Honest Signaling and Assessments of Fighting Ability

Game theory models of the evolution of animal contests predict that signaling systems should evolve to allow individuals to use the information conveyed in communication signals to assess the resource holding potential, or fighting ability, of their opponents. One goal of my research has been to examine how frogs assess the size and fighting ability of opponents using acoustic communication signals. The pitch of frog calls is widely cited as an unbluffable signal of size and fighting ability because pitch is strongly and negatively related to body size, and because larger frogs usually win aggressive physical encounters against smaller opponents. My research has demonstrated that two frogs in the family Ranidae actively lower the pitch of their calls during aggressive territorial encounters, thereby effectively imitating the calls of larger individuals (Bee & Perrill 1996; Bee & Bowling 2002). One hypothesis for pitch reductions is that frogs have evolved the ability to acoustically "bluff" their opponents during aggressive encounters. In green frogs (Rana clamitans), males differentially respond to acoustic stimuli simulating large and small males, suggesting an assessment role for call pitch (Bee et al. 1999), and the patterns of responses to simulated opponents of different sizes are consistent with predictions from some game theory models of dishonest signaling (Bee et al. 2000). In contrast to green frogs, male bullfrogs (R. catesbeiana) do not respond differentially to stimuli simulating small, large, and size-matched opponents, suggesting that pitch may have been devalued over evolutionary time as a reliable size assessment signal in this species (Bee 2002).

Related Publications:

• Bee MA and Bowling AC (2002) Socially-mediated pitch alteration by territorial male bullfrogs, Rana catesbeiana. Journal of Herpetology, 36, 140-143. PDF

• Bee MA (2002) Territorial male bullfrogs (Rana catesbeiana) do not assess fighting ability based on size-related variation in acoustic signals. Behavioral Ecology, 13, 109-124. PDF

• Bee MA, Perrill SA, and Owen PC (2000) Male green frogs lower the pitch of acoustic signals in defense of territories: a possible dishonest signal of size? Behavioral Ecology, 11, 169-177. PDF

• Bee MA, Perrill SA, and Owen PC (1999) Size assessment in simulated territorial encounters between male green frogs (Rana clamitans). Behavioral Ecology and Sociobiology, 45, 177-184. PDF

• Bee MA and Perrill SA (1996) Responses to conspecific advertisement calls in the green frog (Rana clamitans) and their role in male-male communication. Behaviour, 133, 283-301. PDF