An anti-predation device to facilitate and secure the crossing of small mammals in motorway wildlife underpasses. (II) Validation with the European hamster under semi-natural conditions

•A sub-tunnel to secure the crossing of small mammals throughout underpasses.•Validation of an anti-predation device with the endangered common hamster.•A device improving male hamsters crossing under predation risk. Increased predation risk or avoidance of wildlife underpasses by small mammals have been highlighted. To overcome this problem and to provide these species with an opportunity to safely cross road-crossing structures, we previously designed an Anti-Predation Tube (APT). The features (shape and size) of this device have been tested under laboratory conditions and its use by captive European hamsters (Cricetus cricetus) has been validated. In this study, we investigate both the enrichment and anti-predation functions of the APT for hamsters in an actual underpass. To do so, we built two small enclosures of 6 m2 at both extremities of an underpass and cross-manipulated the presence of the APT and a predator of hamsters, the European ferret. Our results show that the APT does not act as an enrichment, as it did not increase the crossing frequency of hamsters in the absence of the predator. However, it acts as an anti-predation device, since, in the presence of the ferret, male hamsters crossed more than 10 times as much when the APT was present inside the underpass than when it was not. We therefore recommend implementing the APT as a conservation measure to upgrade wildlife underpasses while conducting surveys to investigate how the presence of the APT influences the crossing of other small mammals and wildlife.