Startle response of the invasive Asian shore crab under different environmental conditions.
In recent years, researchers have recognized the importance of behavioral factors for invasive species success. There is evidence that an organism's ability to quickly react to stimuli may be one behavioral factor leading to invasive success. In this study, we analyzed the startle response of the invasive Asian shore crab Hemigrapsus sanguineus (De Haan, 1835), which measured here as a binary response variable of either active or inactive behavior when the rock they were under was suddenly lifted up. The behavior of H. sanguineus was compared to other crab species in the area to determine how species-dependent their responses were. This response was compared across an intertidal gradient with variation in temperature, intertidal elevation, substrate, time of day, and male-to-female ratios to determine if these affected the crabs' responses. We found that H. sanguineus was more responsive than other species, perhaps indicative of a generally high activity level for this species. Surprisingly, we found that their behavior was not affected by any environmental factors tested. The consistently active behavior of this crab could be one factor contributing to its high level of success as an invasive species.