Humans weren’t the only creatures to fall under the sway of free love in the 1960s. After 2,000 years of keeping one another at paw’s length, wildcats and their domestic cousins began to interbreed about 60 years ago, a new study suggests.
Doing so may have helped to protect their offspring against diseases harboured by domestic cats, but this interbreeding is now threatening the survival of wildcats as a distinct species.
Domestic cats are generally considered to have descended from Near Eastern wildcats that prowled the Fertile Crescent of the Middle East back when early human farmers began storing grain. They arrived in Britain – where European wildcats also lived – about 2,200 years ago.
Today, hybridisation between wild and domestic cats is pushing the Scottish wildcat population to the brink of extinction, because the genes that define them are being “swamped” by those from hybrid and domestic cats.
“Not only are we at risk of losing a species from Britain, we’re potentially replacing it with hybrid and feral domestic cats that may be not as well adapted and may not perform the same ecological role in their habitat,” said Jo Howard-McCombe of the University of Bristol and the Royal Zoological Society of Scotland (RZSS).
“It is important to understand the history of this process, so that we can be better informed to manage that threat into the future.”
To investigate when this interbreeding started, Howard-McCombe and her colleagues analysed genomic sequences from wild and domestic cats, including 48 modern felines and 258 ancient samples excavated from 85 archaeological sites over the last 8,500 years.
The results, published in Current Biology, suggested that these creatures broadly avoided sexual contact with one another until the late 1950s, when rates of interbreeding between wild and domestic cats in Scotland rose rapidly – possibly as a result of dwindling wildcat populations.
“If you have a population of wildcats that’s being completely eradicated, those that are left are going to want to mate with something, and if the only thing that’s around are domestic cats, that’s probably what they’re going to choose,” said Prof Greger Larson at the University of Oxford, who contributed to the research.
In the short term, this may have benefited their offspring: domestic cats carry diseases that can also affect wildcats, and many of the genes that have accumulated in the hybrid cats relate to immune system function. “They may have helped to prevent the acquisition of those diseases, or at least make diseases not so bad,” Larson said.
However, the longer-term consequence could be the loss of European wildcats from Scotland and other areas. Today, no wild-living or captive Scottish wildcat is thought to be entirely free of domestic cat ancestry, but the descendents of a captive breeding programme initiated by RZSS during the 1960s may be the closest thing to a pure breed.
Nineteen of these wildcats were recently released into a pine forest in the Scottish Highlands in the first phase of a project to rescue the species. Provided such captive-bred cats have a large enough area of wilderness to establish themselves in and breed, they should be spared the seductive lure of the domestic cat.
However, to bolster their chances, Howard-McCombe advises local cat owners living nearby to get their pets neutered and vaccinated against common diseases.
