Leopards, found from the frozen forests of Russia to the scorching sands of the Kalahari Desert, are the most widely distributed large cat on earth. Their iconic spotted coat has been admired and coveted by humans for millennia. However, in just one region in their vast range, mysteriously the leopards are almost all entirely “black” or melanistic – the Malay Peninsula. This dark colouration sometimes hides the spotted pattern which all leopards have; the spots just don’t stand out clearly in melanistic individuals.
“This is a completely unique phenomenon for leopards, and represents perhaps the only known example of a mammal with almost an entire population completely composed of the melanistic form of the species” says Laurie Hedges, lead author of a study who just published a population density estimate on these animals in the Journal of Wildlife Management.
Melanism is a trait which can be found across many mammal species, and especially in big felids. Though theories, ranging from the explosion of Mount Toba in Sumatra to competition with tigers, have been put forward to explain how this unique melanistic population has come about, scientists are still puzzled…
“Despite the uniqueness of this population, very little was known about leopards in Malaysia, until now. This is mainly because their uniformly black colouration prevented us from identifying individual animals and estimating their population sizes with conventional flash camera traps.” says Dr. Mark Rayan Darmaraj, who manages WWF-Malaysia’s tiger conservation project in the Belum-Temengor Forest Complex.
In 2013, Rimba’s researchers from Project Black Cloud developed a simple technique that solved this problem.
“Many brands of camera traps use an infrared flash to illuminate their subjects. During the daytime, when no flash is used, the different leopard individuals are indistinguishable,” says Dr. Gopalasamy Reuben Clements, a co-author of the study based in James Cook University and Universiti Malaysia Terengganu. “However, at night, the characteristic spotted pattern of leopards can be seen on their coat. All we did was place a piece of sticky tack placed over the light sensor of the camera. This simple technique ‘tricks’ it into thinking that it is night and thus triggering the infrared flash.”
The researchers tested this method in the Kenyir Wildlife Corridor, which is situated in the north-east state of Terengganu in Peninsular Malaysia.
“Forcing cameras into ‘night mode’ allowed us to accurately identify 94% of the animals, which enabled us to get an estimate of the population size. We can now monitor this population each year to get a sense of whether leopards in the region are increasing in numbers, or whether they are in decline.” says Laurie.
Now that individual melanistic leopards can be identified, the status of their populations in Malaysia and elsewhere can be determined. This is timely, as there are worrying signs that, as with tigers across Southeast Asia, leopards may be starting to disappear. “Some places in Peninsular Malaysia where I have camera-trapped relatively abundant levels of prey and forest cover, alarmingly, turned up little or no evidence of leopards,” says Dr. Ahimsa Campos-Arceiz, an Associate Professor based at the University of Nottingham Malaysia Campus.
The most likely reason – humans actively trapping and killing leopards as well as other animals using wire cable snares. “In recent years, carcasses of leopards, all bearing the characteristic signs of injuries inflicted by snares, have been discovered in Malaysia.” says Laurie.
There is even an increasing trend where leopard skins and body parts are showing up in wildlife trading markets in places such as Mong-la on the Myanmar-China border, which is a well-known hotspot for the illegal trade in wildlife.
At the same time, suitable habitats are disappearing in Malaysia at a faster rate than perhaps anywhere else in the leopard’s range as forests are cut down for timber and replaced with oil palm and rubber plantations.
“Understanding how well leopards are faring in human-dominated landscapes in Malaysia is vital. Currently we do not have an idea of their population size or trends,” says Dr. William Laurance, a co-author who is Distinguished Professor based in James Cook University. “Ultimately, this novel technique can also benefit researchers in both Thailand and Java, where substantial numbers of melanistic leopards can be found in smaller proportions.”
Below are some of the media websites that have covered this:
IFL Science (Facebook post was not accurately headlined)
New Scientist (not accurately reported)
The Huffington Post (not accurately reported)