Escape behavior in nine species of acridid grasshoppers

A prey animal confronted with an approaching predator must choose when to flee with care. Delaying flight increases the risk of capture, but fleeing also prevents an animal from exploiting resources on the patch it flees from. For cryptic animals flight also reveals the presence of an animal which may otherwise have been undetected. Given the differences between species in detection ability, flight ability, crypsis, and the habitat choices that effect these we should expect to see species-specific flight initiation distances and flight distances. While this expectation has been tested repeatedly on vertebrates it has not been examined to the same depth in invertebrate groups. We attempted to verify the presence of species-specific flight initiation distances and flight distances in nine species of acridid grasshoppers and then link the expected variation in escape behavior to ecological factors. The same observer served as a model predator in all approaches, which were made at the same speed while the observer looked directly at the subject grasshopper. Species was found to be a strong predictor of both flight initiation distance and flight distance. Neither approach nor flight distance were correlated to habitat choice. Both measures of escape behavior were more effectively predicted by phylogeny. This suggests that grasshoppers species entering new habitats across evolutionary timescales are phylogenetically constrained in the flexibility of their escape responses.