A theory of spawning habitat selection in anurans

Abstract

Field and experimental evidence shows that anuran adults selecting spawning habitats make flexible, context-dependent choices based on multiple biotic and abiotic factors. Despite the empirical evidence, few formal theories explain the context-dependent selection of spawning habitats by anurans. To fill this gap, we develop a mathematical model to analyze the interacting effects of multiple biotic and abiotic factors on anuran spawning habitat selection. Our model considers the effects of habitat quality (e.g., resource levels, heterospecific predator abundances, and other abiotic conditions), spawning timing within a reproductive season, strength of conspecific competition among juveniles, and strength of conspecific predation of early hatching on late hatching juveniles. The model predicts that while early-spawning adults generally favor better-quality habitats, late-spawning adults may not necessarily prefer better-quality habitats. Predation of late-hatching juveniles by early-hatching juveniles promotes the avoidance of better-quality habitats by late-spawning adults. Stronger competition among juveniles of the same developmental age increases the preference of late-spawning adults toward better-quality habitats. These predictions are in broad agreement with empirical evidence. Our model demonstrates that the tension between habitat quality and negative conspecific interactions among juveniles drives the context-dependent selection of spawning habitats by anuran adults.