Johannesburg - Researchers have found evidence of seven "strawberry leopards" in the north of South Africa in what is one of very few documented cases of these ultra-rare rare big cats outside India.The result of an extraordinary genetic twist, strawberry or erythristic leopards are slightly paler than other leopards. Their black spots are reddish brown.Some say these are the original "pink panthers", although Dr Mark Fellowes of the University of Reading UK, one of three authors of a recently-published paper on South Africa's strawberry leopards, isn't a fan of the nickname.He told News24: "They're strawberry in the sense of someone being strawberry blonde, that sort of reddish blonde hair colour. They look 'washed out' to me."Five of the leopards have been seen since 2012. Two were found in a wilderness reserve in Mpumalanga that has been the site of an intensive three-year study conducted by researchers from Reading with the support of Ingwe Leopard Research.Different mutationWith the help of rangers, conservationists and social media, researchers were able to document evidence of five other erythristic leopards.These leopards were found in Mpumalanga and North West province. Two were victims of road accidents, while one was shot sometime during the last 20 years. Its skin was given to a farmer.Before this study, the main records of strawberry leopards were from India, where a scientific paper published in 1993 said five leopards "with light brown spots" had been shot between 1905 and 1965.Fellowes says that so little was known about the presence of strawberry leopards in South Africa that the research team was taken by surprise when one showed up in a camera trap.He said: "To be honest, until we recorded the individual on the camera trap we weren't aware of this colour morph. We did some digging which resulted in us finding some records in the press."We were able to pull these together with our own records and a survey of knowledgeable people across South Africa."One of the strawberry leopards was born during the study and seen by doctoral researcher Tara Pirie, Fellowes confirmed. The cub's mother was not a strawberry leopard. These leopards are not albinos, Fellowes stresses. "It's a different mutation."Rare genes The colouring of leopards is already known to vary depending on geographical location. Leopards from densely-forested areas are darker and their spots are much closer together.Leopards living in arid regions tend to be paler with their spots further apart, likely for camouflage purposes. But that doesn't explain why the seven erythristic leopards found in this study got their spots, since Mpumalanga isn't an exceptionally arid place.Fellowes and his colleagues suspect the presence of these ultra-rare felines in the region may be to do with the pressures upon leopard populations and the in-breeding that results from it. While leopard hunting isn't legally allowed, some leopards are killed by farmers. Others are occasionally killed in road accidents."In normal large populations, rare genotypes don't show themselves," Fellowes says. "But when populations become fragmented then you end up with more related individuals mating with each other so rare genes can become expressed."