The amphibian fingerprint: variability and identification from abdominal skin color patterns in túngara frogs (Engystomops pustulosus)

The color patterning of skin, feathers, or fur is often variable among animals and can potentially be used for individual identification and estimation of the genetic variability in the population. Effective identification systems are necessary in colonies of captive animals to create a pedigree and track the life history of each individual. Life history information can include health, mating, weight, length, and experimentation history. The goal of this study is to evaluate the effectiveness of ventral color pattern imaging for individual identification of túngara frogs (Engystomops pustulosus). We photographed the ventral skin of all the adult individuals in a captive population with \u3e 100 animals and delimited a polygon containing the abdomen for analysis in each photograph. Túngara frogs present a highly variable pattern of black spots on a the white background of their abdominal skin. The black spots vary in size, shape, connectivity, and color. We compared new images of a focal individual against images from every animal in the colony and computed a similarity index between each pair of images. Our preliminary results indicate that identification is invariably correct within our population. The focal image has a similarity index at least one order of magnitude higher for images of the closest matching individual than from images of other individuals in the population. Color pattern variation can be the basis of a low-cost, fast assessment, non-invasive system for individual identification. It can also allow for assessment of variability within a population of túngara frogs and possibly populations of other species