Age and Appearance Shape Behavioral Responses of Phasmids in a Dynamic Environment

Abstract

Although morphological adaptations leading to crypsis or mimicry have been studied extensively, their interaction with particular behaviors to avoid detection or recognition is understudied. Yet animal behaviors interact with morphology to reduce detection risk, and the level of protection conferred likely changes according to the surrounding environment. Apart from providing a locational cue for predators, prey motion can also serve as concealing behavior in a dynamic environment to prevent detection by potential predators or prey. Phasmids are conventionally known to rely on their adaptive resemblance to plant parts for protection, and this resemblance may vary across life stages and species. However, little is known about how their behaviors interact with their appearance and their environment. We investigated two species of phasmids with varying morphology and color patterns at different ontogenetic stages and examined their behavioral responses to a wind stimulus as a proxy for a dynamic environment. While adult behaviors were mostly species-specific, behavioral responses of nymphs varied with appearance and environmental condition. Display of different behaviors classified as revealing was positively correlated, while the display of concealing behaviors, except for swaying, was mostly negatively correlated with other behaviors. Exhibition of specific behaviors varied with appearance and environmental condition, suggesting that these behavioral responses could help reduce detection or recognition cues. We discuss the differences in behavioral responses in the context of how the behaviors could reveal or conceal the phasmids from potential predators. Our results provide a novel investigation into adaptive resemblance strategies of phasmids through the interaction of behavior and morphology, and highlight the importance of considering the effects of dynamic environments on sending and receiving cues.

Interpreting animal behaviors – A cautionary note about swaying in phasmids

“…Swaying behavior was not ubiquitous across these four species: swaying was common in Lonchodes brevipes (Diapheromeridae), occasionally observed in Calvisia flavopennis (Lonchodidae) and Marmessoidea rosea (Lonchodidae), and rarely observed in Haaniella echinata (Heteropterygidae). Indeed, our study (Pohl et al, 2022) indicate that even for the same species (L. brevipes), individuals at different life stages appear to sway to different extents. More nuanced studies in the future are crucial to understand the factors affecting swaying behavior, but the appropriate biological context to consider stabilizing mechanisms in such systems is of a hanging organism.…”

“…In mantids, swaying can reduce detection by predators, cannibalistic conspecifics and prey (Watanabe and Yano, 2009, 2012, 2013. Several species of phasmids are reported to sway (Rupprecht, 1971;Bian et al, 2016;Pohl et al, 2022), with recent research on phasmids consistent with the view that phasmids adopt swaying to reduce detection (Bian et al, 2016;Pohl et al, 2022). Thus, swaying provides phasmids with a form of concealment between revealing behaviors through motion masquerade, which is the matching of an animal's motion to environmental motion, such that the animal resembles an inanimate object and prevents detection by an observer (Fleishman, 1985).…”

Imperfect ant mimicry contributes to local adaptation in a jumping spider

“…To investigate how body coloration may contribute to spider fitness, future work should make use of an experimental apparatus with a corresponding background because the environment may influence both how the spiders behave and how the predator perceives and responds to the prey. 35 , 36 Moreover, we hypothesized that the sexual dimorphism and female-limited polymorphism in S. collingwoodi may be driven by sexual selection, as documented in many jumping spiders, 37 which warrants further investigation in the future. If this hypothesis is confirmed, S. collingwoodi may serve as a remarkable example to support body color as a key visual signal in the sexual selection of jumping spiders and to illustrate the nature of such imperfect mimics that is driven by both natural and sexual selection.…”

Antipredator defences in motion: animals reduce predation risks by concealing or misleading motion signals

“…As animals will need to evaluate trade-offs on the risks of detection versus opportunity costs of mate or food location, this may not be an all-or-nothing scenario. For instance, Pohl et al (2022) suggest that stick insects may adopt swaying to provide concealment in intervals, between riskier revealing behaviours such as exploration. Such behavioural changes indicate the need for specialised adaptations to detect and adjust to surrounding changes.…”

“…For instance, Pohl et al . (2022) suggest that stick insects may adopt swaying to provide concealment in intervals, between riskier revealing behaviours such as exploration. Such behavioural changes indicate the need for specialised adaptations to detect and adjust to surrounding changes.…”