seaturtle.org : MTN : ARCHIVES : Sign In

Marine Turtle Newsletter 110:8, © 2005

Marine Turtle Newsletter-Online

Gladiatorial Attack on a Turtle

Flegra Bentivegna
Turtle Point and Rescue Center Coordinator, Stazione Zoologica Anton Dorhn, Villa Comunale, Napoli 80021, Italy
(E-Mail: flegra@szn.it)

For the last twenty years, at the Stazione Zoologica at Naples, Italy, we have been trying to reduce the mortality rate of the loggerhead turtle population in the central Tyrrhenian sea, especially in spring and summer while in search of food (Bentivegna 1998; Bentivegna et al. 2003). The principal causes of injuries to these animals are entanglement with fishing nets, encounters with motorised boats, both large and small, and small sized refuse thrown into the sea. At the Rescue Centre and Turtle Point, two establishments instituted by the Stazione Zoologica to provide professional help for these animals, we are now curing as many as one hundred turtles per year (Bentivegna et al. in press).

At the beginning of July 2005 we recovered a loggerhead turtle in a serious state of exhaustion which also showed a small wound in the carapace, 1.2 cm wide by 3.7 cm long along the third marginal scute. The turtle, a male measuring 68 cm CCL and weighing 40 kg, had been sighted off the Pontine Islands (or more precisely near Ventotene at 40°48 N, 13°26 E) while it was trying to swim on the
surface with obvious difficulty. After being rescued by some scuba divers, who happened to be in the area, it was quickly transported to Naples and examined by the veterinary staff of the Rescue Centre. To everyone’s surprise it was discovered that inside the small wound and under the carapace there was the end of the broken sword of a swordfish (Xiphias gladius). When extracted it proved to be 23 cm long, approximately one third of the total length of the sword which, for X. gladius is about one third of the whole fish (Tortonese 1975). This would put the overall length of the fish in this case at a little over 2 metres.

The attack of the swordfish on the loggerhead turtle must have occurred several days before as the wound was already partially healed and not bleeding. It is thus possible that it happened much further south, very probably in Sicilian waters. In fact, the Mediterranean swordfish is in a reproductive state from the end of spring until the end of the summer, often in the area of the Strait of Messina (Cavaliere 1962) and the only known previous cases of similar attacks were on two loggerhead turtles near Sicily in August 1999 (Di Natale et al. 2000).

Although we do not have enough evidence to reconstruct the dynamics of this case, one can exclude an intentional attack by the swordfish on the loggerhead turtle and consider a defensive situation. The sword-like bill is believed to be used in such situations for slashing into dense shoals of fish as well as in defence (Nakamura 1986). The swordfish is known to be an aggressive species and
attacks on small boats are often documented. In particular, cases of attacks by Istiophoridae and Xiphiidae on Dermochelyidae and Cheloniidae have been documented outwith the Mediterranean by Frazier et al. (1994) and Eckert et al. (1994). It is certain that in our case the impact must have been of considerable violence to penetrate the carapace of a turtle and break off the leading third of the sword although this fish is pelagic and a very fast swimmer, sometimes
jumping clear of the water (Tortonese 1975).

The turtle was given an antibiotic cure with the addition of vitamins and special treatment of the wound and after only a week had regained its swimming agility and was feeding on small fish and shrimps. At present it is in a tank at the Turtle Point convalescent facility, waiting to be released as soon as possible into its natural habitat.

BENTIVEGNA, F.1998. Caretta caretta: research and rescue program. EAZA Spring Council Meeting in Moscow. EAZA News n.23:14.

BENTIVEGNA F., M. CIAMPA, G. MAZZA, A. PAGLIALONGA & A. TRAVAGLINI, 2003. Loggerhead Turtle (Caretta caretta) in Tyrrhenian Sea: Trophic role of the Gulf of Naples. In: D. Margaritoulis & A. Demetropoulos (editors). Proceedings of the First Mediterranean Conference on Marine Turtles. Barcelona Convention – Bern
Convention- Bonn Convention (CMS). Nicosia, Cyprus.270 pp.

BENTIVEGNA F., M.CIAMPA, G. DE MARTINO, F. MAFFUCCI, R. SCALESSE, S. HOCHSCHEID (in press). Heavy boat traffic threatens loggerhead turtles in south west Italian waters. Second Mediterranean Conference on Marine Turtles Kemer, Antalya, Turkey. 4-7 May 2005.

CAVALIERE A. 1962. Studi sulla biologia e pesca di Xiphias gladius L. Ibid.,XVII (2)

DI NATALE A., G. INSACCO, B. ZAVA. 2000. Casi di predazione su Caretta caretta (Linnaeus 1758) in Mediterraneo centrale. First Italian Meeting on Sea Turtle Biology and Conservation. Policoro (MT)19-20 ottobre.

ECKERT S.A., D. MCDONALD, & P. DUTTON. 1994. Dermochelys coriacea (Leatherback sea turtle) billfish interaction. Herpetological Review 25: 6-64.

FRAZIER J.G., H. FIERSTINE, S.C. BEAVERS, F. ACHAVAL, H. SUGANUMA, R.L. PITMAN, Y. YAMAGUCHI, & C.M. PRIGIONI. 1994. Impalement of marine turtles (Reptilia, Chelonia: Cheloniidae and Dermochelyidae) by billfishes (Osteichthyes, Perciformes: Istiophoridae and Xiphiidae). Environmental Biology of Fishes 39: 85-96.

NAKAMURA I. 1986. Xiphiidae. In: Fishes of the North-eastern Atlantic and the Mediterranean Vol II :1006-1007. Editors P.J.P. Whitehead , M.L: Bauchot, J.-C.Hureau, J.Nielsen, Tortonese E. –UNESCO.

TORTONESE E. 1975. Fauna d’Italia Osteichthyes Pesci Ossei. Ed. Calderini Bologna. 636 pp.