Impact of chemical stimuli on feeding behavior of invasive crayfish, Procambarus clarkii

Predator-prey dynamics are a central driving force in ecological communities which are altered when non-native species invade and can result in substantial biodiversity loss of native species (Ilhéu, 2007). Many ecological factors such as native species and environmental features impact how effective invasive species are in invading new habitats. Invasive crayfish, Procambarus clarkii, are currently invading freshwater streams in the Santa Monica Mountains and have been found in other studies to cause trophic cascades due to their omnivorous feeding behavior (Rodríguez, 2005). Native species are currently declining, and in some instances, locally extinct due to crayfish (Kats, 2003). We measured the feeding behavior of P. clarkii on mosquito larvae in the presence of three different native factors: a high nitrate solution (25 ppm) to mimic pollution present in many local streams, a neurotoxin solution (tetrodotoxin) that is secreted by the California newt (Taricha torosa), and an amphibian cue solution created using the California tree frog (Pseudacris cadaverina). The P. cadaverina solution acts as a control for the tetrodotoxin solution since newts produce both the neurotoxin as well as amphibian cues. The presence of these different native chemical cues (high nitrates, tetrodotoxin, and amphibian cues) resulted in significantly different P. clarkii feeding behavior of mosquito larvae. Crayfish ate significantly less mosquito larvae in the presence of the amphibian cues than in the presence of other cues. These findings indicate the significance of native amphibian preservation on feeding behavior as a proxy for the success of crayfish invasion of stream ecosystems