The franciscana dolphin is a small, vulnerable species often caught in artisanal gillnets. This study aims to provide a comprehensive assessment of their acoustic capabilities by using advanced equipment to collect a large dataset of wideband, continuous recordings. We examined the detailed acoustic signals of franciscana dolphins, comparing the sounds from rehabilitated dolphins in captivity with those of wild dolphins near fishing nets. Significant differences in acoustic characteristics were found between neonates and older dolphins, with juvenile and wild dolphins showing similar features. For the first time, repetition patterns in click production were identified, highlighting the importance of understanding the context of these sounds in regards to feeding and communication. This study emphasizes the need for detecting neonates for species protection and suggests the potential for developing acoustic classifiers specific to different age groups. Our findings offer valuable insights for conservation efforts and the development of protection strategies for franciscana dolphins.

In recent years, passive acoustics has emerged as an effective tool for detecting cetaceans, particularly in difficult-to-observe species. In addition to being a non-invasive technique, it allows for animal monitoring without disturbing them, regardless of visibility conditions. However, the high cost of the equipment associated with this technique presents a significant challenge for developing countries. The objective of this project was to compare acoustic signals of the bottlenose dolphin (Tursiops truncatus truncatus) recorded using a commercial self-contained hydrophone and a low-cost, handcrafted alternative. Recordings were conducted at the Aquarium Mar del Plata, Argentina, using both hydrophones simultaneously over a 50-min period. Recorded signals were characterized and tonal signals (whistles) detected by each device were counted. Robust parameters for each whistle were obtained using the Raven Pro software. Based on the analysis of coincident whistles, it was determined that the measured parameters did not show significant differences between the two instruments, demonstrating the effectiveness of low-cost hydrophones for acoustically monitoring bottlenose dolphins in controlled environments, with the potential for use in other settings such as open water.

This study provides the first characterization of the acoustic signals emitted by Lahille’s bottlenose dolphins (Tursiops gephyreus) in Argentine waters, establishing a baseline for the species’ southern distribution limit. Passive acoustic monitoring was conducted in the inner channels of the Bahía Blanca Estuary using a broadband hydrophone and F-POD detectors. We documented a diverse acoustic repertoire consisting of echolocation clicks, whistles, bray-calls, and chirps. Acoustic presence was predominantly diurnal and showed a marked synchronization with the tidal cycle, with peak activity occurring during the ebbing tide. Whistles had a mean center frequency of 8.1 kHz, showing spectral overlap with other regional populations in the Southwestern Atlantic. Echolocation clicks were broadband, with peak frequencies ranging from 18 to 127 kHz and a mode around 40 kHz. These results suggest that dolphin movement in the estuary’s internal channels is structured by hydrodynamics, likely reflecting foraging opportunities associated with tidal flow. Given the endangered status of this species, these data establish a technical framework for non-invasive monitoring and habitat-use assessments in complex estuarine environments.

Acoustic recording can be a very interesting way of monitoring cetaceans for conservation purposes. However, some sympatric species produce very similar sounds and are thus difficult to study specifically. In this work, we are interested in characterizing the narrow band high frequency (NBHF) clicks emitted by several species of odontocetes, among which all porpoises and some species of dolphins. The traditional acoustic parameters (durations, frequencies, bandwidths) of NBHF clicks show several drawbacks, such as redundancy, lack of precise definition, and poor robustness to noise. In this study, we propose a new method of characterizing NBHF clicks by fitting a Gabor wavelet to the signal and thus extracting two specific metrics, the Gabor frequency and the Gabor duration. We first assess the theoretical usefulness of this mathematical model, and then test it against traditional measurements in numerical examples with varying levels of noise. Our method is then applied to two empirical datasets recorded in South America, a place were many sympatric species are found to emit NBHF clicks. Two large sets of signals are thus analyzed and compared : one of clicks of Peale’s dolphins (Cephalorhynchus australis) from Chaihuin bay, Chile, and the other of clicks of Franciscana dolphins (Pontoporia blainvillei) from San Clemente del Tuyu, Argentina. Our metrics allow a good characterization of each species’ clicks with quick and efficient computation, with good reproducibility across different recording devices, and a clear separation of the two species. We suggest it could be applied to more datasets from different species, and possibly be used to classify NBHF of sympatric species.