Failure to launch? The influence of limb autotomy on the escape behavior of a semiaquatic grasshopper Paroxya atlantica (Acrididae)

Autotomy is an extreme escape tactic where an animal sheds an appendage to escape predation. Many species alter their behavior postautotomy to compensate for this loss. We examined the escape behavior in the field of a semiaquatic grasshopper (Paroxya atlantica) that could escape either by flight and landing in vegetation or flight and landing in water and swimming to safety. We predicted that animals missing a hind limb would be more reactive (i.e., have longer flight initiation distances; FID) and would prefer to escape to vegetation rather than to water as loss of a limb is likely to reduce swimming ability. However, our predictions were not supported. FID in autotomized animals was not different from that in intact animals. Furthermore, although autotomized grasshoppers paused more often and swam slower than intact individuals, autotomized grasshoppers more often escaped to water, reaching it via shorter flights that were lateral to the approach of the observer (intact grasshoppers more often flew directly away from the observer). We also noted differences in behavior before disturbance: Autotomised animals perched lower on emergent vegetation than did intact ones, presumably in readiness for escape via water, and also showed a greater likelihood to hide (squirreling) from the approaching observer prior to launch into flight. It seems likely that the reduced flight distance and greater propensity to land in water for autotomized P. atlantica may reflect a failure to launch from their perch due to loss of a jumping back leg.