A comparison of humpback whale singing and ambient noise cycles in the Gulf of Tribugá, Chocó, Colombia

Abstract

To monitor potential changes in the humpback whale (Megaptera novaeangliae) singing cycle, typical singing intensities, and acoustic behaviors requires a baseline understanding of singing activity in the context of an acoustic environment that is minimally disturbed. The Gulf of Tribugá in the Colombian Pacific (the breeding ground for Stock G) was named a Hope Spot in June 2019 as a local conservation campaign against the Colombian government’s plans to build an international port here. To document this minimally disturbed acoustic ecosystem, data were recorded at Morro Mico from October to November 2018. An Ecological Acoustic Recorder (EAR) collected data on a 33.3% duty cycle at a 15 kHz sampling rate. Power spectral densities were explored across several bands up to 6250 Hz and were used to rank sound source influence and to detect diel and lunar cycles. Spectrograms in Raven Pro 1.5 were used to manually classify sounds into six groups: dolphins, humpback whales, fish, wind and rain, snapping shrimp, and boats. These sound source time series combined with power spectral density and humpback whale song intensity cycles now serves as the first year of a baseline study in preparation to document the effects of a pending major construction project.