Influence of gaze and directness of approach on the escape responses of the Indian rock lizard, Psammophilus dorsalis (Gray, 1831)

Animals often evaluate the degree of risk posed by a predator and respond accordingly. Since many predators orient their eyes towards prey while attacking, predator gaze and directness of approach could serve as conspicuous indicators of risk to prey. The ability to perceive these cues and discriminate between high and low predation risk should benefit prey species through both higher survival and decreased energy expenditure. We experimentally examined whether Indian rock lizards (Psammophilus dorsalis) can perceive these two indicators of predation risk by measuring the variation in their fleeing behaviour in response to type of gaze and approach by a human predator. Overall, we found that the gaze and approach of the predator influenced flight initiation distance, which also varied with attributes of the prey (i.e. size/sex and tail-raise behaviour). Flight initiation distance (FID) was 43% longer during direct approaches with direct gaze compared with tangential approaches with averted gaze. In further, exploratory, analyses, we found that FID was 23% shorter for adult male lizards than for female or young male (FYM) lizards. In addition, FYM lizards that showed a tail-raise display during approach had a 71% longer FID than those that did not. Our results suggest that multiple factors influence the decision to flee in animals. Further studies are needed to test the generality of these factors and to investigate the proximate mechanisms underlying flight decisions.

动物通常会评估捕食者所带来的风险程度，并做出相应的应对行为。由于多数捕食者在攻击时会将视线朝向猎物，因此捕食者的注视行为与接近的直接程度，可作为向猎物传递风险的显著线索。能够感知这些线索并区分高低捕食风险的能力，可通过提升猎物的存活率与降低能量消耗，使猎物物种获益。

我们通过测量印度岩蜥（Psammophilus dorsalis）对人类模拟捕食者的注视类型与接近方式所产生的逃逸行为变化，实验检验了其是否能够感知这两类捕食风险线索。整体而言，我们发现捕食者的注视行为与接近方式会影响逃逸起始距离（flight initiation distance, FID），而该距离也会随猎物自身属性（如体型/性别以及摆尾行为）发生变化。当捕食者采用直面注视且正面接近时，其逃逸起始距离（FID）较视线偏移的切线接近场景延长了43%。

在后续的探索性分析中，我们发现成年雄性蜥蜴的FID较雌性或青年雄性（FYM）蜥蜴短23%。此外，在接近过程中出现摆尾展示行为的青年雄性（FYM）蜥蜴，其FID较未出现该行为的个体高出71%。

本研究结果表明，多种因素会共同影响动物的逃逸决策。未来仍需开展进一步研究，以验证这些影响因素的普适性，并探究逃逸决策背后的近端机制。