Using radio-frequency identification technology to monitor Eurasian beavers

The use of radio-frequency identification (RFID) offers new potential in remote wildlife monitoring to reduce the invasive nature of studies requiring direct contact with study animals. Facilitated by the emergence of new technology, RFID can remotely identify individual animals implanted with passive-integrated-transponder (PIT) tags. We aimed to establish and assess a new technique for remote RFID for remotely and noninvasively monitoring a wild population of a semi-aquatic mammal, the Eurasian beaver (Castor fiber). A fixed reader was installed from June 2018 to July 2019 at beaver lodges within the territories of 8 family-groups in Vestfold and Telemark, Norway, for 3 nights per lodge, with RFID antennas at lodge entrances. Microchipped beavers were detected when entering or leaving the lodge. The family-group size recorded using RFID was compared to the known family-group size based on live capture records and direct observations. The family-group size recorded using RFID was smaller than the known family-group size. However, testing suggested that individuals inhabiting a lodge with a fixed reader installed had a high probability of detection (98.44. Fixed readers are effective where the identification of individuals at a focal point is appropriate, with unique applications for monitoring species with high fidelity to lodges or dens, or species that exhibit central-place foraging behavior. Research using RFID through fixed PIT tag readers should be given priority for noninvasive beaver population monitoring. Whereas fixed PIT tag readers may not record entire beaver family-groups, they provide an accurate and efficient alternative to other monitoring techniques.