A recent study has once again looked at the concerning situation regarding the extinction of the Scottish wildcat which is actually a European wildcat living in Scotland. About 15 years ago scientists knew that the Scottish wildcat was near extinction because of hybridisation with domestic and feral cats in Scotland.
Acceleration of wildcats mating with domestic cats since 1950s
This recent study has concluded that hybridisation has been a major issue since the 1950s. Before I go on, I will add that the word “hybridisation” in this context means purebred Scottish wildcats living in the ‘wild’ in Scotland mating with domestic and feral cats from human settlements in Scotland. In other words, the hybridisation is thanks to humans bringing cats to the area, some of those domestic cats becoming feral or stray eventually and then the feral/stray cats mating with purebred Scottish wildcats. That’s how it works.
Appearance of coat
The scientists can work out the kind of hybridisation which has occurred by looking at the coat of the cats and how the first filial cats look different to the purebred Scottish wildcat. There is a subtle appearance difference in the “pelage” as the scientists describe the coat markings.
And the process of cross-mating gradually erodes the purebred genes of the Scottish wildcat to the point where the wildcat becomes “genomically extinct”. In other words, looking at the total genetic makeup of the Scottish wildcat, the experts always see some domestic cat genes.
No ‘unadmixed’ cats
There are no purebred Scottish wildcats left because in this study “we have found no unadmixed individuals”. The word “unadmixed” means” no wildcats to which the genes of domestic and feral cats have been added. And on that definition, according to a scientist called Allendorf, the Scottish wildcat is effectively extinct at this time.
Reasons for wildcats mating with domestic/feral cats
The underlying reasons why there has been a sharp increase in hybridisation of the Scottish wildcat since 1950s is because the population of the wildcat in Scotland dropped to about 70 individuals because of what the experts call a “bottleneck”.
Since that time, the area where the Scottish wildcat was found expanded over the 20th century from a small area in the north-west Highlands into central Scotland. This allowed the Scottish wildcat to meet up with domestic and feral cats. It is regarded as “a proposed driver of the introgression in continental wildcat populations”. The word “introgression” means the transfer of genetic material from one species to another. In other words, hybridisation of the wildcat with the domestic cat.
There are other factors which brought the Scottish wildcat and the domestic cats together. A breakdown in habitat would be another factor. Lack of prey would be another factor. Persecution, urbanisation and land-use change including agriculture would be other influences resulting in the mating of domestic and wild cats.
Very small population size and inbreeding depression
This study found that the captive wild cats were more purebred than the wildcat in the wild. They also decided that the mating of wildcats with domestic cats in some ways has saved the Scottish wildcat while at the same time making it extinct. That sounds peculiar but at 70 individuals the population was so small that there was inbreeding depression. That means that the population became inbred or was becoming inbred which can affect the health of the individuals as immune system becomes ‘depressed’ (compromised). This is a problem which occurs in the selective breeding (artificial selection) of the cat breeds such as Maine Coons and Persian cats for example.
The scientists believe that “disease transmission is an important potential driver of selection in wildcat populations, and hybridisation provides a mechanism for the transfer of pathogen resistance from domestic cats.”
Scientists also suggested that in combating inbreeding depression it might be useful to cross Scottish wildcat with their European wildcat cousins on continental Europe. This would help to make their genes more diverse.
Selectively breed more almost purebred wildcats
Lastly, they decided that “our evidence demonstrates that the captive Scottish wildcat population and the wild-living hybrids retain almost the full ancestral genome required to reconstruct the original species, and these results will inform future conservation strategies.”
My interpretation of that is that it will be possible to create through selective breeding a near purebred Scottish wildcat in the future because the genes are there. But let’s be clear, that quote includes the words “almost the full ancestral genome”. That is very clear. It is saying that there are no Scottish wildcats left that are entirely purebred meaning that all their genes are those of the Scottish wildcat.
The study is called: “Genetic swamping of the critically endangered Scottish wildcat was recent and accelerated by disease”.
The link to the study is: https://doi.org/10.1016/j.cub.2023.10.026
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