Meeting Abstract

60.4  Thursday, Jan. 6  Call timing in the treefrog Dendropsophus ebraccatus: the role of the aggressive call REICHERT, M.S.; University of Missouri, Columbia msrgh9@mizzou.edu

In frog choruses acoustic competition to attract mates can be severe. One striking form of acoustic competition in many species is the precise timing of calls relative to those of other individuals. Males often overlap or avoid overlapping of other males’ calls more than expected by chance, and females show preferences for calls timed in specific positions. The treefrog Dendropsophus ebraccatus has a particularly rich repertoire of call timing arrangements: when males give advertisement (mating) calls these tend to follow, and overlap with, other males’ calls. When males respond with aggressive calls however, these do not overlap. Females prefer lagging to leading advertisement calls and advertisement calls to aggressive calls when presented in alternation. These preferences are puzzling: males calling in the leading position are at a disadvantage and thus would be better off not calling at all. This would lead to a war of attrition in which no males call. I suggest that leading males can and do overcome this disadvantage by switching to the production of aggressive calls. Aggressive calls are longer than advertisement calls, and lagging males often respond with advertisement calls to aggressive calls. Thus, a leading aggressive call often ends after a lagging advertisement call. Females appear to have preferences for the call that ends last, and I show that when a leading aggressive call is overlapped by an advertisement call, the aggressive call is no longer less attractive. This result is unusual because female frogs generally show preferences for advertisement calls over aggressive calls. In addition I will show that males in the leading position are more likely to switch to aggressive calls in natural calling interactions. These data help explain the high levels of aggressive calling observed in this species.