Aposematic Signal Variation Predicts Male-Male Interactions in a Polymorphic Poison Frog

Abstract

Many species use conspicuous "aposematic" signals to communicate unpalatability/unprofitability to potential predators. Although aposematic traits are generally considered to be classic examples of evolution by natural selection, they can also function in the context of sexual selection, and therefore comprise exceptional systems for understanding how conspicuous signals evolve under multifarious selection. We used males from a highly territorial poison frog species in a dichotomous choice behavioral test to conduct the first examination of how aposematic signal variation influences male-male interactions. Our results reveal two behavioral patterns: (1) male dorsal brightness influences the behaviors of male conspecifics such that males approach and call to brighter males more frequently and (2) a male's dorsal brightness predicts his own behavior such that bright males approach stimulus frogs faster, direct more calls to bright stimulus frogs, and exhibit lower advertising call pulse rates (a fitness-related trait). These findings indicate the potential for sexual selection by male-male competition to impact aposematic signal evolution.

Poison Frog Colors Are Honest Signals of Toxicity, Particularly for Bird Predators

“…During conspecific social interactions, male D. pumilio adopt an upright position that exposes their ventral body areas. Ventral coloration tends to be brighter than dorsal coloration in all our study populations (M. E. Maan and M. E. Cummings, unpublished data), and coloration brightness affects both male aggression (Crothers et al 2011) and female choice (Maan and Cummings 2009). While the behavioral experiments conducted to date did not reveal sexual selection on ventral coloration, dedicated experiments that specifically address ventral coloration have yet to be conducted.…”

“…Based on these results, subsequent researchers have assumed that toxicity and coloration are independent in this species. This view has been strengthened by accumulating evidence for the role of D. pumilio coloration in intraspecific communication (Summers et al 1999;Reynolds and Fitzpatrick 2007;Cummings 2008, 2009;Crothers et al 2011;Richards-Zawacki and Cummings 2011). Here, we reevaluate this conclusion.…”

Responses to song playback vary with the vocal performance of both signal senders and receivers

“…Available evidence from several songbird species indicates that vocal performance can correlate with age, size or other quality attributes [32,33], and males with high-performance songs would therefore be better positioned to ward off the challenge of high-performance intruders. In agonistic contests, the importance of subjects' own attributes as predictors of behaviour has been established in other taxa [34], but fewer studies have shown the connection to receiver signal values specifically [7,35]. For example, in a study of hermit crabs (Pagurus berhardus), model intruders that signalled aggressively were seen to elicit varied responses, with the likelihood of different responses (attack or retreat) depending on whether study subjects had initially signalled with threat displays themselves [36].…”

Trade-off between warning signal efficacy and mating success in the wood tiger moth

“…Females prefer males based on familiar dorsal coloration, but female tolerance for unfamiliar colour patterns may facilitate the establishment of novel phenotypes that could be favoured further by predator bias [17]. Thus, the combined effects of sexual selection and predation may facilitate colour polymorphism [16][17][18].…”

“…In the strawberry poison frog (Oophaga pumilio), the aposematic coloration influences the behaviour of male conspecifics [16] and female preference [17]. Females prefer males based on familiar dorsal coloration, but female tolerance for unfamiliar colour patterns may facilitate the establishment of novel phenotypes that could be favoured further by predator bias [17].…”