DOI: 10.5281/zenodo.7003124
title: Data for: Four decades of phenology in an alpine amphibian: trends, stasis, and climatic drivers

description: This dataset is used for the analysis of the breeding phenology of a common toad (Bufo bufo) alpine population, and how it is associated with either climatic conditions or the genetics of the population.

 

Toad Data

Since 1982, we have captured annually all the toads that come to breed at the study pond. We then marked (first by toe-clipping, then starting in 1993 by implanting PIT tags), measured, and released them in the same place (Hemelaar, 1988; Grossenbacher, 2002). To make sure we captured both early and late arrivers, we repeated this procedure for on average 5–6 nights, with breaks in-between of about 2-4 days (i.e, the data conform to Pollock’s (1982) robust design). The length of the field work period usually covers the breeding season duration, which typically lasts about two weeks at our study pond. This design also had the advantage of not overly stressing the toads. In total, for the period 1982–2020, 3053 uniquely recognizable individuals have been caught, of which 1852 were males and 1201 females. For each individual we have a record of presence for each capture night over the study period. Given the reduced size of the pond and the repeated capture rounds within a capture night, we assumed high capture probabilities (capture probability p ≈ 0.85 per year based on a preliminary analysis of the mark-recapture data). At the population level we determined for each year a start, a peak, and an end date of breeding (i.e., first capture night, the capture night when most toads were captured, and last capture night, respectively). These calendar dates were all transformed into days of the year (where January 1st is 1), to facilitate modelling of long-term trends.

 

Weather Data

We obtained climatic data for the period 1980–2020 from the DaymetCH dataset (data obtained from Bioclimatic maps of Switzerland © WSL, based on station data from the Federal Office of Meteorology and Climatology MeteoSwiss, and elaborated by the Land Change Science group, WSL). This dataset consists of a 100-metre resolution grid of interpolated estimates of weather variables, using meteorological data from ground stations and the Daymet software (Thornton et al., 1997). We obtained data for the cell containing the breeding pond for the following variables: daily minimum, maximum, and mean temperature, daily total precipitation, and daily snow water equivalent (SWE; the equivalent amount of water stored in the snow pack). We then calculated average seasonal minimum daily temperatures (winter and spring), and cumulative seasonal precipitation (spring) and SWE (winter and spring). The csv file Season_values store these measures (one value for each of the 5 climatic variables per year, for the period 1982-2020, as the study on the toads started in 1982).

We conducted all the analyses in R (R version 4.1.1; R Core Team, 2020) with RStudio (version 2022.7.1.554; R Studio Team, 2022).
description: This project was funded by the Federal Office for the Environment (contract numbers: 20.0001.PJ/46DBED0F1 and 06.0126-PZ Artenförderung / N494-1379) and the Stiftung Temperatio.