Jaguajir rochae is able to perceive differences between small and large prey and make decisions regarding venom usage

Several studies have shown that scorpions have different strategies for optimizing the venom use. The reason for this is of course because it take times to renew the venom and it is costly as the venom is a mixture of complex proteins. This is often called the venom optimization hypothesis. This also means that optimizing venom usage might directly affect the predatory behavior and physiology of scorpions.

Meykson Alexandre da Silva and co-workers have recently published an article showing that the amount of venom available for individuals of Jaguajir rochae (Borelli, 1910) (Butidae) did have an effect on their prey capture behavior. Individuals with depleted venom glands did not attack large prey, but did try to catch smaller prey that could be handled with pedipalps only. The study shows that this scorpion is able to perceive differences between small and large prey and make decisions regarding venom usage. These results are in accordance with the the venom optimization hypothesis

Abstract:
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.

Reference:
Silva MA, Silvia NA, Lira AFA, Martins RD. Role of venom quantity in the feeding behavior of Jaguajir rochae (Scorpiones: Buthidae). Acta Ethologica. 2019;Published Online 09 March 2019. [Subscription required for full text]

Thanks to Meykson Alexandre da Silva for sending me their interesting article which confirm some of the assumptions that I did in my old studies of sting use in scorpions.