Acoustic monitoring reveals year-round calling by invasive toads in tropical Australia

Abstract

Long-term recordings of acoustic signals allow us to reveal biological patterns not previously available. We aimed to determine the patterns of chorusing of the invasive cane toad, Rhinella marina, in a tropical savanna region in Australia where they are common and investigate the influence of environmental variables. We collected continuous acoustic recordings over 19 months at multiple sites and used call recognition software and graphical visualisation of sound files to detect toad calling. Our results revealed that cane toads are continuous breeders with chorus activity highest in the wet season but frequently occurring throughout the dry season. Daily temperatures influenced chorus activity – negatively in the wet season and positively in the dry season. Daily rainfall was positively associated with chorusing in the wet season but was not a factor in the dry season. Nightly cane toad chorus occurrence was autocorrelated on successive nights, and patterns varied among study sites under the influence of similar weather conditions, indicating factors other than weather are important in driving chorus activity of cane toads. We show that, with semi-automated analysis tools, continuous recording allows sampling to be extended over greater temporal and spatial scales, revealing patterns in the behaviour of an invasive anuran.