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

爪印和虎的足迹同样是常用的虎数的方法。

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.

研人员用这些照片虎脚印的长度和宽度以及脚趾之间的角度，以及10种其他变确定不同虎的“身份”。