Improving the success of reinforcement programs: effects of a two-week confinement in a field enclosure on the anti-predator behaviour of captive-bred European hamsters.

Captive breeding programs are an important pillar in biodiversity conservation, aiming to prevent the extinction of threatened species. However, the establishment of self-sustaining populations in the wild through the release of captive-bred animals is often hampered by a high mortality upon release. In this study, we investigated how a 2-week confinement period within a large field enclosure affected the anti-predator behaviour of 'naive' captive-bred hamsters and how potential modifications persisted over time. During three consecutive tests, hamsters were confronted with a moving predator model (a red fox mount, Vulpes vulpes) and their behaviour was filmed. After the initial round of confrontation with the predator model, one group of hamsters (field group) was released into a field enclosure protected from predators, while the other group (control) remained in their individual laboratory cages. After 2 weeks, hamsters from the field group were recaptured and individuals of both groups underwent a second confrontation test. A total of 1 month after their return from the field enclosure, field hamsters were subjected to a last confrontation test. Video analysis, investigating four behavioural variables, revealed that field hamsters significantly modified their behavioural response following the 2 weeks confinement in the enclosure, while this was not the case for control hamsters. In addition, most behavioural modifications in field hamsters persisted over 1 month, while others started to revert. We suggest that an appropriate pre-release period inside a field enclosure will enable naive (captive-bred) hamsters to develop an adequate anti-predator behaviour that will increase their immediate survival probability upon release into the wild. We believe that such measure will be of great importance for hamster conservation programs.

Stormwater ponds as an amphibian breeding site: a case study with European green toad tadpoles.

Stormwater ponds (SWPs) are built to collect and retain polluted runoff water from roads. Consequently, they are not perceived as suitable habitat for wetland species, such as many amphibians. However, given the drastic decline of wetland areas, SWPs may serve as a habitat for protected amphibian species, such as the European green toad (Bufotes viridis). The latter species is frequently found inside these artificial ponds, but their reproductive success is unknown. We assessed the suitability of SWPs as breeding habitat for European green toads by monitoring 8 SWPs and 8 semi-natural ponds (SNPs), which served as control sites. At each site, two groups of 30 tadpoles, originating at that site, were held inside two floating enclosures that contained sediment from the respective pond. During bi-weekly monitoring, tadpoles were counted and measured, allowing to estimate growth and mortality rates. A variety of biotic and abiotic factors were studied to determine the causes of potential differences in growth and mortality rates between the two pond types. While growth rate did not differ between pond types, mortality rates were significantly greater in SWPs than in SNPs. The extremely low survival rate observed in SWPs might be explained by the considerably greater pollutant concentration in their sediment and/or by the presence of leeches, which were found exclusively inside SWPs. Implementation of management measures, such as regular draining/dredging during winter, might help to lower the pollutant concentration in the sediment and reduce the density of leeches inside SWPs, improving their suitability as habitat for amphibians.

A comparison of camera trap and permanent recording video camera efficiency in wildlife underpasses.

In the current context of biodiversity loss through habitat fragmentation, the effectiveness of wildlife crossings, installed at great expense as compensatory measures, is of vital importance for ecological and socio-economic actors. The evaluation of these structures is directly impacted by the efficiency of monitoring tools (camera traps…), which are used to assess the effectiveness of these crossings by observing the animals that use them. The aim of this study was to quantify the efficiency of camera traps in a wildlife crossing evaluation. Six permanent recording video systems sharing the same field of view as six Reconyx HC600 camera traps installed in three wildlife underpasses were used to assess the exact proportion of missed events (event being the presence of an animal within the field of view), and the error rate concerning underpass crossing behavior (defined as either Entry or Refusal). A sequence of photographs was triggered by either animals (true trigger) or artefacts (false trigger). We quantified the number of false triggers that had actually been caused by animals that were not visible on the images ("false" false triggers). Camera traps failed to record 43.6% of small mammal events (voles, mice, shrews, etc.) and 17% of medium-sized mammal events. The type of crossing behavior (Entry or Refusal) was incorrectly assessed in 40.1% of events, with a higher error rate for entries than for refusals. Among the 3.8% of false triggers, 85% of them were "false" false triggers. This study indicates a global underestimation of the effectiveness of wildlife crossings for small mammals. Means to improve the efficiency are discussed.