Silence is sexy: Soundscape complexity alters mate choice in túngara frogs

Many animals acoustically communicate in large aggregations, producing
biotic soundscapes. In turn, these natural soundscapes can influence the
efficacy of animal communication, yet little is known about how variation
in soundscape interferes with animals that communicate acoustically. We
quantified this variation by analyzing natural soundscapes with the
mid-frequency cover index and by measuring the frequency ranges and call
rates of the most common acoustically communicating species. We then
tested female mate choice in the túngara frog (Physalaemus pustulosus) in
varying types of background chorus noise. We broadcast two natural túngara
frog calls as a stimulus and altered the densities (duty cycles) of
natural calls from conspecifics and heterospecifics to form the different
types of chorus noise. During both conspecific and heterospecific chorus
noise treatments, females demonstrated similar preferences for
advertisement calls at low and mid noise densities but failed to express a
preference in the presence of high noise density. Our data also suggest
that nights with high densities of chorus noise from conspecifics and
heterospecifics are common in some breeding ponds, and on nights with high
noise density, the soundscape plays an important role diminishing the
accuracy of female decision-making.