PRANBURI, Thailand // They're better known as stealthy killing machines to take out suspected terrorists with pinpoint accuracy. But drones are also being put to more benign use in skies across several continents to track endangered wildlife, spot poachers and chart forest loss.
Although it's still the "dawn of drone ecology", as one innovator calls it, these unmanned aerial vehicles are already skimming over Indonesia's jungle canopy to photograph orangutans, protecting rhinos in Nepal and studying invasive aquatic plants in the US state of Florida.
Activists launched a long-range drone in December to photograph a Japanese whaling ship as the Sea Shepherd Conservation Society attempted to block Japan's annual whale hunt in Antarctic waters.
Relatively cheap, portable and earth-hugging, they fill a gap between satellite and manned aircraft imagery and on-the-ground observations, says Percival Franklin at the University of Florida, which has been developing such drones for more than a decade.
"The potential uses are almost unlimited," says Ian Singleton, director of the Sumatran Orangutan Conservation Programme, testing drones this year over Indonesia's Tripa peat forest where fires set by palm oil growers are threatening the world's highest density habitat of the great apes.
Conservation is one of the latest roles for these multitaskers. Ranging in size from less than half a kilogram to more than 18 tonnes, drones have been used for firefighting, road patrols, hurricane tracking and other jobs too dull, dirty or dangerous for piloted craft. Most prominently, they have been harnessed by the US military in recent years, often to detect and kill opponents in America's "war on terror".
A conservation drone pioneer, Lian Pin Koh of the Swiss Federal Institute of Technology, says the idea came to him after another sweaty, jungle slog in Sabah, Malaysia, hauling heavy equipment for his field work.
"I told my assistant, who happened to be my wife, 'How wonderful it would be if we could fly over that area rather than walk there again tomorrow,'" recalled the Singaporean expert on tropical deforestation, and a model plane hobbyist.
Unlike eco-drones in the United States, mostly custom-built or commercial models, Mr Koh last year cobbled together a far cheaper, off-the-shelf version that poorer organisations and governments in the developing world can better afford.
He and partner Serge Wich bought a model plane - some are available in China for as little as US$100 (Dh367) - added an autopilot system, open source software to programme missions, and still and video cameras. All for less than $2,000, or 10 times cheaper than some commercial vehicles with similar capabilities. This year, they have flown more than 200 mostly test runs in Asia using an improved version with a 2-metre wing span, airtime of 45 minutes and a 25-kilometre range.
The drones were flown over rough terrain in Malaysia where GPS-collared elephants are difficult to monitor from the ground. In Nepal's Chitwan National Park, the World Wide Fund for Nature and the Nepal army conducted trials on detecting rhino and elephant poachers. The duo also assisted the Ugalla primate project to head count chimpanzees in western Tanzania. "Counting orangutan nests is the main way of surveying orangutan populations," says Graham Usher of the Sumatran project, which captured one of the apes atop a palm tree feeding on palm heart in a sharp photograph. From higher altitudes the drones, he said, also provide high-resolution, real-time images showing where forests are being cleared and set ablaze.
By contrast ground expeditions are time-consuming, cumbersome and expensive. A conventional orangutan census in Sumatra, which may also involve helicopters and aircraft, costs about $250,000. Surveying land use by satellite is likewise costly and hampered by frequent cloud.
But there are drawbacks with drones, including landing them in thickly vegetated areas since they need clear touch-down zones of about 100 by 100 metres. Mr Koh said he was working to rig the vehicle with a parachute to allow landing in confined space.