Università degli Studi di Pavia

Centro Interdisciplinare di Bioacustica e Ricerche Ambientali

Ziphius, a project about a poorly known endangered species

Ziphius cavirostris is a pelagic, deep-diving species and the only beaked whale commonly found in the Mediterranean Sea. The species was described by G. Cuvier, as a fossil, using a partial skull collected in 1803 near Fos-sur-Mer, on the Mediterranean coast of France (Cuvier, 1823). Beaked whales generally live offshore often associated with regions characterized by canyons or steep escarpments.
In recent years, sightings of Z. cavirostris have been reported more frequently in some areas, such as the Ligurian Sea, where studies concerning habitat use and diving behaviour were also carried out (Azzellino et al., 2003; Johnson et al., 2004).
In recent years, mass strandings of this species appeared to be associated with naval activities with use of high power sonars (Simmonds and Lopez-Jurado, 1991; D’Amico (ED), 1998; Frantzis, 1998 and 2004; Evans and England, 2001; Martín, 2002; Freitas, 2004; Martín et al., 2004, Fernàndez et al., 2004).

Assessing and mitigating such impacts is currently limited by the lack of scientific knowledge of beaked whales physiology, behaviour, distribution, and habitat use. A keypoint in mitigation strategies is the ability to detect the animals, by either visual of acoustic observations, or by both. CIBRA is mainly interested in developing and tuning PAM (Passive Acoustic Monitoring) equipment and software to make the acoustic detection of beaked whales possible and efficient.

Acoustic detection of Cuvier's beaked whales

Z. cavirostris is an elusive species whose acoustic signals remained unknown till last year when a team of Woods Hole Oceanographic Institution, headed by Peter Tyack, attached a sophisticated recording tag on the back of several animals. The tag, named D-TAG, attached by suction caps, is able to record the movements of the animal together with the sounds it receives and the sounds it emits. For the first time it was possible to record their sounds and to characterize the Z.cavirostris diving profile. The results clearly explain why those sounds have been never recorded with hydrophones deployed close to the sea surface.

Z.cavirostris emits sounds only at depths greater than 400-500 meters; the sounds are short ultrasonic pulses centered at about 40 kHz (range 20-60 kHz) and emitted with at intervals of about 400ms. As they are high in frquency and emitted at great depth, they reach the sea surface with very little energy and are impossible to detect with standard gear working up to 20 kHz only.

The aim of our study was to broaden the knowledge related to Cuvier’s beaked whales, to characterize their habitat, and to remotely record their acoustic signals by developing suitable equipment.

In late September 2005 CIBRA carried out a bio-acoustic survey during an extensive NURC (NATO Undersea Research Center, La Spezia, IT) research campaign (Zifio ’05) in the Ligurian Sea. The CIBRA team was on board a 12 meter catamaran, named Krill, with its own equipment based on a high quality towed array equipped with a newly designed low-noise front-end featuring digital recording and real-time spectrographic displaying with a nearly 90 kHz bandwidth.
During the cruise, two animals were sighted immediately before diving. No other animals were observed before and after this sighting. The boat was stopped and the engines turned off. The array sank more than 40 meters, but still not in a vertical stand due to strong drifting conditions. A few minutes after the animals started diving, high frequencies click trains were noticed on the real-time spectrograms (SeaProUltra, two channels, 96 kHz bandwidth). Later analyses on the recorded files showed click series with features matching the description given by Johnson et al., 2005.
Frequency center, bandwidth, waveform, repetition intervals and amplitude variations related to head scanning movements confirm that recordings captured the emissions of two Ziphius cavirostris.
This result is relevant for setting up equipment needed for mitigation procedures where the presence of Cuvier’s beaked whales must be estimated and to monitor critical habitats for this species.

This cruise was carried out within the NURC - NATO Undersea Research Center SOLMAR project. We acknowledge ONR Office of Naval Research for having funded the development of the equipment. NURC website: http://nurc.nato.int ; SOLMAR website http://solmar.nurc.nato.int

Mediterranean-wide database and GIS of Cuvier's beaked whales' strandings

Much of the current knowledge of this species has been derived from stranding data. Historically, stranding data in the Mediterranean Sea has been collected by individual researchers, and more recently, over the last two decades, by national stranding networks. In cooperation with the Natural History Museum of Milan and other organizations, an extensive review of stranding data collected by stranding networks from Italy, Greece, Spain, and France has been made. Results were completed with information gleaned from the literature, personal communications, regional newspapers, and the world wide web from the countries that border the Mediterranean Sea. While this review is certainly not exhaustive, it has allowed the creation of an extensive geo-referenced basin wide database using a geographic information system (GIS) of over 300 stranding events. The acquired data permit documentation of the number of mass stranding events, allow general observations about distribution and chronology of stranding events dating back to 1803, and enables evaluation of strandings based on several different criteria.

Podestà M., A. D’Amico, G. Pavan, A. Drougas, A. Komnenou and N. Portunato; A Review of Ziphius cavirostris (G. Cuvier, 1823) Strandings in the Mediterranean Sea. . J. CETACEAN RES. MANAGE. 7(3): 251–261.

This paper has been published on a Special Issue of the Journal of Cetacean Research and Management entirely concerned with Beaked whales.

The research project has been developed in coordination with the NATO Underwater Research Center (SOLMAR Project), with the cooperation of the Italian Navy, of the SPAWAR Center (San Diego, US), of the Natural History Museum of Milan (Italy) and of the Centro Studi Cetacei (CSC).

GIS map of strandings of Ziphius cavirostris recorded in the Mediterranean Sea since 1803.
Strandings of two animals are marked in yellow; mass strandings of three or more animals are marked in red.

ONR Grants N00014-99-1-0709, N00014-02-1-0333, and N00014-03-1-0901

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Updated Novembert 2006