Toe-clipping has long been the benchmark method for individual marking of Amphibians, thanks to its efficiency and its limited cost, in spite of the physical damage inflicted on the animal. In smaller species, however, the removal of toes can affect behavior and reduce survival. Alternative techniques, such as the implant of subcutaneous tags and elastomers, are expensive and require expertise: their usage is therefore limited. 

The recent development of inexpensive, efficient and fast software for image recognition paved the way for a new, non-invasive paradigm of individual recognition, making use of individual variation in naturally occuring coloration patterns. Particularly interesting, in Hylids, is the lateral stripe, whose shape does not change throughout the life of tree frogs.

A paper that has recently been published in Acta herpetologica assesses the reliability of the software Hotspotter v. 1.0, tested for individual identification of adult Hyla arborea based on their lateral stripes. To this end,the authors captured 258 tree frogs in a pond in South-Western Bulgaria, and individually photographed them laterally. 

After comparing the results of the Hotspotter algorithm with a careful manual verification of each photograph, the authors confirmed that the lateral stripe is a reliable character for individual identification in the Common tree frog, and that the  tested software performs efficiently in photo identification. They underline, however, that the validity of the method is proven only for short term studies. The reliability of the Hotspotter software in long term population studies still needs to be verified.

Click here to read the full paper.

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