already have to navigate in an urban environment. Caracals are regularly hit by cars, poisoned, attacked by domestic dogs, and caught in wire snares set for game animals.

This young caracal died due to exposure to rat poisons, one of the multiple challenges that caracals face in their urban environment. Image by Urban Caracal project. A caracal captured in Cape Point. A group of cats are regularly hunting marine resources in this coastal stretch of South Africa. Image by Luke Nelson.

Leighton says the Cape Peninsula’s caracal population has lower genetic diversity due to its isolation from other cats. Inbreeding and low genetic diversity can further affect their health and might lower their resistance to the negative effects of diseases and pollutants.

Regardless, when two caracals killed nearly 130 penguins over two months at Boulders Beach in 2016, officials stepped in and relocated the cats, even though local caracal conservationists staunchly oppose relocation. While the peninsula colonies of African penguins and Cape cormorants are a relatively small percentage of the global population, they’re dwindling at an alarming rate. Both are categorized as endangered on the IUCN Red List.

Yet for Leighton, the discovery that caracals have a habit of eating seabirds is cause not for concern but for celebration. Regardless of the changes and challenges, they should be seen to highlight the abundance of ecology that can still be conserved in urban areas.

Banner image: African penguins are now an Endangered species and listed as in need of urgent conservation action. Image by Petro Kotze.

Citations:

Showers, K. B. (2010). Prehistory of Southern African forestry: From vegetable garden to tree plantation. Environment and History, 16(3), 295-322. doi 10.3197/096734010X51977

Boshoff, A., & Kerley, L. (2001). Potential distributions of the medium- to large-sized mammals in the cape floristic region, based on historical accounts and habitat requirements. African Zoology, 36(2), 245-273. doi:10.1080/15627020.2001.11657142

Winterton, D. J., van Wilgen, N. J., & Venter, J. A. (2020). Investigating the effects of management practice on mammalian co-occurrence along the West Coast of South Africa. PeerJ, 8, e8184. doi:10.7717/peerj.8184

Leighton, G. R. M., Froneman, P. W., Serieys, L. E. K., & Bishop, J. M. (2024). Sustained use of marine subsidies promotes niche expansion in a wild felid. Science of The Total Environment, 914, 169912. doi:10.1016/j.scitotenv.2024.169912