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禀赋，权衡信号强度（signal intensity）与能量消耗（energy expenditure）；信号结构（signal structure）的变异或与食物可获得性（food availability）存在关联。然而，现有多数研究证据均聚焦于鸟类与蛙类的发声信号（vocal signals），而食物可获得性对视觉运动信号（visual motion signal）的影响迄今仍未明确。本研究以亚洲鬣蜥科蜥蜴（Asian agamid lizard）青海沙蜥（Phrynocephalus vlangalii）为研究对象，探讨了尾部展示强度（tail display intensity）与食物可获得性之间的关联。实验设置了两组食物限制处理组与一组自然对照条件，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，其平均尾部展示速度（average tail display speed）与最大展示速度（maximum display speed）均出现下降，但其平均展示时长（average display duration）保持一致。综上，本研究提供了直接证据，证明蜥蜴会依据食物可获得性权衡其展示强度；该结果暗示，尾部展示速度存在代谢代价，或可作为反映个体身体状况（individual body condition）与资源持有潜力（resource hold potential）的诚实信号（honest indicator）。