Università degli Studi di Pavia

Centro Interdisciplinare di Bioacustica e Ricerche Ambientali

Via Taramelli 24 - 27100 Pavia - Italy
e-mail : cibra@unipv.it

The voices of marine mammals of the Mediterranean Sea

The cetacean species regularly inhabiting the Mediterranean Sea [read more] produce sounds that can be separated in few simple categories.
The low frequency sounds (around 20 Hz) produced by fin whales; the series of clicks that sperm whales emit with a rhythm of 1-4 per second while diving; the modulated high frequency whistles (ranging in frequency to more than 20 kHz) and the echolocation clicks emitted by small dolphins; and finally the low frequency whistles produced by pilot whales.
Other than sounds produced with specific organs, cetaceans can also produce acoustic signals with parts of their own body. The "tail-slap", the hit of tail on the water surface, is one of the most common behaviours and produces a recognizable acoustic signal; some types of jump in which the animals hit the surface with a large part of their body; the "jaw-clap", produced by some dolphin species by quickly shutting the jaw. The importance of these behaviours is still difficult to understand, though they should have a meaning and a role in the life of those animals.

Sounds are shown here by using spectrograms, special graphs that show the features of a sound, even those our ears can't perceive.
Links to .wav files allow to hear the sounds. By clicking on a sound link the file is downloaded to your computer to be played with your default player. If you prefer to download the file without opening a player, click with the right button and choose the download option (Save Object...). Files have been converted to mono and resampled to 44.1kHz (most of the original recordings are stereo, either 48kHz or 96kHz). For each link the file size is shown; to reduce filesize and download time the files are also available in MP3 format (lowest compression, maximum quality).

All spectrograms and sounds are Copyright of CIBRA and cannot be used/distributed/published without a written permission from CIBRA.

Bioacoustic research in the Mediterranean Sea

Acoustic research in the Central Mediterranean Sea has developed mostly during the last decade. Though, the first recordings of cetacean sounds we know of were made by W.A. Watkins and W.E. Schevill in 1958; they recorded the pilot whale Globicephala melas and samples of that recordings are included in the Marine Mammal Sound Database at the Woods Hole Oceanographic Institution (WHOI).
The first attempt to apply systematic modern bioacoustic methods was made in 1985 by Watkins and colleagues. The data gathered during their cruise in the Sicily Channel confirmed the value of underwater sound as a tool for determining the presence of cetacean species, even in otherwise prohibitive meteorological conditions. Watkins and his team heard and recorded many well known species from that area as well as the rare rough toothed dolphin Steno bredanensis. This cruise was the incentive for further research, and Notarbartolo di Sciara and colleagues from Tethys Research Institute (Milan, Italy) started their first acoustic campaign "Listen to the whale" on the open sea in summer 1987. At the same time Azzali and colleagues from the National Research Council at Ancona, Italy, designed scientific studies to be carried out with captive bottlenose dolphins into their target detection capabilities.
Bioacoustic research at the University of Pavia began in 1983; activities were initially addressed at developing instruments and software for digital sound analysis and in 1987 the first digital spectrograms of striped dolphins' and Rissos' dolphins' sounds were made.
The “Centro Interdisciplinare di Bioacustica e Ricerche Ambientali” (CIBRA) of the University of Pavia was founded in 1989 with a special section devoted to "Marine bioacoustics" to carry out extensive research on the acoustic communication in marine mammals of the Mediterranean Sea. It now has a Cetacean Sound Library with hundreds of hours of high quality underwater sound recordings. The very first years of activity were devoted to setup state of the art equipment and to carry out research cruises on board of small motorsailing boats. In 1994 an international workshop was organized in Erice, Sicily, on the topic of underwater bioacoustics to focus on emerging research themes such as the impact of noise and the use of advanced passive acoustic techniques to monitor marine mammals.
Within the European Nature Conservation Year 1995 (ENCY95), the Italian Navy set up a cooperative research program with Universities and other institutions to give logistic support and to apply its technologies to the study and protection of the marine environment. The program included a research on cetacean acoustics, mainly dealing with the two larger species in the Mediterranean Sea, the fin whale Balaenoptera physalus and the sperm whale Physeter macrocephalus. Recordings made by different platforms, such as surface vessels, submarines and sonobuoys were collected and analyzed to be included in the Cetacean Sound Library at CIBRA. Particular emphasis was put into tuning protocols for data interchange and into coordinating efforts for the development of shared methodologies and instrumentation. Training activities were also made to instruct the operators to pay attention to biological sources and to coordinate their efforts in recording them while performing their institutional patrolling activities.
The program demonstrated that the acquisition of biological sounds and information can be carried out side to side with the institutional patrolling activities of the Navy. The results gained so far show that "Dual Uses" of military technologies can be used to solve scientific problems and to provide new valuable information to biologists.

In recent years marine bioacoustic studies have revealed a new emerging problem, the noise impact issue, related with the noise produced underwater by human activities such as navigation, military operations, military sonar use, seismic surveys, and also coastal and offshore platforms. The “acoustic pollution" is a new kind of pollution that can affect the well-being of both fishes and sea mammals, decreasing their auditory ability, disturbing the reproductive behaviours or pulling away the animals from their habitats.

A big improvement in research activities was then made possible by the development of the SOLMAR Project headed by NURC, by grants from the Office of Naval Research for the Project "Bioacoustic characterization of the Mediterranean Sea", by the cooperation with international agencies and institutes for the development of mitigation policies and tools to reduce the impact of anthropogenic noise on marine mammals and by the cooperation with other international projects such as NEMO.

Recent advances are described in the pages on the current research projects.

CIBRA Home Page

Created June 2005, updated August 2005