A simple modification to infrared cameras used to monitor wildlife has enabled scientists to record the intricate – and individual – rosette markings of Malaysia’s black leopards.
It’s also allowed them to conduct the first census, or density estimate, of black leopards (Panthera pardus) on the Malay Peninsula, which will provide critical ecological evidence to protect their habitat from logging and clearing for rubber plantations.
Although researchers had been using camera traps for several years to study the movements of the leopards, it was almost impossible to identify individual animals.
The camera footage showed a uniformly melanistic, or black, big cat and didn’t pick up the complex markings hidden beneath the dark fur.
But researchers based at James Cook University and the University of Nottingham in Kuala Lumpur have developed a technique to manipulate the infrared camera mechanism to operate continuously in “night” mode.
“Most automatic cameras have an infrared flash, but it’s only activated at night”, says Dr Gopalasamy Reuben Clements from JCU.
“However, by blocking the camera’s light sensor, we can fool the camera into thinking it’s night even during the day, so it always flashes.”
Using the infrared flash, the cameras were able to pick up the unique patterns of spots which allowed the researchers to identify individual animals and estimate population numbers.
The results of camera study are published online in the Journal of Wildlife Management.
“Our estimates represent the first density estimate of leopards in Malaysia and arguably, the world’s first successful attempt to estimate the population size of a species with melanistic phenotypes,” the research paper says.
“Because we have demonstrated that melanistic leopards can be monitored with confidence using infrared cameras, future studies should employ our approach instead of relying on scars or body shape for identification.”
According to the paper, Malyasia’s black leopards face an increasing number of threats to their survival. These include poaching, snare traps, illegal clearing and loss of habitat to rubber plantations.
Dr Clements is the co-founder of Malaysia’s jungle conservation organisation Rimba, which was set up in 2010 as a non-profit research group.
In a statement on Rimba’s website , he explains the simple trick behind the breakthrough.
“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,” he says.
“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 over the light sensor of the camera.
“This simple technique ‘tricks’ it into thinking that it is night and thus triggering the infrared flash.”