A method for marking individual animals in motion-triggered camera studies

Observing and collecting data on wildlife through motion-triggered cameras is becoming a widespread practice in ecological field research. To answer several ecological questions, including obtaining estimates of animal density, there is often the need to reliably identify individual animals in photos, which can be difficult, particularly at night. We created unique barcode patterns using heat shrink (a material that reflects infrared light from motion-triggered cameras) and attached these patterns on the antennae of very high frequency (VHF) collars on snowshoe hares, and on global positioning system (GPS) collars and coloured ear tags deployed on Canada lynx. This method resulted in highly accurate identification of individuals from motion-triggered camera photos, even when the majority of photos were taken at night. The marking method described here is a methodological innovation that allows impartial and reliable identification at any time of day and can be used on a variety of different species and for a range of research applications.