Do pit vipers assess their venom? Defensive tactics of Deinagkistrodon acutus shift with changed venom reserve.

To maximize survival probability, animals must assess predation risks and adopt flexible defensive strategies based on specific conditions. Pit vipers utilize venom for predation and self-defense, and venom status significantly influences its effectiveness. Thus, pit vipers may evaluate their venom reserve and adopt corresponding defensive tactics. Twenty-three sharp-snouted pit vipers (Deinagkistrodon acutus) were grouped by different venom status and were subjected to eight behavior trials. Subjects' defensive behaviors were recorded and analyzed. Results showed that the normal venom group displayed stable responses across the trials. The low venom group showed fewer strikes and more fleeing behaviors at the end of experiments. After given prolonged intervals for replenishing the venom, significant increases of strike behaviors were observed in the replenishing venom group. These results demonstrated the capability of adopting flexible defensive tactics based on varied venom reserve and provided new evidence for venom-status-recognition.