Relaxed predation hinders development of anti‐predator behaviors in an aposematic beetle

Abstract

Predation is a key force constraining the time and space in which prey can forage. Theoretical models propose that warning coloration (aposematism) may help unprofitable prey to extend their foraging niche without suffering the costs of predation. In this study, we show that aposematism can alter the development of those behaviors that are associated with detection by predators. The aposematic rove beetle Paederus fuscipes Curtis (Coleoptera: Staphylinidae) harbors a symbiotic bacterium, which produces a non-proteinaceous compound named pederin. We showed that pederin is highly toxic orally to insect predators and that adult P. fuscipes are well protected against predators. Field analysis revealed that Paederus is the most abundant genus of the tribe Paederini compared to five other closely related genera and that adult Paederus beetles are much more likely to be discovered during the day in open areas. In addition, laboratory analysis of common anti-predator behaviors in P. fuscipes and three closely related, but non-toxic, rove beetles revealed that non-toxic beetles tend to seek refuge immediately after stimulation. Conversely, adult P. fuscipes are not adapted to conceal themselves even when intensely threatened. Instead, they walk in open areas and climb plant stalks, two behaviors that expose them to predators. These results imply that the chemical defense of P. fuscipes may have relaxed selective pressures on the development and maintenance of anti-predator behaviors. These findings explain the unique biological characteristics of P. fuscipes beetles and provide evidence that aposematic animals may gain benefit by extending their foraging activities across both time and space.

Out in the open: behavior’s effect on predation risk and thermoregulation by aposematic caterpillars

“…Our findings support “a classic view of aposematism” in which conspicuousness reduces the likelihood of recognition errors because predators can detect conspicuous prey at a greater distance and, thus, avoid them more reliably ( Guilford 1986 ). There has, however, been surprisingly few systematic observations of microhabitat selection by aposematic prey in this regard (but see Tabadkani and Nozari 2014 ; Rößler et al 2019 ).…”

“…This benefit of aposematism effectively negates the opposing selection faced by cryptic organisms between behaviors that maximize resource use (including favorable thermal environments) and minimize predator exposure ( Speed and Ruxton 2005 ). Multiple other aposematic animals behave in ways that expose them more to predators than comparable cryptic animals ( Pinheiro 1996 , 2007 ; Rudh et al 2013 ; Willink et al 2013 ; Tabadkani and Nozari 2014 ; Valkonen et al 2014 ; Rößler et al 2019 ). Based on our results, we predict that aposematic organisms may frequently use different microhabitats from cryptic organisms and may show reduced behavioral variation at least in terms of habitat preference or antipredator behavior.…”