BLACKSBURG, Va., Feb. 29 (UPI) -- Sumatran tigers are threatened by human disturbances of natural habitats that turn forests into agricultural plantations, U.S. researchers say.
Researchers at Virginia Tech and the World Wildlife Fund say their study is the first to systematically investigate the use of different land cover types -- not just natural forests but also plantation areas -- for tiger habitat.
Three of the world's subspecies of tigers are now extinct, the researchers said, and the Sumatran tiger is now seriously threatened in Indonesia.
Sumatran tigers strongly prefer forests over plantations of acacia and oil palm trees and tend to avoid plantation areas unless they contain thick ground-level vegetation and have extremely low levels of human activities, they said.
Tigers also strongly prefer sites closer to forest centers and farther from human activity centers such as bodies of water and forest edges, they found.
Most importantly, the study found, tigers have a strong predilection for sites with large amounts of vegetation cover at the ground level, known as understory over.
"As ambush hunters, tigers would find it hard to capture their prey without adequate understory cover," Sunarto, who earned a wildlife sciences doctorate at Virginia Tech in 2011, said.
"The lack of cover also leaves tigers vulnerable to persecution by humans, who generally perceive them as dangerous," Sunarto, now a tiger expert for WWF-Indonesia, said.
"As long as forest conversion continues, tigers will require active protection or they will quickly disappear from our planet."