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

爪虎的足迹同样是常用的计算虎数量的方法。

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.

研人员用这些照片来测量虎的长度宽度趾之间的角度，10种其他变量来确定不同虎的“身份”。