Paw print, or pugmark, tracing is another common technique for counting tigers.

爪老足迹同样是常用计算老数量方法。

The researchers then use the pictures to measure the length and width of each pugmark, the angle between toes, and 10 other variables to establish an ID.

研究人员用这些照片来测量老宽以及趾之间角，以及10种其他变量来确定不同老“身份”。