The Effects of Temperature and Precipitation on the Breeding Migration of the Spotted Salamander (Ambystoma maculatum)

Abstract

We examined and quantified the roles of air temperature, soil temperature and precipitation as potential correlates of breeding immigration for a population of spotted salamanders in western St. Louis County, Missouri, for 10 yr. Mean 3 d air temperature provided the best temperature predictor of salamander immigration, significantly explaining 41% of the variation in the number of immigrating salamanders up to the modal class. There was no relationship between the level of immigration and the amount of precipitation recorded over a 24 h period spanning the movement of salamanders. We describe favorable conditions of rainfall (4 mm) and mean 3 d temperature (5.5 C) above which 98.3% of all imigration occurred. After the first week of Feb., all days with these threshold values showed some level of immigration. Salamanders did not immigrate during Dec. or Jan. despite instances of above threshold temperature and precipitation. Male salamanders typically are represented in greater frequency than females early in the immigration season. This difference appears to be due to a differential response of the sexes to temperature. Salamander immigration was significantly correlated with soil temperature at 30 cm below the surface. Most immigration occurred when the soil temperature at 30 cm was at least 4.5 C and the thermal profile was reversed (the surface was warmer than the soil at 30 cm). This threshold system of cues may reduce the likelihood that immigrating salamanders will be incapacitated by sudden cold.