Vocal repertoire of the freshwater dolphins Inia geoffrensis and Sotalia fluviatilis in Colombia, South America

Abstract

The Omacha Foundation conducted a project to identify and compare vocal repertoires of the freshwater dolphins Inia geoffrensis and Sotalia fluviatilis in the Amazon and Orinoco Rivers in Colombia. Field recordings of 2457 min. were made using an omnidirectional hydrophone connected to a cassette recorder. Six different types of sounds were identified for Inia geoffrensis humboldtiana in the Orinoco River. Low-frequency whistles were recorded (fundamental signal around 3 kHz, maximum frequencies of 13 kHz), when foraging/socializing dolphin groups consisted of more than five animals. Screams, squeaks, pulsed sounds, low-frequency sounds, and echolocation clicks were identified as additional sound types for the species. In the Amazon region, where both species of river dolphins are found, recordings were only analyzed when the species occurred separately. Four different types of vocalizations including echolocation clicks, screams, squeaks, and pulsed sounds were identified for Inia geoffrensis geoffrensis. No clear whistles were heard for this species. Sotalia fluviatilis whistled constantly, even when only two dolphins were sighted. Whistles varied in frequency contour and duration. Generally high frequencies were observed with maximum values of 21.7 kHz and a fundamental signal of 15.8 kHz. Squeaking sounds, echolocation clicks, and burst pulses were also recorded. (To be presented in Spanish.)