Animal venom is composed of a complex mixture of protein-rich chemicals. Synthesis of animal venom incurs a high metabolic cost and is a prolonged process; consequently, animals use their venom cautiously and economically. Some studies have shown that venomous animals modulate the amount and/or type of venom used depending on certain factors, such as prey size or the intensity of predation threat. Here, we investigated how the quantity of venom that is available for use by the scorpion Jaguajir rochae interferes with its choice of prey. We used two types of prey of contrasting size (small 200–300-mg and large 600–700-mg cockroaches). The results showed that the amount of venom influences the feeding behavior of this species. Most scorpions without venom exhibited a low interest when large prey was present, but frequently attacked small prey. The scorpions also showed a distinct pattern in the time between venom extraction and the initiation of hunting behavior. In conclusion, J. rochae is able to perceive differences between small and large prey and make decisions regarding venom usage, supporting the “venom optimization hypothesis” (or “venom metering hypothesis”), by minimizing the venom use due to it being an energetically expensive resource.

中文翻译：

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毒液数量在Jaguajir rochae（蝎：Buthidae）的摄食行为中的作用

动物毒液由富含蛋白质的化学物质的复杂混合物组成。动物毒液的合成导致高新陈代谢成本，并且是一个漫长的过程。因此，动物谨慎而经济地使用其毒液。一些研究表明，有毒动物会根据某些因素（例如猎物的大小或捕食威胁的强度）来调节毒液的使用量和/或类型。在这里，我们调查了蝎子Jaguajir rochae可以利用的毒液数量干扰其猎物的选择。我们使用了两种不同大小的猎物（小200-300毫克和大600-700毫克的蟑螂）。结果表明，毒液的数量会影响该物种的摄食行为。当存在大型猎物时，大多数没有毒液的蝎子表现出较低的兴趣，但经常攻击小型猎物。在毒液提取和开始狩猎行为之间的时间里，蝎子还表现出明显的模式。总之，J。rochae能够感知到小猎物与大猎物之间的差异，并就使用毒液做出决策，支持“毒液优化假说”（或“毒液计量假说”），因为它是一种精力充沛的活动，因此最大限度地减少了毒液的使用昂贵的资源。