Antipredator behaviour of native freshwater snails (Sulcospira hainanensis) against the critically endangered big-headed turtle (Platysternon megacephalum)

Predators can trigger antipredator behaviour in their prey, leading to a cascading effect on community composition and nutrient cycling. The big-headed turtle ( Platysternon megacephalum ) frequently predates on freshwater snails ( Sulcospira hainanensis ) in Hong Kong hill streams. This study aims to detect and measure the antipredator behaviour of S. hainanensis in response to chemical (e.g., olfactory) signals from P. megacephalum and dead conspecifics. The snails were subject to four treatments: 1) no chemical signals (control), 2) chemical cues from dead conspecifics, 3) chemical cues from predators (turtle), and 4) combination of chemical cues from dead conspecifics and predators. Chemical cues from predators were the only treatment triggered a significant prey response in which they hid under a refuge. The wild population of P. megacephalum has declined because of poaching. Our findings suggest that this may lead to cascading effect on the stream ecosystem (e.g., level of primary productivity) via a weakened prey response in snails.