seaturtle.org : MTN : ARCHIVES : Sign In

In the Mediterranean sea, mass cold stunning episodes have never before been recorded although similar events occur in the Atlantic Ocean and Gulf of Mexico (Brongersma 1982; Meylan 1986; Morreale et al. 1993; Witherington & Erhart 1989).

The loggerhead turtles, 35 alive and 20 dead, were discovered and collected by field officers of the Capitaneria di Porto. It was evident that the stranded turtles were affected by the cold water. They were debilitated, moved lethargically and made feeble attempts to dive. Others floated. Carapace, plastron and in some cases the head and the beak of almost all turtles were covered with barnacles, and showed lesions suggesting mycotic infections. All live turtles were housed at the Institute for the Study of Coastal Ecosystems (National Research Council, CNR) of Lesina and tagged by collaborators of the Centro Turistico Studentesco (CTS). Most of the turtles weighed between 5 and 11 kg (mean = 9.3 kg) and only 2 individuals with larger body masses of 25.1 kg and 40.0 kg, respectively, were found (figure 2). The curved carapace length (CCL) ranged from 19.8 to 67.1 cm (mean= 41.7 cm). From these data it can be concluded that all but the largest turtles were definitely immature.

Figure 1. Strandings of cold stunned loggerhead turtles concentrated on a ca. 60 km long coastline between the Fortore river and the head of the Gargano peninsula. Arrows indicate prevailing currents.

Figure 2. Frequency distribution of body mass of the stranded loggerhead turtles (n = 31).

On January 13th 2002, 18 of the rescued turtles were transferred to the Stazione Zoologica "Anton Dohrn" of Naples. They were kept in individual tanks with water of the prevailing temperature of the Gulf of Naples (15-17°C in January/February) and fed with anchovies. During the first month after the incident all turtles, except 2 which are under special medication, fed on average between 5 and 13 g per kg body mass each day. This can be considered as a normal feeding behaviour at this temperature range compared to food intake rates of other non-cold-stunned turtles which were housed in the Stazione Zoologica during the same period (F. Bentivegna personal observation). The turtles which had remained in Lesina were subsequently transferred to other host institutions: another 11 turtles were brought to Naples, 6 were taken by the World Wildlife Fund of Policoro-Herakleia and 4 were hosted by Oasi Blu of the Comune di Sperlonga.

At the time of writing almost all turtles seem to have recovered from the event. Two turtles died, one had ingested a fishing line, with the hook still attached, which lead to the convulsion of the whole intestine; the other one had a blood cystis in the lung. Most of the other turtles have commenced feeding and gained body mass accordingly. However, the extension of the myotic infections and the wounds, which are still not completely healed, require constant treatments. The group of the Zoological Station in Naples, including a veterinarian, is currently combating the mycosis using a purpose designed treatment regime. The aim is to release successfully rehabilitated turtles in May 2002 when the water temperatures have reached at least 18°C.

It is generally known that the cold stunning events happen when inshore marine turtle populations cannot avoid a sudden drop of temperature (George 1997). The water temperatures in the Adriatic Sea remained high with average values between 19 - 21°C until 30 Oct 2001. Then in the following period temperatures dropped to between 11 and 15°C until 20 Dec 2001 (NOAA - CIRES Climate Diagnostic Center, <http://www.cdc.noaa.gov/>). During the cold stunning period the water temperature in the area of the strandings was around 8.5°C (CNR Lesina).

It is possible that before the onset of the cold front some turtles were resident in the area while others originated from more northern regions. Indeed, the drop of water temperatures to critical values initiated in the North Adriatic Sea. In addition to this, the convergence of two currents in direction of the north coast of Gargano (one descending southwards along the Italian coastline and another crossing the Adriatic sea from the Dalmatian coast) may have contributed to the extraordinary number of strandings. In fact, the Gargano promontory protrudes across the Adriatic sea along an E-W axis. Thus the northern shore of Gargano intercepts everything in the sea which the prevailing NE and NNW winds blow southwards (figure 1). In this way turtles, already affected by low temperatures and unable to swim, may have been drifted passively by the current southwards were they were finally recovered.

Whatever the origin of these turtles, this event has shown the residence of immature loggerhead turtles during the winter in the Western Adriatic Sea. Previous surveys of stranded sea turtles have never, with single exceptions, reported turtles in this area during the winter months (Affronte & Gavanelli 2001; CSC 2000; 2001).

Acknowledgements: The transport and housing of the turtles was carried out under permission of CITES. We would like to thank the officers of the Capitaneria di Porto and the following persons, in alphabetical order, for their great effort and assistance: Mario Cacciapuoti, Giuseppe Cancelliere, Mariapia Ciampa, Raffaele D'Adamo (CNR Lesina), Isabella D'Ambra, Luigi Ferretti, Fulvio Maffucci, Gianfranco Mazza, Angela Paglialonga, Andrea Travaglini, and Gianluca Treglia and Luigi Valerio from the WWF Oasi Blu.

AFFRONTE, M. & D. GAVANELLI. 2001. Analysis of stranded sea turtles in the north-western Adriatic Sea. Zoology in the Middle East 24:101-108.

BRONGERSMA, L. 1982. Marine turtles of the eastern Atlantic Ocean. In: K.A. Bjorndal (Ed.). Biology and Conservation of Sea Turtles. Smithsonian Institute Press, Washington D.C. pp.407-416.

CENTRO STUDI CETACEI. 2000. Tartarughe marine recuperate lungo le coste italiane. In: F. Bentivegna (Compiler) I Rendiconto 1998 (Reptilia). Atti Società Italiana Scienze Naturali Museo civico Storia Naturale Milano 141:145-158.

CENTRO STUDI CETACEI. 2001. Tartarughe marine recuperate lungo le coste italiane. In: F. Bentivegna (Compiler) II Rendiconto 1999 (Reptilia). Atti Società Italiana Scienze Naturali Museo Civico Storia Naturale Milano, in press.

GEORGE, R.H. 1997. Health problems and diseases of sea turtles. In: P.L. Lutz & J.A. Musick (Eds.). The Biology of Sea Turtles. CRC Press Inc., Boca Raton, pp. 363-385.

MEYLAN, A. 1986. The riddle of the ridley. Natural History 95:90-96.

MORREALE, S.J., A.B. MEYLAN, S.S. SADOVE & E.A. STANDORA. 1992. Annual occurence and winter mortality of marine turtles in New-York waters. Journal of Herpetology 26:301-308.

WITHERINGTON, B.E. & L.M. EHRHART. 1989. Hypothermic stunning and mortality of marine turtles in the Indian River lagoon sisytem, Florida. Copeia 3:696-703.