An experimental assessment of invertebrate/vertebrate predation: the interaction between wolf spiders (Gladicosa pulchra) and terrestrial salamanders (Ambystoma maculatum)

Abstract

A series of laboratory experiments were conducted to determine if adult wolf spiders Gladicosa pulchra were capable of acting as predators of juvenile spotted salamanders Ambystoma maculatum. Spiders preyed upon salamanders in two of 20 trials and attacked salamanders in five trials. As attacks did not always kill salamanders, multiple attacks per trial were possible. A total of 11 attacks was observed: two complete attacks, and nine incomplete attacks. Attacks were considered complete if the spider inserted its chelicerae into the salamander and incomplete if the spider did not. In response to complete attacks, the salamander would flip onto its back. Salamanders occasionally responded to incomplete attacks by continuously raising and lowering their heads. To our knowledge, this behaviour is undescribed in this group of salamanders. An additional experiment investigated the influence of increased levels of salamander movement on this interaction. In this experiment, spiders preyed upon salamanders in one of eight trials and attacked salamanders in six trials (28 total attacks: four complete attacks, 24 incomplete attacks). The results of this study indicate that wolf spiders can prey upon juvenile spotted salamanders, and that the ecological relationship between wolf spiders and amphibians may be quite complex.