The smallest member of the cat family, the rusty-spotted cat, was sighted in the Pilibhit Tiger Reserve of Uttar Pradesh earlier this year. The sighting of the kitten – a seemingly leucistic one – sent ripples of excitement among those who had spotted it and the officials of the protected area.
The status of leucism in the cat, however, remains contentious after scientists working on wildcats for a long time said that the variation was nothing but a commonly found difference in coat colours. Leucism is the lack of melanin pigmentation in all or some parts of the skin of animals due to a series of defects in melanin-producing cells (melanocytes).
Classified as “near threatened” by the International Union for Conservation of Nature, the rusty-spotted cat (Prionailurus rubiginosus) is called the ‘hummingbird of cats’ owing to its tiny stature – weighing just about 0.8 to 1.6 kg with a body length of around 35 to 48 cm and a tail extending from 15 to 25 cm.
Mayank Jaiswal, a freelance wildlife photographer, who spotted and clicked pictures of the otherwise nocturnal species, in broad daylight at Pilibhit Tiger Reserve, was first confused about its identity owing to its lighter appearance.
“I thought it was a fishing cat as its coat was lighter than a normal rusty-spotted cat. I sent the photos to wildlife biologists who confirmed that it was indeed a rusty-spotted cat and a rare leucistic individual of the species,” Jaiswal told Mongabay-India.
While the rusty-spotted cat has brownish-grey fur with reddish spots the individual spotted in the tiger reserve was said to have a lighter-coloured coat, giving it a yellowish appearance, leading to confusion about it being leucistic.
“Pigmentation (melanism, albinism and leucism) is widespread in wild cats,” said Nilanjan Chatterjee, statistical ecologist, and post-doctoral fellow at the Senckenberg Biodiversity and Climate Research Center and University of Minnesota. “Multiple studies have found that pigmentations (specifically melanism) occur due to changes in two genes. Wild cat species like leopard, jaguar and jaguarundi are known for their melanistic coats and most likely it helps them survive by not getting detected in the wild. On the other hand, albinism and leucism have not been reported to help survival and those individuals are usually not selected over generations.”
After the sighting of the elusive cat, Naveen Khandelwal, then the director of the Pilibhit Tiger Reserve, ordered setting up camera traps in the area to monitor its movements to protect its habitat in the protected area.
“We have closed the area for the protection of these elusive species and set up 15 camera traps in a five km sq area. We saw the same kitten again on camera a few days later. It has a lighter coat than others of its kind, which is even rarer,” Khandelwal told Mongabay-India.
However, scientists working on small cats in India have raised doubts about the leucistic state that is being attributed to the kitten.
Shomita Mukherjee, Principal Scientist at Salim Ali Centre for Ornithology and Natural History, who has been studying the species for over two decades now, after looking at the photos, expressed uncertainty about terming it as a “leucistic” variant.
“Such colour variations are normal in wildcats and this is not a leucistic individual. This is a normal rusty-spotted cat, but its tail looks bushier. Perhaps, the winter coat has not moulted away, which might be the reason for the slight difference in its colour,” she said to Mongabay-India in a telephone conversation.
Similar thoughts were reiterated by Chatterjee who was one of the authors of the paper on the population density and habitat of the rusty spotted cat and the jungle cat in central India, published in PLOS ONE.
“Leucism in wild populations does indicate some genetic variation. But this (the individual in the photographs) does not indicate a leucistic individual. The usual coat colour of the species looks like that. Moreover, small/medium cats are known for their coat colours, specifically species such as the Asiatic golden cats. Although there are some existing hypotheses, we do not know completely yet how that works at a genetic level,” said Chatterjee.
Another wildlife biologist Sumit Dookia, who earlier was also boggled by the lighter appearance of the coat colour said that if more such individuals are found in the area in future, it might make for an interesting study.
“The reason behind the slight colour variations in the coats is not properly known, which leads to such confusions. It would be interesting to monitor the population of the lighter-coated rusty-spotted cats in the region and conduct a study by collecting their genetic materials to understand this colour variation. But it will only be possible if we find more such individuals in this area in the future,” he said.
This article was first published on Mongabay.
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