Data from: Competition during thermoregulation altered the body temperatures and hormone levels of lizards

Every organism must thermoregulate to maximize its performance, but competing organisms limit access to preferred microclimates. Such competition often creates hierarchies in which dominant individuals have more access to limited resources than subordinate individuals.
To assess the costs of competition during thermoregulation, we measured thermoregulation, movement, and hormones of male lizards (Sceloporus jarrovi) when alone and when paired with a smaller or larger conspecific.
Large males were 31% closer to the heat source when paired than when alone, resulting in a higher mean body temperature (35.7°C vs. 33.9°C). Conversely, small males were 40% farther from the heat source when paired, resulting in lower mean body temperature (32.1°C vs. 33.6°C).
When paired, large and small males to circulate 26% and 44% more corticosterone, respectively. Conversely, large males circulated 26% more testosterone when paired, while small males circulated 26% less testosterone.
Both dominant and subordinate males incurred costs when paired, including poorer thermoregulation, more movement, and greater physiological stress. Thus, competition for thermal resources should feature more prominently in ecological and evolutionary models of thermoregulation.

所有生物都必须通过体温调节（thermoregulation）来最大化自身机能表现，但种内竞争会限制其获取适宜微气候（microclimate）的机会。这类竞争往往会形成等级体系：优势个体相较于从属个体，能够获得更多有限资源。为评估体温调节过程中竞争所带来的代价，我们对单独饲养时，以及与体型更小或更大的同种个体（conspecific）配对饲养的雄性蜥蜴（Sceloporus jarrovi）的体温调节行为、运动情况及激素水平进行了测定。与单独饲养状态相比，体型较大的雄性蜥蜴在配对饲养时距离热源的距离近31%，平均体温随之升高（35.7℃ vs 33.9℃）。与之相反，体型较小的雄性蜥蜴在配对饲养时距离热源的距离远40%，平均体温随之降低（32.1℃ vs 33.6℃）。配对饲养时，体型较大与较小的雄性蜥蜴的循环皮质酮（corticosterone）水平分别升高26%与44%。与之相反，配对饲养的体型较大雄性的循环睾酮（testosterone）水平升高26%，而体型较小雄性的循环睾酮水平则降低26%。无论是优势雄性还是从属雄性，在配对饲养时均需付出相应代价，包括体温调节能力下降、运动增多以及更高的生理应激水平。因此，热资源竞争应当在体温调节的生态学与进化模型中占据更为突出的地位。