Distance-dependent defensive coloration in the poison frog Dendrobates tinctorius , Dendrobatidae

Abstract

Poison dart frogs provide classic examples of warning signals: potent toxins signaled by distinctive, conspicuous coloration. We show that, counterintuitively, the bright yellow and blue-black color of (Dendrobatidae) also provides camouflage. Through computational modeling of predator vision, and a screen-based detection experiment presenting frogs at different spatial resolutions, we demonstrate that at close range the frog is highly detectable, but from a distance the colors blend together, forming effective camouflage. This result was corroborated with an in situ experiment, which found survival to be background-dependent, a feature more associated with camouflage than aposematism. Our results suggest that in the distribution of pattern elements, and the particular colors expressed, act as a highly salient close range aposematic signal, while simultaneously minimizing detectability to distant observers.

Phenotypic and genetic diversity in aposematic Malagasy poison frogs (genus Mantella)

“…In fact, studies within this system have even suggested that natural and sexual selection may operate on different aspects of frog coloration, as variation in male brightness, an important component of assortative mating and male–male interactions, is not visible to avian predators (Crothers & Cummings, ). Additionally, there is growing evidence that pattern traits in poison frogs may also be under selection (Barnett, Michalis, Scott‐Samuel, & Cuthill, ; Rojas & Endler, ; Wollenberg, Lötters, Mora‐Ferrer, & Veith, ). Studies of intrapopulation pattern variation in the poison frog Dendrobates tinctorius have demonstrated that certain pattern traits are correlated with movement behavior, suggesting that patterning elements may also be important in determining how aposematic organisms are perceived by predators (Rojas, Devillechabrolle, & Endler, ).…”

“…Studies of intrapopulation pattern variation in the poison frog Dendrobates tinctorius have demonstrated that certain pattern traits are correlated with movement behavior, suggesting that patterning elements may also be important in determining how aposematic organisms are perceived by predators (Rojas, Devillechabrolle, & Endler, ). In fact, recent work in D. tinctorius indicates that pattern and color function as an aposematic signal to predators at close range, but are perceived as cryptic when viewed from longer distances (Barnett et al, ). Future work on phenotypic diversity in Malagasy poison frogs should draw on this body of literature and consider the relative roles of natural and sexual selection in shaping phenotypes, as well as the relative contributions of color and pattern to predator avoidance.…”

“…Although we observed high degrees of pattern variation on the side and ventral surfaces of frogs in our study (Figures and ), the role of this variation is unknown. Recent work in poison frogs linking patterning elements to movement behavior and detectability by predators (Barnett et al, ; Rojas, Devillechabrolle et al, ) indicates that pattern variation may be equally, or even more, biologically relevant than color variation. Further, evidence that the detectability of different color pattern variants is influenced by the existing light environment (Rojas, Rautiala, & Mappes, ) underscores the importance of incorporating information on both predator sensory abilities and ambient lighting conditions into the characterization of phenotypic variation.…”

Camouflage

“…Furthermore, that match need only be accurate at the spatial frequency the viewer is sampling at; in other words, as limited by their visual acuity (Caves, Brandley & Johnsen, ). This allows the same pattern to function as camouflage at a distance, but a signal when the intended viewer is close (Endler, , ; Merilaita & Tullberg, ; Bohlin, Tullberg & Merilaita, ; Barnett & Cuthill, ; Barnett, Scott‐Samuel & Cuthill, ; Barnett et al ., ,b, ,b; Barnett, Cuthill & Scott‐Samuel, , ).…”

“…If the background has an oriented texture, such as the vertical grain of bark on trees such as oak, then a background‐matching animal has to orient such that its texture matches (Sargent, ; Kang et al ., , ; Barnett et al ., ,b, ,b). This demands the ability to detect the background texture, not necessarily visually because tactile cues may suffice, and orient appropriately.…”