Tracking the Amur tiger of China-Russia borderlands

Background/Question/Methods Amur tiger (Panthera tigris altaica), the largest tiger subspecies, is the keystone species and the top predator in the mixed broadleaf and Korean pine (Pinus koraiensis) forest ecosystem in northeastern Asia, while tiger is categrized as an endangered species by IUCN red list. Most of Amur tiger’s habitat and population were lost in past century. Currently, there are 400­500 individuals in total, mostly distributed in Russia with a few in China. To conserve tiger in China with appropriate actions, it is crucial to have an accurate evaluation of the Amur tiger population in northeastern China.

We analyzed data taken by  87 camera traps from the surveys conducted in Hunchun Nature Reserve (1,222 km²) across China-Russia borderlands. Population size of tiger was estimated by using spatially explicit capture-recapture (SECR) model based on maximum likelihood estimation and Bayesian estimation with an data augmentation framework. The two estimation values were then compared and discussed. We also applied the non-spatial capture recapture model to estimate tiger population size and further analyzed the population density with an ad hoc estimation of the effective trapping area.

Results/Conclusions The non-spatial model estimation of tiger population in Hunchun Nature Reserve has 11-12.5 individuals, and its population density is 0.32 individuals/100 km², while the SECR models estimation of tiger population density is 0.23 to 0.30 individuals/100 km². The density estimated by the SECR models is smaller than the estimates of non-spatial model. We recommended SECR model because the spatially explicit method can avoid the bias resulting from an informal estimation to the effective survey area. The pixelated density map based on Bayesian model illustrated high density of tiger along the China-Russia border, especially in the mid-section. Different from the previous speculation that recent occurrence of Amur tiger in China are dispersing transients on sporadic forays from Russia, we documented the successful breeding and frequent territory-marking behaviors of Amur tiger in Hunchun Nature Reserve, indicating the residency of adult Amur tiger within China. This population will be the key source of tiger population recoveryin China. We outlined the importance of maintaining the cross-border connectivity for long-term conservation of the binational population of Amur tiger across the China-Russia borderlands.