Comparison of methods to estimate the size of Indian pangolin (Manis crassicaudata) scale seizures using species-specific conversion parameters

Abstract

The absence of robust species-specific methods to estimate the number of animals in seizures of pangolin scales is a major barrier to effective law enforcement. Therefore, studies focused on developing methods to establish accurate conversion parameters are a priority. This study proposes improved methods to estimate the number of pangolins in the illegal trade to inform law-enforcing authorities. Based on the observations of 25 specimens, Indian pangolins were on average found to possess 511 scales. Three morph-types of scales were identified: broad rhombic (n=411), elongated kite shape (n=69), and folded scales (n=31). The mean dry weight of the three-scale morph-types was 7.5 g, 4.9 g, and 6.2 g. Based on the average frequency and mean dry weight of each scale morph type, the species-specific dry weight of scales for Indian pangolins was 3.6 kg. Accordingly, we propose new and improved methods based on scale morph-type frequencies and species-specific dry weight of scales to estimate the number of Indian pangolins from quantities of scales. Their accuracy was compared with current methods, and the improved methods were found to be more accurate.