Field observations of the alarm response to crushed conspecifics in the freshwater snail Pomacea canaliculata: effects of habitat, vegetation, and body size

The freshwater snail Pomacea canaliculata shows alarm responses to chemical cues released from injured conspecifics, but its behavioural responses in the field are unknown. We investigated effects of habitat (canals or paddy fields), vegetation, and body size on alarm responses in the field. Snails responded to crushed conspecifics within 4 min by burying themselves, but the proportions of self-buried snails were generally lower (0-28% depending on experiments) than those reported in the laboratory. Snails not only showed the alarm response, but also frequently fed on crushed conspecifics. There were no influences of habitat or body size on the proportions of individuals showing the alarm response. Nevertheless, in paddy fields with high-density vegetation a higher proportion of snails showed the alarm response than in paddy fields with low-density vegetation.