A new joint study led by Nanyang Technological University, Singapore (NTU Singapore) has warned about the extinction of Sumatran tigers in Sumatra, Indonesia, due to destroyed habitats.
The scientists found that while tiger population densities have increased in well-protected forests in Sumatra, 17 percent of the tigers' habitats were deforested from 2000 to 2012 to make way for oil palm plantations.
Published in Nature Communications on 5 Dec, the new paper suggests anti-poaching efforts has helped to increase tiger population densities. In short, the conservation efforts work, but only if tiger habitats are well protected at the same time.
Dr Mathew Luskin, a research fellow at NTU's Asian School of the Environment, led the study in partnership with researchers from the Smithsonian Institute and the San Diego Zoo Global in the United States, as well as the Fauna and Flora Institution in Indonesia.
"Our results are a mixed bag for tigers. The loss of key tiger habitats is causing significant conservation challenges for Sumatra - and in particular for this critically endangered species," explained Dr Luskin.
Dr Mathias Tobler from San Diego Zoo Global, who is the senior author of the study, said, "Safeguarding the remaining expanses of primary forests, such as Gunung Leuser National Park, is now absolutely critical to ensuring tigers can persist indefinitely on Sumatra. Large-scale reforestation is unlikely. If we are going to save Sumatran tigers in the wild, the time to act is now."
Dr Stuart Davies, Director of The Center for Tropical Forest Science - Forest Global Earth Observatory (Forest-GEO) at the Smithsonian Institute, said, "This study illustrates that long-term, field-based observations are essential to supporting the conservation of our most iconic and threatened animals and plants."
How the study was conducted
Obtaining information on the rare, stealthy predators is not easy - especially in dense uncharted jungles.
The research team spent a year conducting expeditions through remote forests, mounting hundreds of motion-activated cameras. On the resulting footage, tigers are identified by their unique pattern of stripes, allowing the researchers to track their movement.
There are about 618 tigers estimated to be left in Sumatra and the scientists calculated that a Sumatran tiger's territory size, also known as home range, is about 400 square kilometres.
This is up to four times larger than the average tiger's home range in regions such as India, where it is about 100 square kilometres. Sumatran tigers may need larger areas to find rare prey species such as muntjac deer.
The team developed new methods to estimate the number of tigers in each remaining patch of forest in Sumatra.
Tiger densities were 47 percent higher in primary versus degraded (logged) forests. Tigers could prefer primary unlogged forests or there might be less poaching there.
They found that there are now only two habitats large enough to host viable tiger populations over the long term: Gunung Leuser and Kerinci Seblat National Parks.
The study suggests that the population density of tigers has doubled over the last 15 years due to effective anti-poaching programmes. However, packing more tigers into disappearing forest does not reduce the threat of extinction.
The scientists are also concerned that the forests included in the study may have the best protection and are not representative of the 'average Sumatran forest'. They urged a cautious interpretation of increasing densities.
Between 1990 and 2010, Sumatra lost 37 percent of its primary forest. The clearing of pristine lowland forest has disproportionately reduced tiger numbers.
"The erosion of large areas of wilderness pushes the Sumatran tigers one step closer to extinction, so we hope this serves as a wake-up call," Dr Luskin added.
Associate Professor Fidel Costa, Acting Chair of NTU's Asian School of the Environment, said this paper is one of several new projects where NTU leverages on the Smithsonian Institution's unique research legacy and capacity in the region. "Together with the Smithsonian, NTU aims to provide the scientific research expertise necessary for Asian countries to conserve their biological heritage, such as tigers," Prof Costa explained.
"Our ongoing research include examining the secondary effects of losing tigers for other animals, such as their prey species, and even for tree communities. And the future findings will provide actionable insights into current conservation efforts, helping to guide policymakers on how to improve these efforts to better protect our environment for future generations."
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Nanyang Technological University
About Nanyang Technological University, Singapore
A research-intensive public university, Nanyang Technological University, Singapore (NTU Singapore) has 33,500 undergraduate and postgraduate students in the colleges of Engineering, Business, Science, Humanities, Arts, & Social Sciences, and its Interdisciplinary Graduate School. It also has a medical school, the Lee Kong Chian School of Medicine, set up jointly with Imperial College London.
NTU is also home to world-class autonomous institutes - the National Institute of Education, S Rajaratnam School of International Studies, Earth Observatory of Singapore, and Singapore Centre for Environmental Life Sciences Engineering - and various leading research centres such as the Nanyang Environment & Water Research Institute (NEWRI), Energy Research Institute @ NTU (ERI@N) and the Institute on Asian Consumer Insight (ACI).
Ranked 11th in the world, NTU has also been ranked the world's top young university for the last four years running. The University's main campus has been named one of the Top 15 Most Beautiful in the World. NTU also has a campus in Novena, Singapore's medical district.
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San Diego Zoo Global
Bringing species back from the brink of extinction is the goal of San Diego Zoo Global. As a leader in conservation, the work of San Diego Zoo Global includes on-site wildlife conservation efforts (representing both plants and animals) at the San Diego Zoo, San Diego Zoo Safari Park, and San Diego Zoo Institute for Conservation Research, as well as international field programs on six continents. The work of these entities is inspiring children through the San Diego Zoo Kids network, reaching out through the internet and in children's hospitals nationwide. The work of San Diego Zoo Global is made possible by the San Diego Zoo Global Wildlife Conservancy and is supported in part by the Foundation of San Diego Zoo Global.