Are ear notches an effective tool for monitoring individual rhino?
Notching of rhino ears is a common method for distinguishing free-ranging individuals, as the species often lacks unique marks or patterns. However, there are no data available on the reliability of rhino identification using this method. We conducted a field study with 107 participants at the Southern African Wildlife College to test the visibility of different ear notch positions from five distance points in bush and open habitats. Results show that correct identification rates at 20 m between observer and rhino were only 6 % in the bush and 23 % in the open habitat. Without the use of binoculars, no correct identification was seen at 30 m distance in the bush and at 65 m in the open habitat. The notching positions we tested differed in terms of accuracy of detection. This allowed us to draw conclusions about which positions should be favoured to optimise identification. Relationships between recorded observer skills, environmental factors, the use of binoculars, and rate of successful identification of ear notches were tested by using generalized linear models. The outcomes of this study suggest that ear notching alone does not allow for reliable identification of rhino individuals from even relatively short distances. We recommend that other artificial marking methods and natural distinguishing marks should be investigated further and could be combined with modern tracking technologies.