How many Western gorillas are there?

The honest answer to this question is that we really don't know. Since the mid-1990's, the figure of 100,000 Western gorillas has often been bandied about with great confidence. But this number is a fabrication: little more than a guess made in a way that violates virtually every basic principle of statistical estimation. This guess was not based on extensive survey data or a valid statistical methodology. It simply took population density estimates made in a couple of protected areas (parks and reserves) with uncharacteristically high gorilla densities and extrapolated them over a huge area spanning eight countries. Even the methodologies on which the original protected area estimates were made are suspect. In truth, we don't know how many Western gorillas there are, but all indications point to a number substantially less than 100,000. How much less? We just don't know.

What do we know?

Most of what we do know about the current abundance of Western gorillas comes from surveys conducted in protected areas (parks and other wildlife reserves) over the last five years. These surveys show that although there are still substantial populations of gorillas in a number of remote protected areas, these populations are showing signs of serious impact from hunting. In particular, gorilla population densities near the edges of protected areas, along roads, and near human settlements, logging camps, and petroleum extraction facilities tend to be much lower than in the middle of protected areas. What is going on outside of protected areas, where the bulk of Western gorillas are still assumed to live, is very poorly documented. But what little data do exist are alarming. Areas that housed large and healthy gorilla populations as recently as ten years ago (and that many members of the conservation community assume to still hold substantial populations) now appear to be largely empty of gorillas. After a ramping up of law enforcement effort, a regionwide survey to assess the magnitude of the population decline and the current population distribution is the second highest immediate priority for Western gorilla conservation. Such a survey would not be cheap. It would probably cost something on the order of $500,000-$1,000,000: roughly the same quantity that is regularly spent on international conservation meetings. But until such a survey is conducted, we run a serious risk of losing most Western gorillas before we even realize it.