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Prédation du requin-tigre sur le dugong dans le lagon de la Nouvelle-Calédonie

Abstract : We report the recent sighting of a dugong from a small outboard motorboat by flat sea and completely clear sky on August 08, 2021 around 09:00, in the southwestern lagoon of New Caledonia off La Tontouta (22 °06.50'S 166 °07'E). The dugong was lying horizontally below the surface when approached by the motorboat. The left lobe of its caudal fin was almost completely severed, which necessarily diminished its swimming capacity. The dugong was unable to sound, either because its injured caudal fin lacked the power to provide enough momentum, or because of general physiological distress. The main gash on the left lobe, clearly delineated along its entire length, was attributed to a single, powerful bite made by a large shark with homodont sharp teeth. The characteristics of this injury designate its author as a tiger shark, the only large predatory shark of New Caledonia to present this type of dentition. The bottom at a depth of 11 m was clearly visible from the surface. It consisted of gray sandy mud sediment with a sparse seagrass bed. A tiger shark estimated to be 3-4 m in length, recognizable by its blunt snout, its slender silhouette posteriorly and its asymmetrical caudal fin, passed back and forth near the bottom. The latter possibly was responsible for the quasi-severing of the dugong's caudal lobe. The observations made here are reminiscent of a hunting technique observed previously on other large mammals including dolphins and humans, where the tiger shark cautiously approaches its prey from the rear, to promptly inflict a powerful bite intended to immobilize it and then waits for it becoming weak enough to no longer represent a danger to the shark and to devour it. This case is to our knowledge the first to document predation by the tiger shark on the dugong in New Caledonia.
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https://hal.ird.fr/ird-03499045
Contributor : Philippe Borsa Connect in order to contact the contributor
Submitted on : Tuesday, December 21, 2021 - 12:17:20 PM
Last modification on : Thursday, January 13, 2022 - 4:30:27 AM

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Philippe Borsa, Joël Lauvray, Jean-Pierre Morio. Prédation du requin-tigre sur le dugong dans le lagon de la Nouvelle-Calédonie. Bulletin de la Société zoologique de France, Socété zoologique de France, 2021, 146, pp.159-161. ⟨ird-03499045⟩

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