Scute Patterns as an Individual Identification Tool in an American Crocodile (Crocodylus acutus) Population on Coiba Island, Panama

Identification of individuals based on morphological patterns is a strategy used primarily in human forensics that has also been applied successfully in several wildlife scenarios. To date, no study has evaluated the potential of these techniques on American Crocodiles (Crocodylus acutus). We assessed whether the dorsal scute number and pattern of 110 American Crocodiles captured from the wild on Coiba Island, Panama could be used for individual recognition. We estimated scute variation using the number and position of scutes, testing both a binary and a coded assessment for scute presence and pattern, respectively. We analyzed scute patterns using 21 transverse scute lines (TSL) including the three most prominent scutes present on each side of the vertebral column axis. We found significant differences in the number of scutes per TSL and longitudinal scute lines (LSL) by individual. Based on both the binary and coded analyses, we identified all American Crocodiles assessed at the individual level, using only the first 13 and 10 TSL, respectively, in an anterior-posterior direction. This gave us a minimum probability of ≤0.0003 based on the coded analysis and ≤2.02 × 10-5 based on the binary analysis to find pattern repetition (one out of 3,333 and one out of 49,504 American Crocodiles have the most-common scute pattern, respectively). Because the C. acutus total population of Coiba Island has been estimated as no more than 1,000 individuals, we could use this individual identification pattern recognition method (IIPR) to identify every American Crocodile inhabiting this island.