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20 December 2023 Environmental Predictors of the Onset of Spawning Migration in Pelobates vespertinus (Anura: Pelobatidae)
Mikhail V. Yermokhin, Vasily G. Tabachishin
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The dates of the onset of spawning migrations of local populations of Pelobates vespertinus (the Pallas spadefoot toad) in the Medveditsa river valley (Russia, Saratov Region) were determined in 2009–2019. It was found that the minimum threshold value of the water temperature in every spawning water body corresponding to the arrival of first individuals of the species to their spawning area was 4.5°C. Moreover, according to the nearest weather station's long-term forecast of air temperature, the average daily water temperature at the spawning site was calculated, equal to the average daily air temperature over 10 d. By analyzing the dynamics of this indicator, the dates of a steady transition of water temperature through its threshold value (4.5°C) were calculated. This date was considered the predicted start date of P. vespertinus spawning migrations. Any deviation of the actual start date of spawning migrations from the predicted one did not exceed 3 d for 11 years. The lead time for predicting the actual start date of migrations is positively related to the water temperature increase rate. During the study period, the lead time of the forecast was 6–18 d (12 d on the average). Our historical reconstruction of the long-term dynamics of the water temperature increase rate from weather archives and the forecast lead time (according to a model describing their relationship) in 1892–2008 showed that these parameters had no significant intra-century trend against the background of global climate warming. Our proposed method for predicting the start date of spawning migrations can be recommended for use in planning any research on P. vespertinus populations, ecosystem processes, and species conservation measures.

Mikhail V. Yermokhin and Vasily G. Tabachishin "Environmental Predictors of the Onset of Spawning Migration in Pelobates vespertinus (Anura: Pelobatidae)," South American Journal of Herpetology 29(1), 18-26, (20 December 2023).
Received: 7 January 2021; Accepted: 6 April 2023; Published: 20 December 2023
Anuran amphibians
Forecast lead time
Temperature increase rate
Threshold water temperature
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