“Black leopard!” I squealed as if the others watching the animal on the computer screen would mistake it for a panda or rhino. It lifted its long agile tail and squirted the granite boundary post that showed where forest land began. The sprayed stone now doubled as a territorial marker for the leopard. In another video from the camera trap, it strode down the middle of the path in daylight, like a shadow without a body.
For years, I’ve grumbled about the number of black animals in thick forests. My photographs of Nilgiri langurs, sloth bears, and gaur show blobs of different shapes and sizes. Biologists say dark hides render them virtually invisible in the low light of the jungle, but that didn’t stop me from wishing—if only the animals sported vividly coloured coats that contrasted against the green and brown foliage. I would have been happy to see a golden, spotted leopard, but this unusual dark morph was special since it had padded to less than 500 metres from where I had spent the night at the Agumbe Rainforest Research Station, Karnataka. Besides, the chance of encountering it in the flesh and taking a photograph were as good as none in that forest.
In recent years, Karnataka and Chhattisgarh have boasted of these unusual creatures. Tiger expert Ullas Karanth told India Today in 2012 that several images of black leopards come from Dandeli-Anshi Tiger Reserve, Karnataka. But the colour morph is rare on the African continent where it would stand out against the sparse savannah vegetation. Little wonder then that a black leopard in Kenya made news around the world in 2019. At the other extreme is the Malay Peninsula, where the only leopards triggering camera traps are black.
People lucky enough to have examined the dark pelts of these cats say they aren’t totally black and their traditional skin pattern shows up under bright light. Apparently, a leopard cannot change its spots, but it can hide them. An overdose of melanin, the biological pigment that darkens human skin and hair, does the same for the cats. However, in felines, it is the result of inheriting a recessive genetic mutation.
For decades, scientists puzzled over the wide variety of patterns in feline coats. Since cats are usually nocturnal, they thought stripes, spots, rosettes, and shades of brown made them cryptic, aiding their ability to creep up to their prey unnoticed, hide from larger cats that could kill them, or both. But clothed in the colour of the night, they virtually disappear.
Black, however, can hide animals even in broad daylight. Indeed, the ghostly leopards of the Malay Peninsula hunt by day, a time when the tiger, their arch nemesis, rests. For this reason, leopards aren’t the only cats to have a streak of melanism. As many as 14 wild cat species out of 40 have a dark morph. Black colour erases their distinctive patterns, giving the animals a uniform hue from the tips of their ears to the ends of their tails.
Although rumours of black tigers circulate, such beings seem to be extremely rare.
If the dark colour allows smaller cats to shift their activity to daytime, and avoid their larger antagonists, why isn’t it more common within these species?
Another species, the Asian golden cat, a resident of the humid forests of Northeast India and Southeast Asia, may offer a clue. Arunachal Pradesh’s Dibang Valley has six types — golden, grey, black, cinnamon, spotted, and closely spaced rosettes. Like leopards, these golden cats’ default colour is amber. Each colour variation prefers to hunt at a specific time and a different elevation in the vast wilderness that is three times the size of Goa. After dark, the patterned and grey morphs venture out through rhododendron forests and alpine meadows above 3,000 meters. The plain unpatterned ones prowl during the day in the wet tropical forests below 1,700 metres. The different coat colours and designs allow the species to blend with a diverse range of habitats and under varying light conditions.
Except for the Malay Peninsula, black leopards are a minority and appear to live alongside other leopards. Like many forest-dwelling cat species, spotted leopards and Asian golden cats use the light-reflecting white spots behind the ears to communicate silently even in the dark of the jungle. Seen from behind, these patches glow like large eyes, perhaps to deter predators. And they act like beacons for their cubs following on their heels. These spots vanish when their mother flattens her ears in irritation or threat, and the young probably respond by stopping in their tracks, to avoid aggravating her or stay safe from danger. The cats swivel their ears to present the startling white to threaten rivals. In the same way, they may also twitch their banded tails, flashing the white underside, to advertise their intent to mates, rivals, and young.
Dressed all in black, from whiskers to tail tip, black cats have no white spots and may be at a disadvantage in the communication department. In dull light, they lose their ability to signal their mood to rivals and mates, while mothers cannot control their cubs. Like Tar-baby in the Uncle Remus folk tale, black cats “don’t say nothing”. Perhaps visual muteness makes them socially inept, unable to communicate with mates and competitors, which may explain why melanism isn’t common within species.
Throughout their Asian range, evolution weighs the relative merits of each option. Spotted leopards communicate better, but at night, when they are at their obscure best, they hazard confrontations with tigers. However, black morphs of leopards and golden cats hunt by day more often than patterned ones, and escape the attention of the larger striped cats, but perform dismally at expressing themselves. Each form has its costs and benefits, and evolution thus maintains the two colour variations.
The unusual phenomenon of all-black leopards in the Malay Peninsula may be driven by other factors. It could be natural selection, something about the environment drives the success of the black form at the expense of the spotteds. Or a case of genetic drift, when the repeated random selection of the dark form may have swamped a small population. Relatively few immigrant leopards made it across the 60-km-long Isthmus of Kra, the narrowest point on the long arm of the peninsula, to the southern tip. The impoverished gene pool could have skewed the entire resident group towards melanism.
I imagine if the indigenous Orang Asli hunters of the Malay Peninsula were to see a regular panther, they’d squeal “Spotted leopard!”
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