Identification of individual leopards (Panthera pardus kotiya) using spot pattern variation

Twenty‐one captive leopards Panthera pardus kotiya at the National Zoological Gardens in Sri Lanka were individually identified using spot pattern variation, Based on an identification method established for lions (Panthera leo), a code was devised examining 23 variable characters, each of which had one to three values. These characters ranged from number and spacing of muzzle spots to forehead and eye patterns. Correlation among characters to be used for identification was minimized using principal component cluster analysis. The most variable character was chosen from each of eight non‐overlapping clusters, and frequencies were calculated for each character value. The probability of occurrence of a given spot pattern was calculated as the sum of the frequencies of each character value. From this probability of occurrence, the information content, in bits, was computed for each pattern. The number of bits per character was also calculated. Using the binomial theorem, the reliability of identification was estimated as the sum of the probabilities of zero or one individual having an identical combination of character values. These binomial probabilities exceeded 0.99 for 15 out of 21 animals, and 0.95 for all but two. In these two animals, the information content was low (5.99 and 5.50 bits, respectively) compared to the others, in which information content ranged from 6.87–10.86. Although the mean number of bits (8.5) was theoretically sufficient for a 99% reliable identification, it was concluded that supplementation with an additional character would be worthwhile for identification of individual leopards.