When Do Peepers Peep? Climate, and the Date of First Calling in the Spring Peeper (Pseudacris crucifer) in Southeastern New York State.

The date of first calling (DFC) of Pseudacris crucifer (Spring Peeper) was recorded over 15 years between 1997 and 2012 in a small vernal pond in southeastern New York State. There was no statistically significant trend in temperature or in the DFC over this period. To determine what temperature cues best predicted DFC, 20 potential temperature indices (daily mean, minimum and maximum temperatures averaged over several different time periods, and thermal sums using several different base temperatures) and five precipitation indices (precipitation on the DFC and for four time windows prior to the DFC) were calculated, and predicted DFCs were compared to observed DFCs. The thermal sum with a base of 3 °C (TS3) was the best predictor but overestimated DFC slightly at high values of DFC. In evaluating impacts of climate change on the calling of this frog, the TS3 index may provide a more accurate metric than the daily temperature statistics that have been used in previous studies. In a 63-year record from a nearby weather station, the TS3 index declined significantly, suggesting that Spring Peepers may be calling earlier now than they were in the mid-2Oth century. [ABSTRACT FROM AUTHOR]