New survey gives hope to the Critically Endangered Sumatran tiger

A new study, published in the scientific journal PLoS ONE, has provided a rare glimmer of hope for the Sumatran tiger, the last subspecies of tiger still in existence in Indonesia.

Reports that tiger populations are declining in many parts of its range paint a bleak and all too familiar picture. Of the 13 tiger range countries recognised today, the Indonesian archipelago has already lost two distinct subspecies from the islands of Bali and Java.

Reliably determining where tigers are present within dense tropical jungle is challenging because their secretive behaviour and excellent camouflage naturally make them difficult to detect.

For the past three years, eight NGOs have joined forces to carry out the first ever Sumatra-wide survey, in collaboration with the Indonesian Ministry of Forestry.

Lead author Hariyo Wibisono of the Wildlife Conservation Society (WCS) and Chairman of the Sumatran Tiger Forum (HarimauKita), which coordinated the initiative, said, “This survey is a milestone for Sumatran tigers. The results provide the most up-to-date and reliable information ever collected for this Critically Endangered species and is the first time that such a large number of organisations have worked together so effectively.”

Over 13,500km of forest transects were surveyed for indirect signs of tigers and their prey, an impressive feat given that the entire length of Sumatra is only 1,900km.

Scientists measured the tiger’s spatial distribution within 394 sampling grid cells (of 17 x 17km) covering forest habitats at different elevations and under varying threats.

The study found that while over 70% of forest patches surveyed were occupied by tigers, its status varied greatly between the different landscapes.

Speaking about the newly created 3.3 million hectare Leuser-Ulu Masen landscape in Aceh Province, co-author Dr Matthew Linkie from Fauna & Flora International explained, “This study puts Aceh’s previously unsurveyed forest firmly on the map as a global priority for wild tigers in Asia.”

Another positive finding was the wide distribution of tigers found in the second largest landscape: the 1.6 million hectare Kerinci Seblat-Batang Hari. The size of the area, combined with a decade of Tiger Protection and Conservation Unit forest patrols there, have shown how resilient tigers can be under the right conditions.

In some areas however, the impact of deforestation was obvious, with tigers largely missing from severely degraded forest patches.

Dr Sunarto, who led the World Wildlife Fund (WWF) team in Riau Province, warned of the perilous situation facing Sumatran tigers: “Over the past 25 years, Riau has lost 65% of its natural forest, so it’s unsurprising that tigers are badly affected here. However, they are still roaming and breeding in some places, so we’re increasing our conservation efforts in these areas and trying to restore forest corridors between tiger subpopulations.”

The participating NGOs and their government partners will use this new-found information to enhance their management strategies (such as law enforcement patrolling) in priority areas, as well as working towards increasing tiger populations in degraded areas.

Looking to the future, co-author Dr Joseph Smith of Panthera explained, “The survey results provide an excellent benchmark against which to measure how our future conservation efforts are benefiting tigers on the ground.”

Download the press release (PDF) to learn more.