Territorial songs indicate male quality in the sac-winged bat Saccopteryx bilineata (Chiroptera, Emballonuridae)

Defense of territories in many animal species involves the advertisement of territory holder quality by acoustic signaling. In the sac-winged bat Saccopteryx bilineata, males engage in territorial countersinging when reoccupying their day-roost territories in the morning and in the evening before abandoning the roost for the night. Females roost mainly in male territories, and territory holders are reproductively more successful than nonterritorial males. In territorial songs of male S. bilineata, we distinguished 6 syllable types and parameterized their acoustic properties. The analysis of 11 microsatellite loci allowed assignments of juveniles to their parents. Males had a higher reproductive success both when they uttered more territorial songs per day and when their long buzz syllables had a lower end frequency of the fundamental harmonic. Long buzzes had a harsh quality due to a pulsation of the fundamental frequency at the syllable onset and also had the highest sound pressure level of all syllable types in most territorial songs. Territorial songs and especially long buzz syllables are thus likely to advertise territory holder quality and competitive ability.