Vocal communication is critical to a wide range of vertebrates, and its disruption may reduce fitness. Anuran males call to attract females, and the calls of invasive species may interfere with communication by reducing signaling efficacy. To investigate the effects of soundscape invasion on native species, we played invasive Cane Toad (Rhinella marina) calls and control synthetic pure tones to Fat Toadlets (Uperoleia crassa) on Groote Eylandt, Australia. We aimed to examine the following effects on Fat Toadlet vocal behavior: 1) do Cane Toad calls and synthetic noise elicit a similar response, 2) do high-level noises elicit a stronger response than low-level noises, and 3) what is the influence of noise frequencies outside those of their own calls? Toadlets increased call effort in response to most noise treatments. Toadlets significantly lowered dominant frequency in response to the high-level pure tones, indicating that noise amplitude had a strong influence on call spectral properties. Toadlets adjusted calls similarly in response to Cane Toad calls and pure tones, although Cane Toad calls elicited less of a response than some tones. These results revealed a general increase in call effort in response to noise rather than a specific response to an invasive species call. More research is needed to understand the full effects of soundscape invasion, including fitness costs associated with call adjustment.

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