Breeding Pond Selection and Movement Patterns by Eastern Spadefoot Toads (Scaphiopus holbrookii) in Relation to Weather and Edaphic Conditions

Abstract

Eastern Spadefoot Toads (Scaphiopus holbrookii) require fish-free, isolated, ephemeral ponds for breeding but otherwise inhabit surrounding uplands, commonly xeric longleaf pine (Pinus palustris) and wiregrass (Aristida beyrichiana) ecosystem. Fire suppression in the Florida sandhills has the potential to alter upland and pond suitability through increased hardwood densities and resultant higher transpiration. In this paper, we explore breeding and metamorphic emigration movements in relation to weather, hydrological conditions of ponds, and surrounding upland matrices. We use nine years of data from continuous monitoring with drift fences and pitfall traps at eight ephemeral ponds in two upland matrices: regularly burned, savanna-like sandhills (N = 4), and hardwood-invaded sandhills (N = 4). Neither adult nor metamorph captures differed between ponds within the two upland matrices, suggesting that they are tolerant of upland heterogeneity created by fire frequency. Explosive breeding occurred during nine periods and in all seasons; adults were captured rarely otherwise. At the landscape-level, an interaction between rainfall and maximum change in barometric pressure were the top significant predictors of explosive breeding. At the pond-level, rainfall and the change in pond depth during the month prior to breeding were the top significant predictors of adult captures. Metamorphic emigrations occurred following transformation and usually were complete within a week regardless of rainfall levels. Movement by adults and metamorphs was directional, but mean directions of adult emigrations and immigrations did not always correspond. Our results suggest that spadefoot toads are highly adapted to breeding conditions and upland habitat heterogeneity created by weather patterns and fire frequency in Florida sandhills.