Rapid beard darkening predicts contest outcome, not copulation success, in bearded dragon lizards

Rapid colour change is widespread in animals and allows them to respond
dynamically to the physical and social environment. However, few studies
have examined the information conveyed by dynamic colour signals in
different social contexts, such as courtship and rivalry contests.
Furthermore, dynamic colour change on different body regions may be
subject to different selection pressures and therefore serve different
functions. We tested whether male colour or colour change
predict contest outcome in male-male interactions, or the
likelihood of copulation attempts in male-female interactions in the
central bearded dragon, Pogona vitticeps. The extent of beard
darkening strongly predicted contest outcome, but neither colour (beard,
dorsal) nor colour change predicted copulation attempts. Dorsal
colour showed little consistent change and did not predict contest outcome
or copulation attempts. Previous work shows that dorsal but not
beard colour change occurs in response to both background colour and
temperature in the laboratory and in the wild. Taken together,
these results indicate that dynamic colour change in bearded dragons
varies in relation to social context and can serve different functions
depending on the body region. Our data add to the growing
appreciation of how rapid colour change enables animals to accommodate the
multiple functions of colour, including communication to different
receivers, camouflage and thermoregulation.

动物界广泛存在快速体色变化现象，此类变化可使动物动态响应物理与社会环境。然而，目前鲜有研究关注动态体色信号在求偶、竞争对峙等不同社会场景中所传递的信息。此外，不同身体区域的动态体色变化可能承受不同的选择压力，因而具备各异的功能。我们以中部鬃狮蜥（Pogona vitticeps）为研究对象，检验雄性体色或体色变化能否预测雄性间互动的竞争结果，或是雌雄互动中雄性发起交配尝试的概率。研究结果显示，喉垂黑化程度可显著预测竞争结果，但体色（喉垂、背部）及体色变化均无法预测交配尝试行为。背部体色几乎无一致性变化，既无法预测竞争结果，亦无法预测交配尝试行为。既往研究表明，无论在实验室还是野外环境中，背部而非喉垂的体色变化会响应背景色与温度的变化。综合上述结果可知，鬃狮蜥的动态体色变化因社会场景而异，且不同身体区域的体色变化功能各不相同。本研究进一步丰富了学界关于快速体色变化如何帮助动物兼顾体色多重功能的认知，这些功能包括向不同接收者传递通讯信号、伪装以及体温调节。