From March through May 2010 WCS conducted a survey of tigers using camera trapping in Khabarovsk Province of the Russian Far East in a portion of the Khor River Basin. This region is one of one of 16 monitoring units where annual assessments of trends in the population of Amur tigers, their prey and their habitat have been ongoing since 1997. This work is part of a larger project to develop statistically robust methods for assessing the Amur tiger population. Currently, tiger numbers in Russia are estimated through winter surveys of tracks in the snow, a method that largely relies on expert judgment to interpret results. Camera-trapping allows us to make more statistically defensible estimates of tiger numbers, which we are then comparing with results of winter track surveys.
The “Khorsky model area” included 1300 km2 of multiple-use lands at the northern end of Amur tiger range. We took a total of 21 photos of 5 different tigers, including 3 males, 1 female and 1 unidentified individual. After analyzing our data we were able to estimate the tiger density at this site at 0.6 individuals per 100 km2.
In comparison, experts interpreting the results of winter snow track surveys conducted in 2009-2010 estimated a total of 6 tigers living in the area (3 males and 3 females) and a population density of 0.5 individuals per 100 km2.
Thus both survey methods provided similar estimates of tiger numbers in this area. But that has not always been the case: in Sikhote-Alin Biosphere Reserve, for example, the results of camera-trapping and winter track surveys have differed by as much as a factor of 2 in some years. We believe that the success we achieved in obtaining similar results this year at the Khorsky model area is probably due to the small time interval between winter track surveys and camera-trapping: camera-trapping began almost immediately after the last snow surveys were completed. In Sikhote-Alin Reserve, in contrast, camera-trapping has mostly been conducted in the late spring through early fall. Our results emphasize the need to conduct both types of surveys simultaneously if we hope to improve Amur tiger monitoring methods.
At present almost all indicators of the status of the Amur tiger population are based upon best expert interpretation of the quantity and distribution of tracks in the snow, a method that is logistically convenient and cost-effective. However, thus far it has been impossible to evaluate the accuracy and precision of this method. Moreover, snow track surveys do not allow us to understand rates of population turnover (i.e., how often individuals in a population appear or disappear, which accounts for both mortalities and dispersal). The use of camera traps allows us to obtain more information about key indicators of population dynamics are objective, accurate, and statistically robust. We plan to continue our work at other monitoring units, and to clarify the relationship between results achieved through winter track surveys and camera-trap surveys. If there is a clear relationship between track surveys and camera trapping, we can use track surveys over large areas (because logistically and financially it is the easiest and cheapest method to employ) with camera trapping over smaller areas to provide rigor and define the precise relationship of tracks and tigers. Ultimately, we seek to develop a more objective, yet economically feasible, method for surveying the Amur tiger in the remote regions of the Russian Far East.