- Small wildcat species suffer from habitat loss, hunting and human conflicts, just like better-known big cats. But some small wildcat populations also face threats from other felines: hybridization.
- Interbreeding with domestic cats (Felis catus), and also with other wildcat species, can alter the outward appearance, behaviors and genetic profiles of wildcats, and create conservation dilemmas about how best to define and protect a species.
- In Scotland, hybridization caused the functional extinction of a subpopulation of European wildcat (Felis silvestris), but scientists and conservationists are collaborating to rebuild the genetically distinct wild population with kittens reared from selectively bred wildcats.
- To protect the African wildcat (Felis lybica) in South Africa, international partners are working to reduce interbreeding by sterilizing domestic and feral cats near the borders of Kruger National Park. Hybridization can also occur between wildcat species and raises questions about preserving genetic purity vs. ecosystem function.
Charismatic big cats (think tigers and leopards) get the lion’s share of conservation attention, while their close relatives — 33 species of small wildcats roaming five continents — get far less notice. Yet they too often urgently need protection.
Like their larger counterparts, these felids suffer from habitat loss, hunting and human conflicts. But some face a less-known feline threat: hybridization with Felis catus, the domestic cat — darling to cat lovers the world over and YouTube superstars.
In Europe and South Africa, interbreeding by small wildcats with housecats or feral domestic cats has altered the genetic makeup of wild species and created conservation dilemmas.
To preserve the genetic integrity of these wildcats, conservationists plan to boost dwindling populations with wild-bred kittens, ramp up sterilization of feral domestic cats, and find better ways to study these elusive wild felids.
Doing so is important not only for individual species, but for protecting ecosystems from instability. “Small wildcats are habitat specialists and their losses can have wide impacts,” says Wai-Ming Wong, director of NGO Panthera’s small cats program. “Given the current biodiversity crisis, it’s really important to maintain ecosystem balance.”
Hybrids have always posed a conundrum for conservationists. Admixing “domestic” genes with the DNA of wild species through crossbreeding — a process known as introgression — can increase genetic diversity and even improve a species’ ability to prevail in a changing landscape. But the distinct genetic heritage of wild species can be lost via intermating.
Wild-domestic hybrid cats, for example, may display different behaviors from those in the wild, alter their use of habitat, or be more susceptible to disease. These crossbred cats also might not meet the specific genetic and taxonomic criteria that form the basis of legal protections for wildcats.
Holding onto Scotland’s Highland tiger (Felis sylvestris)
“Hybridization is a tricky issue,” says Helen Senn, head of conservation at the Royal Zoological Society of Scotland (RZSS) in Edinburgh and project lead for Saving Wildcats, an NGO. That’s especially the case for a subpopulation of European wildcat (Felis sylvestris) that once roamed Scotland, but which has been hit hard by wild-domestic hybridization.
Today, studies show that few of Scotland’s remaining wildcats (outside of zoos) display enough of the distinct genetic markers and physical traits to be defined as the “Highland tiger.” Although domestic cats were likely introduced to the United Kingdom in Roman times, whole genome studies point toward hybridization as “a recent phenomenon that probably only happened within the last 60 or so years,” Senn says.
That’s an important point for conservationists because “that tells us something changed to create a breakdown between these two species,” she explains. As habitat loss and persecution of Scotland’s wildcats escalated in recent decades, the dwindling population of Felis sylvestris likely mated with the more available domestic cat, Felis catus.
“Then things rapidly descended into what we call a ‘hybrid swarm,’” says Senn. “Which just means that everything is very mixed up [genetically].” In other European countries, analyses find that interbreeding with domestic felines affects anywhere from 3-21% of wildcat populations. But in Scotland, all of the wild-living cats in study samples show evidence of hybridization.
Today, Senn leads a European partnership tasked with rebuilding Scotland’s wildcat population. The collaborators plan to reintroduce wildcats into remote areas where the organization can still monitor the more isolated cats’ welfare.
Over the next three years, conservationists plan on annually releasing about 20 kittens from breeding pairs of captive (zoo) and wild-caught felines that scored at least 75% on a combination of specific wildcat genetic markers and pelage characteristics.
“The genetics are very important to helping us resolve taxonomy and understand what we’re trying to conserve,” said Senn, a conservation genetics specialist whose work ranges from the reintroduction of pond mud snails in Scotland to the scimitar-horned oryx in Chad.
Earlier this year, the first cohort of young wildcat kittens were old enough to move into individual enclosures at the Highland Wildlife Park, where they can continue to mature and work on their survival skills. They should be ready to release by the middle of the year.
After release, the young cats will be tracked using GPS collars and camera traps. Senn also wants to monitor the genetics of subsequent generations through fecal samples, hair traps and camera images. The scientist will also be comparing the DNA profiles of the wildcats with samples from the feral domestic felines that roam the same general area.
Studies on the rebound of the European wildcats in the Swiss Alps have modeled the size of wildcat populations needed to preserve the species’ genetic legacy, but Senn doesn’t know exactly how many cats need to be reintroduced to keep the Scottish wildcat from being overwhelmed by domestic cat DNA.
“We want to see a population of wildcats which are basically fit, with healthy numbers, that are reproducing with each other, and not breeding with domestic cats,” she says. “If we can do that, then we are onto a winner.”
Saving the African wildcat in South Africa
Hybridization is also a concern in South Africa, where the dust-colored, long-legged African wildcat (Felis lybica) roams. Although a 2016 IUCN survey found that F. lybica interbreeding with domestic cats has been fairly low across Africa’s broader landscape, the threat to the wildcat tends to be highest in parts of South Africa where human populations (and domestic cat numbers) are highest — especially near the borders of national parks.
One key recommendation coming out of the IUCN survey is to actively neuter domestic cats in these border areas to create buffer zones that reduce crossbreeding, says Louise Holton, president of Alley Cat Rescue (ACR), a U.S.-based nonprofit. Local veterinarians were already taking this approach, but ACR funding has helped ramp up trap-neuter-return (TNR) capacity around Kruger National Park. This approach takes care to return sterilized cats to the areas where they were found so that established cat populations are maintained, and there’s no “vacancy” created for an influx of new cats.
“The [feral cat] problem is enormous and ACR was able to help [veterinarians] scale up,” says Holton, who is originally from South Africa.
More than 5,000 feral and stray domestic cats have been sterilized and vaccinated against rabies since 2019, at a cost of around $45 per cat. The project has expanded its capacity to include three additional organizations, but Holton estimates there are still at least 3,500 unneutered cats around Kruger National Park, and thousands more near other parks. She especially wants to get blood samples for genetic analysis from hybrid-looking cats undergoing sterilization to get more DNA data on hybridization.
Holton notes that African wildcats and brown domestic tabbies share some similarities, but the wildcats have long front legs and an orange tinge to the ears, while hybrids have lost the long front legs and always have white spots somewhere — small but important visual distinctions when trying to identify and maintain the integrity of a wild species.
In addition to fieldwork, Holton is working rigorously to obtain more funding to keep these projects going. “African wildcats are amazing creatures,” she says. “And that’s where our beloved domestic cats started 10,000 years ago. Why not use a sterilization program that will stop the hybridization, yet keep the [wildcat] population doing what they should do?”
Reducing human-wildcat conflicts
Domestic cats aren’t the only threat to the pure genetic lineages of various small wildcat species. In southern Brazil, for example, researchers found at least 40% hybridization between two wild species, Geoffroy’s cat (Leopardus geoffroyi) and the southern tiger cat (Leopardus guttulus), when they analyzed DNA samples in Rio Grande do Sul state.
The main “hybrid zone” was at the southern extent of the much-fragmented, very ecologically stressed Atlantic Forest and the northern extent of pampas grassland where the two wildcats’ ranges overlap.
The hybrids aren’t easy to distinguish by looks alone: purebred Geoffroy’s cats are generally more robust and spotted with non-remarkable tails; southern tiger cats are typically lithe with long tails, stripes or open spots, and larger ears.
But looks aren’t the key issue, says Jim Sanderson, founder and director of the nonprofit Small Wild Cat Conservation Foundation (SWCCF) and an IUCN small cat specialist. “I think it’s more important to [maintain a specific] ecological role in nature than to be fixated on hybrid [looks],” Sanderson says. “Functional extinction is a terrible loss. So I’d rather have a weird-looking cat than no cat at all.”
In the increasingly human-dominated landscapes where he works, Sanderson focuses on finding ways to mitigate the conflicts with people that get wildcats killed. In Chile, for example, the diminutive güiña (Leopardus guigna) often preys on chickens raised by local farmers. The Pampas cat (Leopardus colocolo) has a similar penchant.
Fewer felines suffer from retaliatory killings when henhouses are repaired and cat-fortified, or when people are supplied with tailless chickens that are harder for wildcats to catch.
Other practical conservation approaches include equipping rural herders with guard dogs to stop wildcat-associated predation of alpacas, llamas and goats. Protecting bigger cats, such as mountain lions, can also help the small cats because the big cats can reduce populations of feral dogs that threaten smaller felids. “I just want to keep cats in the game,” says Sanderson.
Small wildcat future
A major hurdle to understanding the impacts of hybrids on the ecological roles played by small wildcats is the lack of studies to determine what these species need to thrive. That’s partly because small cats are incredibly elusive, with many conservationists having rarely — if ever — seen the cats they’re trying to save. And also because research into the 33 species of small wildcats isn’t funded at anywhere near the levels of their big cat relatives.
“We have thousands of detections of tigers on camera traps, even though they are a critically endangered species,” notes Wai-Ming Wong of Panthera. “But we have maybe 15 or 20 of the clouded leopard [Neofelis nebulosa] which occupies the same habitat.” With so few detections, the usual statistical analyses can’t be applied to these smaller species, explains Wong.
One solution for building knowledge of small cat species is the collection of environmental DNA samples from soils or waterbodies. To get population baselines — and detect hybridization — scientists need to analyze genetic materials at the species and individual level, and compare genetic relatedness.
“Genetics will be a key method for us to be able to understand the wildcats’ ecology,” Wong says. Without this fundamental data, it’s hard to accurately assess threats to these species and make conservation management plans.
Although big cats have long captured the public’s imagination, Wong thinks small wildcats are charismatic and capable of capturing people’s hearts. At his conservation talks, every time people see pictures of Asia’s Pallas’s cat (Otocolobus manul) — dubbed “the original grumpy cat” — he says they’re immediately captivated and want to know all about it.
With their mid-level trophic role in ecosystems, acting as both predator and prey, small wildcats are important sentinels for detecting ecosystem degradation. They can also be vital for rodent and small mammal control (critical to balanced ecosystems and to helping farmers protect crops at no cost). Perhaps, with some creative public relations work, small wildcats could become ambassadors for threatened habitats the world over.
Wong sees hybridization as an emerging threat to small cat species — occurring naturally in some populations and catalyzed by humans in others. One thing that’s clear, says Wong, is that each small wildcat species has its own unique set of challenges. “That means there’s no one-size-fits-all approach to their conservation,” he says.
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