HUMFELD, Sarah C; University of Missouri-Columbia: Intrinsic and Extrinsic Factors Interact to Mediate Mating Tactic Switches

An important example of phenotypic variation is alternative behaviours used for mate acquisition. Alternative reproductive behaviours are usually considered to be a consequence of male-male competition for a limited number of females, in which only a subset of males can successfully employ the dominant mating tactic. Animals that conditionally switch between alternative mating behaviours over a short time period provide an opportunity to study the interplay of intrinsic (physiology) and extrinsic (environment) factors that mediate this decision. Male green treefrogs (Hyla cinerea) produce acoustic signals to attract females; however, some silent males adopt the satellite mating tactic, whereby they attempt to intercept females attracted to nearby calling males. Individual males can utilize both reproductive tactics within or between nights, but satellite males are on average in poorer body condition than calling males. Field observations and feeding experiments indicate that males in poor condition produce less intense and higher frequency (and therefore relatively unattractive) advertisement calls than similarly sized males in good condition. Chorusing results in competition among neighbours, so we predict that the constraints imposed by body condition on call production may play an important role in mediating mating tactic decisions. To determine whether relative detectability (intensity) and attractiveness (frequency) mediate the decision to switch mating tactics, I conducted a field playback experiment in which I observed the calling and mating tactic behaviours of males confronted with low- and high-frequency signals of varying intensity. The results indicate that competitive ability, resulting from the interplay of body condition and acoustic environment, is an important determinant of mating tactic adoption.