One is the Loneliest Number but Three’s a Crowd: How Social Dynamics Influence Male Vocalizations in a Neotropical Treefrog
Ben Gregory ’20 and Professor Justin Touchon
Communication is vital to the reproductive success of many animal species—males often use signals to establish and defend territories as well as to attract mates. Males of the Neotropical treefrog Dendropsophus ebraccatus produce advertisement calls that may carry information about their fitness, typically through the dominant frequency of the call. Aside from soliciting females, the males also produce aggressive calls to compete amongst each other and will attempt to mask their competitors’ calls with their own. Previous research on this topic has been done exclusively in the field, whereas the present study investigated inter-male calling phenomena in a lab-reared colony of D. ebraccatus by first collecting and analyzing advertisement calls from the colony’s males, and then by organizing males into competitive choruses ranging from one to four males in an acoustically insulated chamber. Initial advertisement call data revealed no correlation between size and dominant frequency, but these data came overwhelmingly from males calling in isolation. In the presence of higher competition, individual males tended to increase their rate of calling and the frequency of aggressive calls, as well as the use of additional clicks at the ends of the calls, which have previously been shown to be attractive to females. Thus, this research bolsters the findings of field studies by demonstrating that male advertisement calls—presumably directed at females—are largely influenced by the competitive environment of nearby males.