Can road stormwater ponds be successfully exploited by the European green frog (Pelophylax sp.)?

Stormwater ponds (“SWPs”) are artificial roadside structures, conceived to retain and clean polluted runoff water, before its release to the environment. SWPs were not designed as suitable habitats for wildlife. However, SWPs in Europe are frequently used as breeding sites by amphibians, especially by the European green frog ( Pelophylax sp. ). Yet, the potential long-term effects of pollutants within SWPs on the populations of this species are unknown. In this study, we investigated the suitability of SWPs as a habitat for European green frogs living in Alsace, NE France, a region with a highly modified landscape that mainly consists of croplands with few natural wetlands remaining. We compared various biological indicators of individual health in 709 green frogs belonging to different life history stages, living in 9 semi-natural ponds (SNPs) and in 25 SWPs. There were no differences between these two pond types for most of the indicators investigated. However, juveniles had a lower body condition (−124%) in SWPs, while adults were 8.3% larger and 41.4% heavier in SWPs. Based on these results, we suggest that SWPs are not a suitable habitat for the development of European green frogs (i.e. juveniles), but may serve as a substitute habitat for adults in a highly modified landscape with few natural wetlands remaining. SWPs may especially act as relay sites, allowing frogs to colonize relict wetlands.