Spring temperature and land use change are associated withRana temporariareproductive success and phenology

Abstract

Chemical pollution, land cover change, and climate change have all been established as important drivers of amphibian reproductive success and phenology. However, little is known about the relative impacts of these anthropogenic stressors, nor how they may interact to alter amphibian population dynamics. Addressing this gap in our knowledge is important, as it allows us to identify and prioritise the most needed conservation actions. Here, we use long-term datasets to investigate landscape-scale drivers of variation in the reproductive success and phenology of UK Common frog (Rana temporaria) populations. Consistent with predictions, we found that increasing mean temperatures resulted in clear advancements in amphibian breeding phenology: earlier congregation of breeding R. temporaria, earlier initialisation of spawning, and earlier hatching. Temperature and number of frost days also affected rates of spawn mortality. However, temperature increases were also strongly correlated with increases in urban area, arable area, and nitrate levels in the vicinity of spawning grounds. None of these variables could explain variation in the total surface area of spawn present at breeding sites. These findings support previous work linking warming temperatures to shift in amphibian breeding phenology, but also highlight the importance of assessing the effect of land use change and pollution on wild amphibian populations. These results have implications for our understanding of the response of wild amphibian populations to climate change, and the management of human-dominated landscapes for declining wildlife populations.