Abstract
Habitat fragmentation is one of the drivers for amphibian population declines globally. Especially in industrialized countries roads disrupt the seasonal migration of amphibians between hibernation and reproduction sites, often ending in roadkills. Thus, a timely installing of temporary mitigation measures is important for amphibian conservation. We wanted to find out if plant phenology can be a proxy in advance to determine the start of amphibian migration, since both phenomena are triggered by temperature. We analysed data of 3751 amphibian and 7818 plant phenology observations from citizen science projects in Austria between 2000 and 2018. Using robust regression modelling we compared the migration of common toads (Bufo bufo) and common frogs (Rana temporaria) with the phenology of five tree, one shrub, and one herb species. Results showed close associations between the migration of common frogs and phenological phases of European larch, goat willow and apricot. Models based on goat willow predict migration of common frog to occur 21 days after flowering, when flowering was observed on 60th day of year; apricot based models predict migration to occur 1 day after flowering, observed on the 75th day of year. Common toads showed weaker associations with plant phenology than common frogs. Our findings suggest that plant phenology can be used to determine the onset of temporary mitigation measures for certain amphibian species to prevent roadkills.
Highlights
Preceding migration[20] or with average temperatures in March[21] or April[22]
We determined the phenological phases of amphibians and plants for the years 2000–2018 in three different climatic regions of Austria referred to as warm, moderate and cool region (Supplementary Tables S1 and S2, Supplementary Fig. S1)
Migrations of common toads and common frogs were observed across a time span of 37 days; earliest record of common frogs was on February, 27th 2008 (58th day of the year) and the latest record was on April, 5th 2006 (95th day of the year; Fig. 1)
Summary
Preceding migration[20] or with average temperatures in March[21] or April[22]. Similar findings are known for common frog with spawning dates correlating with air temperature in winter and early s pring[21] or the temperature sum in February and March[12]. Temperature is found to be the main driver of amphibian phenology, while the impact of precipitation is considered w eak[24] Another phenomenon that is mainly influenced by temperature (and daylength) is plant phenology including bud break, leaf unfolding or flowering[25,26,27]. Indications on the start of amphibian migration could be especially helpful for volunteers in nature conservation with limited experience and for regions without observational values yet, in order to timely install temporary amphibian mitigation measures Such an approach would be advantageous for amphibian conservation associations as monitoring plant phenological phases is easy to conduct and data on phenological phases are usually available[2,29]. We used robust regression models to test whether we can predict the onset of amphibian migration with plant phenology
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