Large-scale controls on the distribution and breeding ecology of the common frog (Rana temporaria) in an upland landscape

There is limited research regarding amphibian distribution and status in rural upland habitats in Britain. Previous studies suggest potential influences on distribution and abundance arising from habitat modification and acidification. However, the extent to which these factors influence distribution at the landscape level is unclear. This study aimed to evaluate whether particular features of the aquatic and terrestrial habitat influence distribution and breeding ecology of common frogs (Rana temporaria L.) in rural upland areas. In particular, the extent to which aquatic and early terrestrial life-stages might be impacted upon by the quality of their respective habitats was investigated. Common frogs were found to be widespread and ubiquitous throughout the study area. No evidence was found to suggest that any specific biotic or abiotic feature of either the aquatic or terrestrial habitat significantly influenced distribution and relative abundance of breeding adults. However, reproductive success was found to be significantly impacted upon by acidity in coniferous and hilltop habitats. It is probable that juvenile recruitment at some ponds is chronically reduced and populations are maintained through immigration. Recruitment in improved habitats was highly variable between ponds and between years, although it was not possible to elucidate precise controls on larval populations in the natural habitats studied. Significant differences in physical condition at metamorphosis among wild populations were demonstrated. This may signify possible differences in future growth, life-fitness and dispersal ability between populations, or at least between natal ponds. Dispersal by new juveniles is potentially affected by the vegetation structure surrounding breeding ponds. Intra- and interspecific differences in behaviour regarding microhabitat use were demonstrated. Rural upland habitats can be valuable habitats for amphibians and the common frog in particular. However, further research is required to better understand rates of recruitment and immigration and how terrestrial habitats mediate juvenile survival and dispersal