How to Count Tigers

By John Goodrich, Ph.D.
Chief Scientist


Recent claims that global numbers of wild tigers are increasing are puzzling. Tiger numbers have increased in a handful of sites — the Western Ghats in India, Chitwan in Nepal, and perhaps Huai Kha Khaeng in Thailand, to name a few. In these places, where governments are committed to delivering rigorous protection, as well as conducting comprehensive, science-based surveys, tiger recovery is happening, and there is data to prove it.

But, it is important to put these small victories into context. While it’s great news that the current data suggest there are more tigers in the wild than we thought previously, there is no scientific evidence of a global population increase—in most tiger sites, we’re just doing a better job of counting them.

Thanks to improved camera trap technology, the cooperation of governments, and more boots on the ground counting tigers across more of their range, we have progressed over the past 15 years from making educated guesses about the number of tigers to making statistically sound estimates, at least in some areas. To wit, in 1999, global tiger numbers were estimated to be between five and seven thousand; in 2010, the estimate was 3,200. The numbers released last week estimate around 3,900 tigers left in the wild. Good news, but not proof of an increase from 2010. Here’s why:

While the methodology for counting tigers is now well established, it's important to note that scientifically valid, countrywide studies have only been carried out in a handful of countries. And, the extent and the quality of the studies is highly variable from year to year and within countries, as well as from country to country, making it very difficult to make conclusive statements about the total number of wild tigers in the world today, let alone claims of increases.

Further, even when there are good scientific studies, the results are not always interpreted correctly. Let’s say you go into a donut shop, count the donuts on half the shelves and conclude there are 100 donuts in the shop. The next day you go in and count the donuts on all the shelves in the shop and come up with a total of 200 donuts. Would it be accurate to conclude that the number of donuts had increased by 100 from one day to the next?

Complicating matters is that comprehensive population studies are incredibly difficult to implement because tigers inhabit some of the most dense, rugged, and difficult to access parts of the world. To extend the donut analogy, it’s as if donuts were stored in the most hard to reach places in the shop, like in the ductwork or under the floor. Trying to count tigers in every inch of their landscape is not logistically feasible and would be a waste of limited conservation resources.

It is possible to estimate tiger numbers by zeroing in on the world’s most important tiger populations—those in habitat patches large enough to produce surplus tigers over the long term—called source sites. This is the metric that we are using to track global tiger population change, while focusing on activities that not only ensure tigers survive in the wild long term, but that their numbers will increase. The metric is not an estimate of the total number of wild tigers in the world—that number will likely remain as elusive as the tiger itself—but rather the number of tigers in the world’s most important tiger sites. 

Within these source sites, tiger populations can be recovered by eliminating critical threats such as poaching, habitat loss and encroachment, and human-tiger conflict. In these smaller areas, tiger numbers can be estimated every year to evaluate success. This is the heart of Panthera’s Tigers Forever Program, which we are implementing in roughly 40 percent of the 42 known source sites.

By monitoring the world’s most important sites with the best available science, we can accurately track trends in tiger numbers. Most critically of all, by implementing world-class site security training and law enforcement at these sites, we can ensure that tiger numbers continue to increase, and tigers will thrive in the wild, forever.  

Editor's Note: This post was updated on April 19, 2016.