Déclin de la grenouille rousse (Rana temporaria) au Luxembourg sur la période 2010-2023

Decline of the common frog (Rana temporaria) in Luxembourg over the period 2010-2023. In Luxembourg, the common frog Rana temporaria (Linnaeus, 1758) is a species for which the Government is committed to reversing negative population trends by 2030. Monitoring efforts carried out in 246 ponds scattered across the country have enabled a quantitative assessment of their breeding population trends. A presence survey and a count of the number of clutches were conducted in March between 2010 and 2012 and again between 2021 and 2023. A comparative analysis of the two sampling periods reveals a significant decline of 39% in the number of occupied ponds and 38% in the number of clutches at the sampled ponds. Several land-cover variables were extracted at different spatial scales around the sampled ponds (in a radius of 100, 400 and 1000 meters). Our analyses indicated that low numbers of clutches were associated with arable land around ponds. It also showed that the number of common frog clutches remained stable or increased in ponds surrounded by large areas of forest and flood plains, whereas it decreased in ponds where there were fish. To reverse the decline of the common frog, the creation of new ponds near woodland is essential, but the management and restoration of the terrestrial habitat around wetlands is also important, especially in agricultural areas. The conservation of the common frog must be carried out not only locally, but also at the landscape level, in order to account for the connectivity and exchanges between populations.