Strategic Deployment of Secondary Defences in the Springbok Mantis (Miomantis Caffra)

Abstract

Deimatic displays are visually conspicuous behaviours designed to prevent predation by scaring off predators. Animals that exhibit deimatic behaviours often show other secondary defences as well, but the factors that influence which defences are expressed are poorly understood. Because prey are expected to deploy multiple defences strategically, conspicuous deimatic displays could be performed later in the predation sequence after primary or other secondary defences have failed. Their expression could additionally depend on the state of the performer, especially if deimatic behaviours are costly to produce or involved in a functional trade-off. Here, we investigate female defensive responses to escalating attacks involving non-tactile and tactile stimuli by a human model predator using the springbok mantis, Miomantis caffra. We found that all defensive behaviours were expressed only after mantises were physically provoked, indicating a counter defence rather than a pre-emptive one. Most females responded to initial tactile contact with non-deimatic behaviours—most commonly fleeing, but also striking with raptorial forelegs and freezing. When predator attacks escalated and tactile contact increased, females mostly produced deimatic behaviours, including raising forelegs, flaring wings, exposing jaws and/or swaying from side to side. Females that were heavier for their size and therefore closer to oviposition were also less likely to flee and more likely to strike and display, although this pattern depended on the level of predator threat. Our results suggest that the expression of deimatic displays is prompted by the repeated failure of non-deimatic defences to ward off escalating predator attacks, which may be why deimatism has gone unnoticed in M. caffra until now. Our findings also suggest an important role for fight-or-flight trade-offs in the expression of antipredator behaviours in this species: heavier egg-loads appear to compromise females' ability to flee, triggering more aggressive and deimatic responses instead.