Print PageAmur tiger, a keystone species in Northeast Asia, has experienced dramatic population decline in the last century. Habitat losses, poaching, and deprivation of preys are believed to be main causes. Recent conservation measures have been implemented, but the effectiveness is still unclear. The density of tiger prey may serve as quantitative indicator for measuring those effects.
Rowcliffe et al.’s gas model (2008) was adopted to estimate the density of the two most popular tiger prey, Siberian roe deer (Capreolus pygargus) and wild boar (Sus scrofa). 27 infrared-triggered cameras have been set in an area (43.0°N~45.0°N, 130.5°E~131.5°E) near Sino-Russian border began from Sep. 2008. Present/Absent data were collected on the daily bases from photographs taken by each camera to run Rowcliffe’s model. Two main detective zone parameters (radius and angle) and two animal movement parameters (distance per day and group size) were systematically perturbed to show the possible ranges of density, and bootstrapping technique was used to estimate standard deviations caused by sampling stochasticity. The probable relationships between environmental factors and trapping rates of each camera-site were later explored.
Results/Conclusions
During the trapping period, 183 pictures of 13 species were photographed, including 71 independent events for roe deer and 19 for wild boar. The density was estimated to be 0.46(±0.80) individuals/km2 for roe deer, and 0.06(±0.25) for wild boar, when all parameters are in the best estimates. Variation in detective parameters (radius: 5-15 m, angle: 10°-30°) and animal movement distance (0.5-10 km/day for roe deer, 1-20 km/day for wild boar) may cause mean density varied from 6.51 (±11.38) to 0.09 (±0.19) individuals/km2 for the roe deer, and from 0.78 (±3.40) to 0.01 (±0.04) individuals/km2 for the wild boar. Group size appeared to be different in photos between summer and winter, and had influence on density estimation.
It can be concluded that using camera traps can achieve reasonable density estimations that were comparable with results of traditional surveys from former literatures. However, the sample size seems very insufficient to get stable estimations, and model parameters have great influences on density estimations. Not many significant relationships were found between trapping rate and environmental factors, probably due to small sample size resulting in insufficient statistics test power.
