Geeky geckos: Using photography and a software package to identify individuals of Woodworthia brunnea

Abstract

Understanding basic life-history parameters of a population and obtaining accurate estimates of population size are essential to making evidenced-based decisions regarding conservation strategies. Estimating population size and characterizing life-history parameters can be effected using mark-recapture studies, which necessitate the ability to recognize individuals. To date, no methodology has been developed for using photography to identify individuals of Woodworthia brunnea. The aim of this project was (1) to develop an effective photographic method for identifying individuals of W. brunnea, and (2) to apply our new methodology to the second year of an ongoing lizard monitoring project on Banks Peninsula. Using Orana Wildlife Park’s captive population of Woodworthia geckos, we developed our photography techniques and tested the effectiveness of the computer programme I3S Pattern in identifying individual geckos. We then conducted three rounds of lizard monitoring at 17 sites across Banks Peninsula from December 2022 – May 2023, photographing each gecko found in our lizard lodges and identifying recaptured individuals in our second and third rounds of monitoring. We found that iris photographs provided more accurate individual identifications than did dorsal photographs using I3S Pattern, but that the accuracy of identifications varies with photograph quality. We also found that dorsal photographs are effective within a field season at confirming identifications made by I3S Pattern. We do not recommend using dorsal photographs alone between field seasons because data from Orana Wildlife Park’s geckos demonstrated that dorsal patterns can fade significantly over five years. Future work will determine how stable iris patterns are over time.