Allometry of scales in Chinese pangolins (Manis pentadactyla) and Malayan pangolins (Manis javanica) and application in judicial expertise

Pangolins are unique mammals in that they possess scales that serve a protective biological function. As an important raw material of traditional medicine, illegal trades of these scales are frequent and difficult to investigate or prosecute. We used allometric models of dry weight of scales to compare 35 Chinese pangolins (Manis pentadactyla) and 119 Malayan pangolins (Manis javanica). Our results showed that the dry weight of scales increases significantly faster with the length of head and body in Malayan pangolins (P=0.005), while dry weight of scales is positive (slope=3.725) in Malayan pangolins but isometric (slope=3.105) in Chinese pangolins. The differences in morphology between these species may reflect an evolutionary adaptation to different environments; Malayan pangolins in tropical regions appear to suffer from greater predation pressure than Chinese pangolins in temperate regions. We advise the conversion standards between dry weight of scales and number of individuals as 573.47 g in Chinese pangolins and 360.51 g in Malayan pangolins respectively, and when two are mixed together, average above two parameters of the median at 466.99 g. We propose these measurements be used as judicial evidences in forensic identification of related cases.