Finding of a dead rough-toothed dolphin Steno bredanensis (Cuvier and Lesson, 1828), stranded on the south Morrocan coast

Abstract

The rough-toothed dolphin Steno bredanensis (Cuvier and Lesson, 1828) inhabits tropical and warm-temperatures seas. However, in many of these places, the specie has not been recorded yet, so the distribution is based on scarce watching and stranding data. There are so few data of this species from around the world that the International Union for the Conservation of Nature (IUCN) catalogues this animal with Insufficiently Known status, which makes any observation of this species extraordinarily valuable. Most of the encounters with the rough toothed dolphin have taken place offshore (Addink & Smeenk, 2001; Ritter, 2002). Though there are records of shallow water watching, often associated with feeding behavior (Delgado Estrella, 1994), individual OR SINGLE stranding is not very common (Smeenk, pers. com.) but often they strand in groups (massive stranding) (Cadenat, 1949; Stinnintz et al., 2000; Manasijevic et al., 2002). Between the 4 and the 11 of September 2002 we took part in an expedition through the western coast of Morocco and the Western Sahara (De los Rios y Ocana, in prep.) searching for sea turtle nesting evidences and feeding ecology data. During this expedition, we found a rough-toothed dolphin Steno bredanensis, dead for several weeks. We would like to present here the results of our identification and study of the specimen. The coast of Tarfaya consists of a large sandy beach, full of sediments and debris due to strong currents. Almost any inert material is, therefore, washed ashore. Much plastic debris such as bags, bottles, etc., and even three hulks, stranded in less than half a mile, were found in the littoral area. From our starting point (waypoint N 27o 55 163 W 012o 53 048 ), walking to either side of the beach for about 2 km, we found two Loggerhead turtle (Caretta caretta) carcasses, one Common dolphin (Delphinus delphis) corpse, and another corpse later identified as a Rough-toothed dolphin, Steno bredanensis (Fig. 1). So, according to our observations and also to local fishermen, this long and sandy coast is an area where cetaceans and turtles usually strand throughout the year. Identification of a dolphin which is alive, recently stranded or dead for just a few days, is not very difficult, especially for experts. Unfortunately, most of the times, we find the animal many days after death, lying on the beach, burnt by the sun, and even with some showing. In these cases, we have to perform anatomical analysis in order to make a proper identification, and the best part to do that on the skull, where the most differential characteristics are concentrated. The carcass in question presented a level of putrefaction 3, as the skin was totally dry and petrified. The identification of the specimen turned out