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 <i>Phrynocephalus vlangalii</i> 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.