This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Eleven years ago surveys estimated that about 440 Bengal tigers (Panthera tigris tigris) roamed the dense mangrove forests of Bangladesh’s Sundarbans region. Today we have a new number and it is much, much lower. According to preliminary results from the latest census, the Sundarbans only hold an estimated 106 tigers.
There are two major causes for the decline: First of all, tiger poaching—parts of the animals are used in traditional Asian medicine—is rampant. The Bangladesh Forest Department has records of 49 tigers killed between 2001 and 2014, although that is unlikely to include every tiger caught by poachers.
Secondly, the scientific methods used to count the tigers have improved. The new census, conducted in November 2013 and 2014, used infrared cameras and other camera traps to come up with much better data than we had before. The 2004 estimate was based on “pugmarks” (footprints), which biologists now say was an unreliable method for estimating population and may have inflated the previous number.
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The Bangladesh census comes hot on the heels of similar studies that revealed a 30 percent increase in India’s Bengal tiger population to more than 2,200—although that, too, used a different scientific method than previous counts. The last Indian tiger census, conducted in 2010, only counted cats on reserves and sanctuaries; the new one looked at all of the country’s tigers. Around the same time the estimated number of Amur or Siberian tigers (P. t. altaica) in Russia increased to between 480 and 540, up from 423 to 502 in 2005. (Both of these numbers, like those in Bangladesh, are also preliminary.)
Why do these new counts matter? All of the nations in which tigers currently live have pledged to double their cat populations by the year 2022, the next year of the tiger on the Chinese calendar. The first step toward meeting that goal is figuring out how many tigers we actually have. That’s challenging because tigers live solitary lives and spread out over enormous ranges where their natural camouflage allows them to blend into the environment. Bangladesh’s Sundarbans region alone stretches over more than 3,000 square kilometers and its dense mangroves provide extraordinary cover for tigers (although not good enough to hide them from poachers). Once we have that count, we can better understand how to protect them and further boost their numbers.
While all of this is going on, there’s also a new debate about tiger subspecies. A paper published last month in Science Advances argued that we need to stop counting tigers as nine separate subspecies (three of which are already extinct). The paper suggests we only recognize two tiger subspecies, one on mainland China and another from the islands of Sumatra, Bali and Java. The authors say this reclassification would allow conservationists to adopt new approaches to protect tigers by addressing them as two big groups instead of half a dozen little ones and dozens of disparate population clusters. The idea has yet to earn broad scientific consensus.
We’re likely to hear a lot more about these animals as we approach the year of the tiger. The Bangladesh count may appear to be bad news on the surface but at the same time it illustrates how much we’re learning and the steps many governments and organizations are taking to help prevent these big cats from disappearing altogether.
Photo by Koshy Koshy. Used under Creative Commons license