Male and female responses to call playback in the Andean frog Colostethus subpunctatus

Abstract

Because Colostethus subpunctatus males tend to aggregate, it is likely that calling neighbours communicate vocally. Males advertise by producing long series of short notes at regular intervals. Note repetition rates may vary individually. To determine whether the vocal response to playback of an individual's own advertisement call depended mainly on his initial note repetition rate or on temperature, I experimented with 49 isolated calling males under field conditions. Two different responses occurred. The response type was independent of initial note repetition rate and ambient temperature. Twenty-six males maintained the basic pattern of the advertisement call, but irrespective of temperature they significantly increased note repetition rate in correlation to the initial rate. Twenty-three males changed their call pattern by grouping 2-3 notes into a bout with much shorter silent intervals between notes. Bout repetition rate was also correlated with the initial note rate, but it was lower. To interpret the role of different call patterns, phonotaxis behaviour of twelve females was studied in two-choice laboratory experiments. Each female had the opportunity to choose four times between the advertisement call with low and high note repetition rate, and four times between the latter and the bout. Females tended to choose the high repetition rate more often than the low rate or the bout. The study provides support that an increase in note repetition rate gives competitive advantage to the caller in attracting a female. Bouts are probably aggressive signals used by a resident to repel intruders from his calling site.