The effect of distastefulness and conspicuous coloration on the post-attack rejection behaviour of predators and survival of prey

Abstract

Aposematic insects use bright colours and/or distinct markings to advertise their toxins to potential predators. When toxins are bitter-tasting and detectable upon attack, birds are able to use taste when making decisions about whether or not to eat defended prey. Taste-rejection behaviour, when birds taste but do not ingest a prey item, is often assumed to increase the survival of defended prey, yet few empirical studies have investigated the post-attack survival rates of live defended insects. We used na€ ıve domestic chicks (Gallus gallus domesticus) foraging on live waxmoth larvae (Galleria mellonella) in a laboratory setting, where conspicuousness and distastefulness could be controlled and manipulated to investigate the effects of taste-rejection behaviour, as well as the associated handling behaviour, on post-attack survival of prey. We found that being distasteful increased the probability of being rejected by na€ ıve chicks, and taste-rejection behaviour tended to be more frequent when distasteful prey were conspicuous compared with when they were cryptic. Conspicuous coloration also appeared to affect predators' assessment of prey distastefulness, with past experience strongly influencing the probability that conspicuous (but not cryptic) prey were rejected. However, in contrast to previous findings, there was no evidence that either distastefulness or conspicuousness altered how predators handled the prey before making a decision about whether or not to eat it, in any way that enhanced prey survival post-attack. Therefore, tasterejection behaviour appears to be a useful measure of prey survival. Our results provide novel insights into the potential importance of signal conspicuousness for prey populations with variable defences, and highlight the need to consider the role of taste-rejection behaviour in mimicry dynamics.

Meta-analytic evidence for quantitative honesty in aposematic signals

“…Common terrestrial [61][62][63][64] and marine [65] generalist predators are capable of taste-rejecting prey on the basis of their chemical defences, as well as discriminating among the visual features of signals [66][67][68]. Conspicuousness and defences have also been shown to interact to increase the probability of prey rejection [69,70], in part through a learned wariness toward conspicuous prey [71]. The taxonomic and ecological breadth of this work suggests 'go-slow' sampling as an appealing catch-all explanation, in keeping with the generality of our findings (table 2).…”

Multiple modalities in insect warning displays have additive effects against wild avian predators

“…taste rejected). This means that white moths are protected at the last line of defence and may rely more on taste rejection by predators (Skelhorn and Rowe 2006a, b;Halpin and Rowe 2017), which could contribute to balancing the fitness of the two morphs in the wild.…”

It’s a Matter of Taste: Avian Predators Taste Reject Mimetic Prey in Relation to Signal Reliability

“…Therefore, it is reasonable to expect that in this study, more mimics were eaten than models after they were attacked because taste sampling allows predators to discriminate between prey with ambiguous warning signals using taste. We also did not estimate prey survival, but previous studies show that taste sampled prey can often survive predator attacks [37][38][39][40] and defended prey may be attacked with less force than undefended prey [21,41,42]. Moreover, aposematic species often evolve tough and exible bodies [43][44][45] meaning that models may have higher survival than mimics [3].…”