Information on abundance and variation in abundance are bases for the effective wildlife management. Accurate survey methods are necessary to monitor the status and dynamics of endangered population of Amur tiger. The tigers are notoriously hard to monitor because they are secretive, occur at low density, wander widely, and are very rarely observed. Suitable monitoring methods vary in their reliability depending on the monitoring objectives, the spatial and temporal scale, tiger population density, prey density, climate, terrain and other environmental parameters.
The accuracy and feasibility of three methods (Information collecting networks, traditional transect survey and tiger-prey biomass relationships) for monitoring Amur tiger population abundance were assessed in the eastern Wanda Mountains, Heilongjiang Province and 8 bordering forest area between the southern Laoye Mountains in Heilongjiang Province and the northern Dalong Mountains in Jilin province during 2002-2011.The results showed that: 1) there were at least 6-9 wild Amur tiger in the eastern Wanda Mountains (1 male, 2-3 adult females, 2-4 sub-adults and 1 cub), in 2006 by using an information network for tigers; 2) there were 22-27 wild tigers in the eastern Wanda Mountains in 2002-2004 based on the prey biomass relationship method, which obviously exaggerated the tiger population size; and 3) 0 tigers in 8 bordering forestry areas between the southern Laoye mountains in Heilongjiang Province and the northern Dalong Mountains in Jilin province, in 2011 by using traditional transect method, which underestimated the true tiger population size.
The reasons for exaggeration of the tiger population using the biomass method could be previous losses of tigers from the area due to snares and competition with another carnivore, especially with people for ungulates. The transect method may have underestimated tiger densities in the survey areas because it was based on little prior knowledge of tiger behavior. It could only be usefully applied when tigers exist in at least moderate densities (i.e., when there is a high probability of encountering tiger tracks along a suite of routes). Although there is inherent potential error and bias, such as the unclear relationships of "expert estimates" and the true density, and between tiger track densities and actual tiger densities, same as the transect method, the monitoring of tiger populations using information networks provides a record of minimum tiger presence, and may be an appropriate approach when tiger presence is extremely rare, transitory and unstable, such as in northeast China. This approach is economically efficient and should be further improved by established a wider network across the landscape to encompass all potential tiger habitat using better trained monitoring staff.
An occupancy survey would be an ideal method to monitor tigers at the landscape scale when tigers are determined to be permanently present in some areas of northeastern China. Camera traps, DNA identification, dog identification, track identification, monitoring methodology based on capture-recapture systems may only work when tiger densities are high enough to provide ample capture-recapture data. They may be appropriate for future use in China. The density overestimates as determined by the large ungulate biomass method indicated that tiger numbers might be stabilized if strict measures were taken to alleviate the factors threating both the tigers and their prey. We should also monitor populations of large ungulates and threat factors to those ungulates while at the same time make efforts to monitor abundance trends in the tiger population itself.