Tail display intensity is restricted by food availability in an Asian agamid lizard Phrynocephalus vlangalii

Individuals have to trade off their signal intensity and energy expenditure according to resource condition, and variation of signal structure likely associates with food availability. Nevertheless, most evidence come from research on vocal signals in birds and frogs, while the effect of food availability on visual motion signal is largely unknown. Here we used an Asian agamid lizard Phrynocephalus vlangalii and examined the association between tail display intensity and food availability. Two food restriction treatments as well as natural condition were designed, and tail display intensity under different food conditions was quantified. Our results shown that male lizards reduced their average tail display speed as well as maximum display speed in both food restriction treatments compared with nature reference condition, although average display duration was consistent. Therefore, our study provides direct evidence that lizards would trade off their display intensity according to food availability, which implies that tail display speed is costly and might provide honest indicator on individual body condition and resource hold potential.

个体需依据自身资源状况权衡信号强度（signal intensity）与能量消耗（energy expenditure），且信号结构的变异大概率与食物可获得性（food availability）相关。然而，现有绝大多数研究证据均来自鸟类与蛙类的发声信号研究，而食物可获得性对视觉运动信号的影响尚不明晰。本研究以亚洲鬣蜥科的青海沙蜥（Phrynocephalus vlangalii）为实验对象，探究了尾部展示强度（tail display intensity）与食物可获得性之间的关联。本研究设置了两组食物限制处理组与自然对照条件，并量化了不同食物条件下的尾部展示强度。结果显示，相较于自然对照条件，两组食物限制处理组中的雄性蜥蜴的平均尾部展示速度与最大展示速度均有所下降，但其平均展示时长保持不变。综上，本研究为蜥蜴可依据食物可获得性权衡其展示强度提供了直接证据，这表明尾部展示速度存在代谢成本，或可作为反映个体身体状况与资源储备潜力的诚实信号（honest indicator）。