INBREEDING ADDS TO GROWING THREATS TO AFRICA’S SMALLEST WILDCAT, STUDY FINDS

Populations of the black-footed cat, a lesser-known feline native to Southern Africa, have been declining for the past half a million years and exhibit high levels of inbreeding. This could heighten their risk for amyloidosis, a disease highlighted in a new genetic study.

“Genomic studies often focus on large, charismatic cats, leaving smaller species like the black-footed cat overlooked,” says Andrew Kitchener, principal curator of vertebrates at National Museums Scotland and author of the study. “However, every species has its own fascinating story, and the black-footed cat is no exception.”

Weighing about as much as a large pineapple, the black-footed cat (Felis nigripes) is one of Africa’s smallest and rarest felines, known for its endearing qualities. It inhabits arid steppe and grassland savannas in Southern Africa, including Namibia, South Africa, and Botswana, and is classified as vulnerable to extinction by the IUCN Red List.

Like many threatened species, the black-footed cat faces pressures from habitat loss, degradation, and climate change. Additionally, about 70% of captive black-footed cats succumb to amyloidosis, a fatal disease linked to harmful genetic mutations, believed to be hereditary. Wild populations are also at risk, though determining the mortality rate is challenging.

Over the past few decades, significant insights into the cat’s conservation needs have emerged from long-term field studies in South Africa and Namibia. Black-footed cats are agile nocturnal hunters, with striking tawny coats adorned with black spots and stripes, resembling domestic cats. They consume about a fifth of their body weight in prey each night, showcasing their voracious appetites. However, mortality rates are high, with nearly 40% of studied populations perishing each year, primarily due to predation and disease, according to Alexander Sliwa, project leader for the Black-footed Cat Working Group and curator at Cologne Zoo. Until now, genetic research on this species has been limited.

To address the gap in research, Kitchener and his colleagues began by generating the black-footed cat genome from several reference samples. They combined this data with previously published genomic information for the species and compared it to the genomes of other small cat species.

The study reveals that the black-footed cat diverged from the Felis genus approximately 3 million years ago, making it one of the oldest small cat species. There is also evidence of hybridization with ancestors of the jungle cat (Felis chaus), sand cat (Felis margarita), and wildcat (Felis silvestris). The researchers identified genes that contribute to the black-footed cat’s success as a hunter, including those linked to tracking fast-moving objects, acute hearing, and a high metabolic rate that allows them to remain active on cooler nights.

However, the analysis also indicates a troubling decline in the black-footed cat population over the past half-million years. The researchers found significant inbreeding, with some measures showing even lower genetic diversity than certain large cats like lions (Panthera leo) and jaguars (P. onca). This high level of inbreeding is likely a result of historical and ongoing habitat fragmentation, which may increase the risk of amyloidosis, a disease with a genetic basis.

Sliwa, who was not involved in the study, noted that it fills a critical gap in genetic research on small cats and suggested that future studies could benefit from larger sample sizes and broader geographic coverage.

Currently, black-footed cat populations face numerous threats, including land-use changes, habitat fragmentation, climate change, and disease. In Sliwa’s long-term study sites in South Africa and Namibia, the impacts are concerning.

“I’m witnessing a total collapse of the population in my study areas,” he reports.

In 2023 and 2024, Namibia experienced its worst drought in a century, exacerbated by El Niño and climate change. Projections indicate that such droughts are likely to become more frequent and severe over the next century.

Sliwa highlighted that his study area in southern Namibia has seen virtually no rainfall in the past two years. This region has historically been near the limits of what the black-footed cat can tolerate in terms of aridity. The ongoing drought is pushing these cats out of their preferred short-grass habitats and into riverbeds, bringing them into closer contact with farmers and their dogs. The combined threats of starvation and dog attacks led to the deaths of all the study animals last year.

The black-footed cat’s environment is also changing in other ways. Human activities are driving many large carnivores toward extinction, resulting in the decline or disappearance of lion, leopard (Panthera pardus), and cheetah (Acinonyx jubatus) populations across much of the black-footed cat’s range. In Sliwa’s study areas, medium-sized predators like caracals (Caracal caracal) and black-backed jackals (Lupulella mesomelas) have taken their place, both of which pose a threat to black-footed cats.

“We’re dealing with two very generalized predators versus one highly specialized one,” Sliwa explains. “Caracals and black-backed jackals are the main predators of black-footed cats, leading to at least a 30% loss of the population due to predation.”

Sliwa has observed the effects of amyloidosis on the wild black-footed cat population, but he notes that determining the extent of mortality caused by the disease is challenging.

Amyloidosis involves the deposition of abnormal proteins in organs or tissues. In wild black-footed cats, excessive thirst is often the first sign of the illness. Typically, these cats obtain all the hydration they need from the blood of their prey. However, as the disease impacts their kidneys, affected cats begin to seek out standing water. Once they do, they usually succumb to the disease within a month, either dying directly from it or becoming disoriented and more vulnerable to predators, according to Sliwa.

“It’s difficult for us to differentiate,” Sliwa explains. “Was that purely a case of predation because the animal wasn’t alert, or was it already sick and then taken by a predator?”

This combination of threats can lead to the disappearance of entire populations, an outcome that Sliwa and his colleagues are working tirelessly to prevent.

For the black-footed cat and other endangered species, understanding genetic susceptibility to diseases is crucial, Sliwa emphasizes, but it’s not sufficient on its own for conserving wild populations. Effective conservation requires field data and adequate funding to support on-the-ground efforts.