LEUSER, Indonesia (AFP) - In the depths of Indonesia's dense Leuser rain forest, a group of rangers are searching for traps set by poachers which are endangering rare wildlife.

Scientists and conservationists consider the Leuser Ecosystem, which falls mostly within Aceh province on Sumatra island, to be among the most important forests left in Southeast Asia.

It is the last place of sufficient size and quality to support viable populations of rare species like orangutans, Sumatran tigers, rhinoceroses, elephants, clouded leopards and sun bears.

In 2015 hundreds of traps were confiscated monthly in Leuser but now fewer than 10 are found every month, according to local conservation NGO Forum Conservation Leuser.

"The rangers are trained to track signs indicating that there were poachers in the area, such as by looking for cigarette ends or footsteps," said Rudi Putra, head of the forum.

Some traps are designed to snare animals' feet. Others consist of spears set high up in trees, which would fall when a trap is sprung.

The rangers also watch for signs of deforestation such as illegal logging, and collect data from the forest for further research.

Poachers typically set up traps to capture elephants, tigers and bears so they can sell them illegally and make money.