Sperm whales from the Tethys photo-ID catalogue to a mass stranding: a 2000 km journey across the Mediterranean

In december 2009, a unusual mass stranding of sperm whales occurred along the coast of the Gargano Promontory, Adriatic Sea. Three out of the seven stranded whales had been previously photo-identified; two of them had been catalogued by Tethys in the Ligurian Sea.
The good news is: one further individual from Tethys-Ligurian Sea was re-sighted in the Hellenic Ionian Sea - safe and sound.
This provided some new insight in male sperm whales' movement patterns across the Mediterranean basin, as shown in a recently published paper.

ITALIANO
Nel dicembre del 2009 si verificò un insolito spiaggiamento di massa lungo le coste del Gargano, in Adriatico. Dei sette capodogli spiaggiati, tre erano stati foto-identificati precendentemente; due di questi erano stati catalogati da Tethys, in Mar Ligure.
Una buona notizia è che un altro individuo di Tethys-Mar Ligure è stato riavvistato nello Ionio ellenico - vivo e vegeto.
In questo modo è stato possibile documentare per la prima volta i movimenti dei maschi di capodoglio nel bacino mediterraneo, come viene descritto in un lavoro scientifico pubblicato recentemente.


A. Frantzis, S. Airoldi , G. Notarbartolo di Sciara , C. Johnson , S. Mazzariol
Inter-basin movements of Mediterranean sperm whales provide insight into their population structure and conservation.
Deep-Sea Research I 58 (2011) 454–459

Abstract
The sperm whale is one of the very few deep diving mammal species in the Mediterranean Sea. Following a rare mass stranding of male sperm whales in the Adriatic Sea in December 2009, photo- identification methods were used in order to investigate previous sightings of the stranded whales in the region. Fluke photos of the stranded whales were compared with those of 153 and 128 free-ranging individuals photographed in the western and eastern Mediterranean basins, respectively. Three out of the seven stranded whales had been previously photo-identified and some of them more than once. To reach the stranding place, two of these re-identified whales performed long-range inter-basin move- ments of about 1600–2100 km (in a straight line) either through the Strait of Sicily or the Strait of Messina. In addition, comparisons among all whales photographed in the two Mediterranean basins revealed that one more individual first photographed in the western basin (1991) was re-identified 13 years later in the eastern basin (2004). These three cases provide the first conclusive evidence of inter- basin movement of sperm whales in the Mediterranean Sea. Inter-basin gene flow is important for the survival of the small and endangered Mediterranean sperm whale population. Mitigating the disturbance created by human activities in the straits area is crucial for its conservation.

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