Experimental Investigation into the Visual Cues Influencing Predatory Strikes by Praying Mantises Miomantis caffra and Orthodera novaezealandiae (Mantodea)

Abstract

Within nature, an ongoing evolutionary battle for survival occurs between predators and their prey. As such, the degree of detectability of prey to their predators can vary according to many visual cues. Prey speed, movement style, size, contrast, colouration and degree of background matching can interact to influence the likelihood of detection and attack by predators. In this study, I used animated models to investigate the detectability of virtual prey exhibiting variation in these traits to females of the two species of praying mantids present in Aotearoa New Zealand; the native Orthodera novaezealandiae and introduced Miomantis caffra. These experiments determined variation in response rates for many of the traits tested. I found the greatest response from both mantis species to be towards small, slow, black models travelling in a tortuous movement style, yet variation occurred in strike likelihood and the latency to strike for different speeds and sizes of prey. Subsequent experiments with M. caffra found higher response rates occurred towards models moving against a white background compared to a black background. Furthermore, a greater strike response latency occurred when models were presented against black backgrounds, compared to white backgrounds. Final experiments with M. caffra found models with cryptic traits of disruptive patterns and background matching did not result in reduced levels of detection and attack. In fact, disruptive patterns had a comparatively faster response time, alongside a low response rate towards conspicuous white models of high contrast. I propose these trends may relate to avoidance of aposematic patterns in reducing response towards bright white models, potentially due to learned or innate mantis behaviours. The inefficacy of complex cryptic appearances in reducing detectability to mantids serves to exemplify the effects of motion in ‘breaking’ camouflage. Overall, mantids prove to be a viable tool to investigate highly sensitive and complex vision systems, with application to better understanding interactions between predators and prey.