BIOACUSTIC

OF MEDITERRANEAN CETACEANS

Acoustic equipment

Cetacean sounds' library

Pilot whale

Sperm whale

ACOUSTIC EQUIPMENT

Towed single and stereo hydrophones: microphones were ceramic piezoelectric sensors; impedance 50kohm; frequency response 3 Hz to 32 kHz. The acoustic signal is recorded both on a digital support (Sony TCD- D100 DAT) and on the computer hard disk using a USB device(Yamaha USB500). The system is measured, optimised and controlled through a real time analyser, SIA SmartLive 5.

IFAW www.ifaw.org cetaceans software was used in order to localize cetaceans during the boat surveys: navigation and data storage were controlled by "Logger 2000"; cetacean's clicks detection were monitored by "Rainbow Clicks" and dolphin's whistles were detected by "Whistle Detector". Real time analysis was performed using SIA SmartLive 5. Post processing was made with SpectraLab and Cool Edit software.

CETACEAN SOUNDS' LIBRARY

Acoustic detections in the study area started since 1995. Unfortunately in 1999 all data were missed except the pilot whale's database. The bioacoustic library restarts in 2000. Today the Delphis collection consists in hundred of recordings of six different species of cetaceans. The following sounds are short samples for each species. Sounds were saved as mp3file to allow a fast downloading.

	45KB mp3file			striped dolphin (Stenella coeruleoalba)
	72KB mp3file			common dolphin (Delphinus delphis)
	83KB mp3file			common bottlenose dolphin (Tursiops truncatus)
	59KB mp3file			Risso's dolphin (Grampus griseus)
	31KB mp3file			pilot whale (Globicephala melas)
	regular clicks 213KB mp3file	codas 99 KB mp3file	chirrups 101 KB mp3file	sperm whale (Physeter macrocephalus)

PILOT WHALE

The opportunity to perform direct and continuous "in situ" observation on a wild pod of long finned whales allowed the authors to brings new insight on some important aspects of their acoustic repertoire. The limited number of individuals of the pod let us to easier isolate the acoustic source and assign calls to whales to demonstrate that whales produced mostly their own signature call.

Spectrograms of the signature whistle of Santiago, an adult male.

Spectrogram of the signature whistle of Cagliostro, an adult male.

Pan, a juvenile male, developed his signature through years.

Signature remains stable over long periods of time and its frequency versus time "contour" shows a high degree of stereotypy. This "contour" might vary in duration, in number of repetitions, some part of it could be deleted, but remain clearly recognizable. Male's individual calls were found to be predominant. At last was possible to document the develop of a signature whistle in a juvenile male of pilot whale since it was 1-2 years old, starting from a simple whistle to arrive a defined call with an introductory and a terminal structure well recognisable.

SPERM WHALE

Since 2002, sperm whale's social groups, composed by females and their immatures, were recorded in the study area.

Sperm whales produced long sequences of regular clicks during long dives (sounds projected by whales in the marine environment in order to obtain information of their surroundings from the echoes they receive).
In addition to the regular sequences of clicks, different types of sounds that are often referred as "social vocalisations" were heard. Their exact function is still unknown. These different types of vocalisation and their characteristics are defined as follows:
"Chirrups": brief rapid trills of 10 - 50 clicks, produced at high rate (220 clicks/s) and lasting for 10-25s. They were described as "social sounds".

Spectrogram of chirrups recorded from the sperm whale social groups

Clicks forming the chirrups appeared to be broad-band, with frequency values ranging
from 1 to more than 22kHz. However, in some cases, a frequency of about 6,5 kHz appeared to be particularly emphasized.

"Squeals": prolonged narrowband sounds with a frequency modulated structure. This unusual vocalisation was recorded only few times. A good example of squeals recorded by us is presented in the spectrogram of Fig. 14. It shows a flat frequency signal with harmonic structure. In some occasions the squeal ended with a down-sweep.
The basic component of the squeal was generally in the region of 7.5 kHz. The squeals analyzed varied in duration from approximately 0.3s to 0.7s, with predominance of the energy in the central and lower harmonics.

Spectrogram of two squeals recorded from sperm whale social groups

From the existing and relatively recent literature, it is generally believed that sperm whale vocalizations are restricted to click type signals.
However, preliminary data here reported provides evidence that sounds other than distinctive clicks are emitted by sperm whales. In particular, from spectrogram comparisons, these sounds appeared to be quite similar to the squeals recorded by Goold (1999) and Drouot (2003).

"Codas" are distinctive stereotyped patterns of clicks. The function of codas is not clear, although they may play a role in acoustic communication with information being coded in the pattern and rhythm of the clicks.

Spectrogram of 3+1 coda pattern

The relative timing pattern - or rhythm - has been used in recent studies to discriminate different coda patterns.
Throughout the world's oceans several different coda patterns have been recorded. Some coda types seem to be common to different areas and for a long time one single coda pattern (3+1) was thought to be the unique coda of the Mediterranean, although other codas has been reported on few occasions.
In our recording, the 3+1 coda pattern is well represented, however several different pattern, suggesting a much wider repertoire, were recorded.