for National Geographic News
Braving falling trees, snakes, leeches, and other dangers, intrepid researchers have used camera traps to produce the first reliable count of Malaysian tigers. The study is one of few detailed ecological studies attempted for Southeast Asian tigersperhaps the least-known of all tiger populations.
Conservation scientist Kae Kawanishi, formerly of the University of Florida in Gainesville, and a team of local assistants, spent three years arranging and maintaining automatic cameras that captured the images they required.
The team had the tigers of West Malaysia's Taman Negara National Park in their sights. The 4,350-square-kilometer (1,677-square-mile) park is among Southeast Asia's largest reserves.
Difficult to Count
Camera traps are a new line of attack for biologists working against the odds to count one of the most awe-inspiring and elusive carnivores. Kawanishi, who completed the project for her doctorate last year, is now submitting her findings for publication in research journals.
Despite the relatively pricey machinery (the cameras cost U.S. $450 or more apiece), the method may be widely applicable. "It's been tried successfully in at least India and Sumatra, and theoretically could be used across the species' range," said Kawanishi, who is now with the Malaysian Department of Wildlife and National Parks Division of Research and Conservation in Kuala Lumpur. "The same innovative method is being used to estimate the population size of jaguars in Latin America and amur leopards in Russia," she said.
Basic information on ecology, distribution, and population size are essential for conservation of the world's remaining tigers. Estimates suggest 5,000 to 7,000 remain, said Kawanishi. "But who knows, it's not based on good science." She does have more confidence in estimates that Panthera tigris has lost more than 95 percent of its original range during the last few centuriesthe range now spans 160 isolated forests in 12 countries from Siberia to Sumatra.
Traditional counting methods include the track mark counting method used extensively in India, as well as radio-collar tracking methods. The former method requires wildlife workers to find, compare and count tiger paw prints. However, a recent study from some of the world's top tiger workers, published in the journal Animal Conservation argues that this method has produced inaccurate and unreliable data and led to bad conservation practices. Neither method is suited to rainforest where vegetation smothers radio signals, and tracks are difficult to locate or disappear rapidly.
To get the required basic data for conservation planning, between 1998 and 2001 Kawanishi and her team set up 150 cameras across three different sites, each spanning 200 square kilometers (75 square miles).
Tigers have distinctive stripes, but to ensure identification both flanks must be photographed. So, camera traps were used: with several cameras facing one another along much-trafficked wildlife trails. Passing tigers, rhinos, tapirs, deer and other animals triggered the shutter by tripping infrared sensors.
Trapping images has been proved a more reliable method in India than the traditional track mark count. By examining how frequently an animal is recaptured, it's possible to use well-established population models to estimate total population sizes.
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