A project undertaken at Western Sydney University, and supervised by Kate Umbers & Johanna Mappes
Arms races between prey and predators are a central theme in evolutionary biology, yet some of the most striking of prey defences have been consistently overlooked. Classic studies on prey defences focus on conspicuous colours, cryptic patterns, noxious chemicals and warning calls. Focus has rarely fallen on the dynamic in which, when under attack, prey attempt to frighten their predators by suddenly unleashing an unanticipated secondary defence e.g. a brightly coloured body part and/or exuding a noxious chemical. Known as deimatic displays (sensu Maldonado 1970), these are multicomponent, often multimodal defences.
Figure 1. An adult female mountain katydid (Acripeza reticulata) performing her deimatic display.
Empirical data on deimatic displays are scarce but the comparative lack of research attention they have received is not proportional to their abundance in nature. Observational evidence suggests that deimatic displays are common and found across phyla but progress is stagnated by the lack of a conceptual framework with which to direct hypothesis testing. Our project will develop a conceptual framework and a new empirical system for studying deimatic displays to push the boundaries of current understanding in predator prey interactions into an almost entirely unexplored, yet very interesting area.
We will employ an interdisciplinary approach that includes chemical toxicology, biophysics, movement and colour analysis. Our target species is the mountain katydid Acripeza reticulata, an Australian alpine orthopteran that performs a remarkable deimatic display that involves revealing a brightly coloured abdomen, exuding toxin and making itself appear larger (see Figures 1 & 2).
We employed an interdisciplinary approach that included behaviour, chemical toxicology, movement and colour analysis. Our target species was the mountain katydid Acripeza reticulata, an Australian alpine orthopteran that performs a remarkable deimatic display that involves revealing a brightly coloured abdomen, exuding toxin and making itself appear larger (see Figures 1 & 2).
We conducted a series of experiments on the katydid’s display that showed they are far more likely to display to tactile stimuli than visual stimuli (Umbers and Mappes 2015), the data from which were also used to demonstrate a statistical technique new to behavioural ecology (López-Sepulcre et al 2015). We tested whether katydids choose between escaping or displaying and found that they seem not to be beholden to a fight-or-flight trade off (De Bona et al in press).
In an interesting aside we noticed two Australian magpies dunking mountain katydids in puddles of water before consuming them perhaps to remove their bitter tasting exudate (Drinkwater et al 2017). We have five manuscripts yet to be published covering the mountain katydid’s chemical defence, details on predator handling behaviour of deimatic prey, wild predatory rates of attack on mountain katydid models, katydid repeatability in display behaviour, and the primary defense tactics of mountain katydids.
Figure 2. Close up on the abdomen of a female mountain katydid (Acripeza reticulata) showing colour patches and distasteful exudate.
We employed an interdisciplinary approach that included behaviour, chemical toxicology, movement and colour analysis. Our target species was the mountain katydid Acripeza reticulata, an Australian alpine orthopteran that performs a remarkable deimatic display that involves revealing a brightly coloured abdomen, exuding toxin and making itself appear larger (see Figures 1 & 2). We conducted a series of experiments on the katydid’s display that showed they are far more likely to display to tactile stimuli than visual stimuli (Umbers and Mappes 2015), the data from which were also used to demonstrate a statistical technique new to behavioural ecology (López-Sepulcre et al 2015). We tested whether katydids choose between escaping or displaying and found that they seem not to be beholden to a fight-or-flight trade off (De Bona et al in press). In an interesting aside we noticed two Australian magpies dunking mountain katydids in puddles of water before consuming them perhaps to remove their bitter tasting exudate (Drinkwater et al 2017). We have five manuscripts yet to be published covering the mountain katydid’s chemical defence, details on predator handling behaviour of deimatic prey, wild predatory rates of attack on mountain katydid models, katydid repeatability in display behaviour, and the primary defense tactics of mountain katydids.
During our exploratory analyses, we discovered that the type of display the katydids use is not easy to define and this opened up a discussion among experts in anti-predator strategies and led to several new collaborations aimed towards outlining new conceptual breaks (Umbers et al 2016, Umbers et al 2017). The discussion lead to the hypothesis that deimatic displays don’t require learning the way aposematic signals do. We tested that hypothesis and found support for the idea that naïve predators are more likely to be deterred by mountain katydid displays than predators with katydid experience (Umbers et al 2019). More work building mountain katydids as a model system in deimatic defensive displays is underway.