Automatic detection of small PIT-tagged animals using wildlife crossings

Abstract

Background: Mitigating the effect of linear transport infrastructure (LTI) on fauna is a crucial issue in road ecology. Wildlife crossing structures (tunnels or overpasses) are one solution that has been implemented to restore habitat connectivity and reduce wildlife mortality. Evaluating how these crossings function for small wildlife has often been recommended but, mainly due to technical limitations, is not often conducted in practice or only as short-term monitoring (less than 1 year). In this study, we developed and tested an automated device that records the detailed behaviour of animals when using wildlife tunnels. The method is based on marking and detecting individuals with RFID (radio-frequency identification) tags and allows small animals to be tracked. Composed of four antennas (detectors) placed at roughly 2 m intervals, the system was tested in a tunnel in northern France in the summer of 2017. One species of amphibian (the toad Bufo spinosus, n = 13) and two carabids (the ground beetles Carabus coriaceus and Carabus nemoralis, respectively, n = 3 and n = 4), marked beforehand with PIT (passive integrated transponder) tags, were recorded when they crossed these detectors. This allowed individual trajectories, including crossing speed, to be estimated. Results: We found that 12 of the 13 toads and 3 of the 7 ground beetles successfully crossed the entire wildlife passage of 7 m long. The detection rate of each detector varied from 8.33 to 100%, with a mean of 52.08%. All individuals were recorded by at least one detector. We observed high variability in the crossing characteristics of toads (mean transit duration = 41 min and 15 s ± 25 min) and ground beetles (6 h 11 min ± 3 h 30 min). The system provided information on precise trajectories (e.g., crossing speed, U-turns, distance travelled in the tunnel, proportion of individuals reaching the exit, etc.) for each individual, in a context of tunnel crossing. Conclusion: The system allowed us to record small animal behaviour in the context of tunnel crossing in which other types of tracking (e.g. radio-tracking) or detection (e.g. camera traps) are not effective. It also opens the possibility for a range of experiments that would contribute to a better understanding of the behaviour of small animals in tunnels, allowing a comparison of tunnel characteristics (such as size, building material, substrate, etc.) with the aim of increasing wildlife use of the tunnel and proposing guidelines for the construction and maintenance of these mitigation measures.

Improving trajectories of amphibians in wildlife passages

“…A monitoring system was designed, composed of four antennas (Biolog-id outdoor antennas, 100 × 8.5 × 2.5 cm), connected to an electronic control unit, described in detail in Testud et al (2019). Each antenna included an auto-tuning function and a rechargeable power battery.…”

“…A study has also shown that acoustic enrichment of tunnels with frog calls increased the speed and complete crossing rates of water frogs (Pelophylax esculentus) and the great crested newt (Triturus cristatus) (Testud et al, 2020). Individuals with PIT tags tracked by RFID antennas deployed in tunnels can give detailed information on movements inside the tunnel (Testud et al, 2019).…”

Methods of amphibian tracking

“…Метод активно використовують для оцінювання ефективності ренатуралізації видів [20], дослідження їхнього поширення, пошуку кормових біотопів і оцінювання їхнього використання, швидкості росту, виживання [59], денної активності й характеру руху особин різної статі [65], під час оцінювання використання підземних захисних бар'єрів [63], пошуку нерестилищ або місць гібернації [1], використання особиною території проживання [43], під час боротьби з нелегальною торгівлею тваринами [17] тощо.…”

Efficiency of aquatic PIT-tag telemetry, a powerful tool to improve monitoring and detection of marked individuals in pond environments

“…Radio-frequency identification (RFID) technology is of interest because electronic microchips using this technology (i.e., passive integrated transponder tags or PIT tags) do not require batteries or maintenance (Roberts, 2006;Want, 2006) and can be miniaturized. In ecology, these were first applied to fish (Prentice & Park, 1983) and then widely used to mark a plethora of taxa, including aquatic species, such as amphibians, for their identification and monitoring (Lucas & Baras, 2000;Roussel et al, 2000;Perret & Joly, 2002;Gibbons & Andrews, 2004;Schulte et al, 2007;Ferner, 2010;Testud et al, 2019). Several studies have concluded that this method has no detrimental effects on survival, growth, or body condition (Brown, 1997;Jehle & Hödl, 1998;Ott & Scott, 1999;Perret & Joly, 2002;Renet et al, 2021).…”