Almbro Maria, Kullberg Cecilia
Department of Zoology, Stockholm University, SE-106 91, Stockholm, Sweden.
J Exp Biol. 2008 Jan;211(Pt 1):24-8. doi: 10.1242/jeb.008219.
For an animal to escape an attacking predator, speed and manoeuvrability are likely to be crucial factors. Previous studies on reptiles and birds have revealed that gaining weight, due to for instance egg load or lipid accumulation, leads to impaired escape ability and possibly increases the risk of being caught by predators. Here we tested whether the flight performance of an insect, the small tortoiseshell butterfly (Aglais urticae), is affected by variations in body mass due to feeding by comparing flight performance parameters between individuals that (i) took flight spontaneously or after being subjected to a simulated predator attack and (ii) varied in flight muscle ratio (FMR: thorax mass/total body mass). The results show that butterflies that were subjected to a simulated predator attack flew at higher velocities and straighter than butterflies that were allowed to take off spontaneously. Furthermore, our study suggests, for the first time, that butterflies may experience impaired escape ability after feeding, which directly leads to a decrease in FMR; a reduction from 0.5 to 0.3 reduced escape flight velocity by about 37% at 0.5 m from the start. Finally, this study shows that FMR affects take-off angle and sinuosity, with steeper angles and more turning in butterflies with low FMR.
对于动物来说，要逃离攻击它的捕食者，速度和机动性可能是关键因素。先前对爬行动物和鸟类的研究表明，例如由于卵负荷或脂质积累导致体重增加，会导致逃逸能力受损，并可能增加被捕食者捕获的风险。在这里，我们通过比较以下个体之间的飞行性能参数来测试昆虫——小龟纹蝶（Aglais urticae）的飞行性能是否会受到因进食导致的体重变化的影响：（i）自发起飞或在遭受模拟捕食者攻击后起飞的个体，以及（ii）飞行肌肉比率（FMR：胸部质量/总体重）不同的个体。结果表明，遭受模拟捕食者攻击的蝴蝶比自发起飞的蝴蝶飞得更快、更直。此外，我们的研究首次表明，蝴蝶在进食后可能会出现逃逸能力受损的情况，这直接导致FMR降低；从0.5降至0.3会使距起点0.5米处的逃逸飞行速度降低约37%。最后，这项研究表明FMR会影响起飞角度和弯曲度，FMR较低的蝴蝶起飞角度更陡，转弯更多。
