On Sunday, April 10th, the World Wildlife Fund (WWF) and Global Tiger Forum (GTF) issued a report stating that the world’s wild tiger population was on the rise, and on track for a doubling in a decade. We do not find this report1 and its implications scientifically convincing.
- Having devoted years of our lives to trying to understand and save wild tigers, we believe their conservation should be guided by the best possible science. Using flawed survey methodologies can lead to incorrect conclusions, an illusion of success, and slackening of conservation efforts, when in reality grave concern is called for. Glossing over serious methodological flaws, or weak and incomplete data to generate feel-good ‘news’ is a disservice to conservation, because tigers now occupy only 7% of their historic range2. A recent World Conservation Union (IUCN) assessment3 showed 40% habitat loss in the last decade, and a spike in poaching pressure in many regions. Cambodia, Vietnam, Lao PDR and China have virtually lost viable tiger populations in recent years. This is not a time for conservationists to take their eyes off the ball and pat each other on the back.
- There is no doubt that wildlife managers in parts of India and even in specific reserves in South East Asia and Russia have made commendable conservation efforts, leading to recoveries in specific tiger populations. India has invested massively in recovering several tiger populations2 over the last four decades. This has been possible because of strong political, administrative and public support rarely matched anywhere else.
- Such sporadic tiger recoveries should be monitored using statistically robust camera trap or DNA surveys. Rigorous scientific studies in India, Thailand and Russia4-6 demonstrate this can indeed be done. But these studies also indicate that tiger recovery rates are slow and not likely to attain levels necessary for the doubling of wild tiger numbers within a decade4-6.
- Estimates of tiger numbers for large landscapes, regions and countries currently in vogue in the global media for a number of countries are largely derived from weak methodologies7-9. They are sometimes based on extrapolations from tiger spoor (tracks and droppings) surveys, or spoor surveys alone. While spoor surveys can be useful for knowing where tigers occur, they are not useful for reliably counting their numbers. Translating spoor counts to tiger numbers poses several statistical problems that remain unresolved9, which can lead to fundamentally flawed claims of changes in tiger numbers7-9.
- Source populations of tigers that occur at high densities and which are likely to produce ‘surplus’ animals that can disperse and expand populations now occupy less than 10% of the remaining 1.2 million square kilometers of tiger habitat2. Almost 70% of wild tigers survive within these source sites. They are recovering slowly, only in some reserves4-6 where protection has improved. Outside these source sites lie vast ‘sink landscapes’, which are continuing to lose tigers and habitat due to hunting as well as rural and developmental pressures.
- With the above considerations in view, even taking these putative tiger numbers at face value, simple calculations show that doubling of the world’s tigers in ten years as hoped for in the report1 is not a realistic proposition. Assuming 70-90% of wild tigers are in source populations with slow growth4-6, such an anticipated doubling of global tiger numbers would demand an increase between 364-831% in these sink landscapes. We believe this to be an unlikely scenario.
- Rather than engaging in these tiger number games that distract them from reality, conservationists must now focus on enhancing and expanding recovery and monitoring of source populations, while protecting their remaining habitat and their linkages, all the while being guided by the best of science.
K. Ullas Karanth, Ph.D Director for Science Asia-Wildlife Conservation Society firstname.lastname@example.org
Dale Miquelle, Ph.D. Director, Russia Program-Wildlife Conservation Society email@example.com
John Goodrich, Ph.D. Senior Director, Tiger Program-Panthera firstname.lastname@example.org
Arjun Gopalaswamy, Ph.D. Research Associate, Zoology, University of Oxford, UK email@example.com
- WWF. Global wild tiger population increases, but still a long way to go. 2016.
- Walston J, Robinson JG, Bennett EL, Breitenmoser U, da Fonseca GAB, Goodrich J, et al. Bringing the tiger back from the brink—the six percent solution. PLoS Biol. 2010;8: e1000485.
- Goodrich J, Lynam A, Miquelle D, Wibisono H, Kawanishi K, Pattanavibool A, Htun, S., Tempa, T., Karki, J., Jhala, Y., Karanth, K U.. Panthera tigris. The IUCN Red List of Threatened Species 2015: e.T15955A50659951. 2015.
- Karanth KU, Nichols JD, Kumar NS, Hines JE. Assessing tiger population dynamics using photographic capture-recapture sampling. Ecology. 2006;87: 2925–2937.
- Duangchantrasiri S, Umponjan M, Simcharoen S, Pattanavibool A, Chaiwattana S, Maneerat S, et al. Dynamics of a low-density tiger population in Southeast Asia in the context of improved law enforcement. Conserv Biol. 2016; DOI: 10.1111/cobi.12655. doi:10.1111/cobi.12655
- Miquelle DG, Smirnov EN, Zaumyslova OY, Soutyrina S V, Johnson DH. Population dynamics of Amur tiger (P. t. altaica, Temminck 1884) in Sikhote-Alin Zapovednik: 1966-2012. Integr Zool. 2015;10: 315–328.
- Karanth KU, Nichols JD, Seidensticker J, Dinerstein E, Smith JLD, McDougal C, Johhnsingh, AJT, Chundawat, R, Thapar, V. Science deficiency in conservation practice: The monitoring of tiger populations in India. Anim Conserv. 2003;6: 141–146.
- Karanth KU. India’s Tiger Counts: The Long March to Reliable Science. Econ Polit Weekly. 2011;XLVI: 22–25.
- Gopalaswamy AM, Delampady M, Karanth KU, Kumar NS, Macdonald DW. An examination of index-calibration experiments: counting tigers at macroecological scales. Yoccoz N, editor. Methods Ecol Evol. 2015;6: 1055–1066. doi:10.1111/2041-210X.12351