On the Reliability of Expert Identification of Small-Medium Sized Mammals from Camera Trap Photos

Camera trapping in scientific research has captivated practitioners globally and is now widely used as a primary survey method. Using photos to identify some species, especially coexisting small species of similar appearance and niche is questionable and if incorrectly identified can lead to poor conservation and management outcomes. The aim of our investigation was to test how accurately mammalogists with expertise in mammal identification could identify a range of small-medium sized species recorded during camera trap surveys. This study presents the results of an Australian case study but the findings apply broadly and are relevant throughout the world's ecosystems. Using an internet survey, 58 questions were posed to assess practitioner expertise in mammal trapping, and their accuracy in identifying 21 photos of 10 small-medium sized Australian mammal species. Particular focus was placed on the identification of the rare and threatened Hastings River Mouse (Pseudomys oralis) but other rodent species such as the Black Rat (Rattus rattus), the Bush Rat (Rattus fuscipes), and the Swamp Rat (Rattus lutreolus) were included. The survey indicated that the correct identification of some small mammals, in particular rodents, is highly variable between images of the same species, and that as a whole the professional wildlife community performs poorly at the identification of such species. Identification was more accurate where species were less likely to be confused with similar looking species, or where their identification was simple and/or obvious. Accurate identification of small-medium sized mammals, in particular rodents using camera trap imagery is difficult and this study highlights the potential discrepancies that may arise in wildlife research. Robust methods to assist in minimising errors and bias of animal identification need to be explored. In circumstances where similar looking species coexist, or in species rich ecosystems, a reliance on camera trapping alone may lead to mistaken identity.