Amphibian-Friendly Water Drainages for Agricultural Landscapes, Based on Multiple Species Surveys and Behavioural Trials for Pelophylax nigromaculatus

Amphibians are the most threatened vertebrate group on earth, and one of the reasons for their decline is habitat loss. While some populations have persisted in agricultural wetlands such as rice paddies, the current anthropisation of landscapes is dealing a new blow to the survival of these species. In rice paddies, the new threats are especially visible through the increased channelization of water bodies with increasingly efficient drainage ditches, which become deadly traps. We first conducted surveys over three years to determine the use of ditches by frog species for natural versus concrete ditches, and thus relate to habitat adequacy as well as the probability of becoming trapped in concrete ditches. We then set up four types of experimental arena for escape trials. Experiments were replicated for the Black-spotted pond frog (Pelophylax nigromaculatus), as a proxy for other species abundant in rice paddies in the Republic of Korea. We determined that a slope of at least 70 degrees, with engraved patterns, was the only set-up from which frogs managed to escape. We recommend the implementation of this type of device in areas where a high concentration of animals is trapped, before phasing out the ancient design and relying on amphibian-friendly drainage ditches as they also support higher amphibian biodiversity.