Data from: Ground squirrel tail-flag displays alter both predatory strike and ambush site selection behaviours of rattlesnakes

Many species approach, inspect, and signal toward their predators. These behaviours are often interpreted as predator-deterrent signals—honest signals that indicate to predators that continued hunting is likely to be futile. However, many of these putative predator-deterrent signals are given when no predator is present, and it remains unclear if and why such signals deter predators. We examined the effects of one such signal, the tail-flag display of California ground squirrels, which is frequently given both during and outside direct encounters with northern Pacific rattlesnakes. We video recorded and quantified the ambush foraging responses of rattlesnakes to tail-flagging displays from ground squirrels. We found that tail-flagging deterred snakes from striking squirrels, most likely by advertising squirrel vigilance (i.e., readiness to dodge a snake strike). We also found that tail-flagging by adult squirrels increased the likelihood that snakes would leave their ambush site, apparently by elevating the vigilance of nearby squirrels which reduces the profitability of the ambush site. Our results provide some of the first empirical evidence of the mechanisms by which a prey display, although frequently given in the absence of a predator, may still deter predators during encounters.诸多物种会对捕食者采取趋近、探查与信号传递行为。此类行为常被解读为捕食威慑信号（predator-deterrent signals）——即向捕食者传递“持续捕猎大概率徒劳无功”的诚实信号（honest signals）。然而，诸多此类假定的捕食威慑信号会在并无捕食者在场的情况下被释放，目前尚不清楚这类信号是否真能威慑捕食者，以及其威慑捕食者的具体机制。我们针对其中一类信号展开了研究：加州地松鼠（California ground squirrels）的尾摆展示（tail-flag display）行为，该行为在与北太平洋响尾蛇（northern Pacific rattlesnakes）直接遭遇期间及遭遇之外的场景中均频繁出现。我们通过录像记录并量化了响尾蛇对松鼠尾摆展示行为的伏击觅食反应。研究发现，尾摆展示能够阻止响尾蛇攻击松鼠，其潜在机制大概率是通过向响尾蛇传递松鼠的警戒状态——即具备躲避蛇类攻击的能力。此外我们还发现，成年松鼠的尾摆展示会提升响尾蛇离开伏击位点的概率，这显然是通过提高周边松鼠的警戒程度，降低了伏击位点的捕猎收益。本研究结果为这类猎物展示行为的威慑机制提供了首批实证依据之一：尽管这类行为常于无捕食者在场时发生，但仍可在遭遇捕食者的场景中实现威慑效果。