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Marine Turtle Newsletter 135:19-20, © 2012

Marine Turtle Newsletter-Online

New Northern Limit of Nesting of Lepidochelys olivacea in the East Atlantic Ocean: North Senegal (West Africa)

Jacques Fretey1, Assane Ndoye2 & Arona Fall2
1Centre de recherche sur les tortues marines, Chélonée, Mas du Ringué, 46260 Beauregard, France (E-mail: jfretey@imatech.fr);
2Parc national de la Langue de Barbarie, Sénégal (E-mail: ndoyeassane68@yahoo.fr; fallarona@hotmail.com)

The Langue de Barbarie National Park in Senegal was created in January 1976. It is a long dune strip about 15 km in length and 1 km wide, between the Senegal River and the sea. Green turtles (Chelonia mydas) nest sporadically on this long beach (Fretey 1990). On the morning of 21 June, 2011, a fisherman discovered tracks of a turtle that he did not recognize on the beach within the national park (15.986944 °N, -16.513611 °W). The guards of the park were informed, and they left the nest in situ with a wire fence protecting it. Fifty-five days later, 112 hatchlings emerged, and the hatchlings were identified by one of us as Lepidochelys olivacea (Eschscholtz, 1829). Overall success rate of this nest was 98% (out of 117 total eggs laid). This case marks the northernmost known for this species in East Atlantic Ocean.

The distribution and nesting of Lepidochelys olivacea in West Africa sensu stricto are still poorly know (Fretey 2001; Varo-Cruz et al. 2011). Maigret (1983) estimated that the northern limit of this species in the East Atlantic was Senegal. However, the collection of the Institut Fondamental d’Afrique Noire (IFAN) in Dakar has a ridley turtle (accession number 55.32.136) collected in 1955 from Port-Étienne (now called Nouadhibou) in Mauritania (nearly 21°N). Interestingly, Carr (1957) reported that the most northerly limit for olive ridleys in the East Atlantic Ocean was 21°N. Arvy & Dia (1997) reported the existence of olive ridley carapaces in Mauritania, and recently, news cases of olive ridleys were observed South of the capital Nouakchott (Mint Hama et al., in press). To date, there has been no confirmation of nesting by olive ridleys in Mauritania.

In terms of nesting in Senegal, Cadenat (1949) reported the capture of two immature olive ridley turtles in nets sharks off of Hann beach in Senegal, and suggested that they could have originated from nests laid on beaches near Dakar, Gorée, N’Gapara and Joal (Cadenat, 1957).

The Sea Museum of Gorée Island holds in its collection one olive ridley hatchling it remains unclear whether it came from nest laid on a Senegalese beach (Fretey 1998). Maigret (1977) posited that olive ridleys may possibly nest on the coasts of Senegal, and a 1982 report of the Direction of the National Parks of Senegal suggested that the species is likely to reproduce within the limits of protected area of the Delta of Saloum. However, the record we report here is the first confirmed nest of olive ridleys in Senegal.

Within the central Atlantic Africa region, there is confirmed nesting of olive ridleys on several islands in Guinea-Bissau. The highest density nesting site in the region appears to be on the islands of Orango Large, Imbone, Adonga and Orangozinho in Orango National Park of the Archipelago of Bijagos (Catry et al. 2009). Fretey & Malaussena (1991) noted olive ridleys nesting further south, in Sierra Leone, on the small island of Baki, within the archipelago of Sherbro – Turtle Islands. We recommend that sea turtle researchers in the region be vigilant in observing and reporting the occurrences of this species, to help illuminate more precisely their nesting and foraging distribution.

Acknowledgements. Thanks to Patrick Triplet and Laurent Joubert for their assistance in this discovery.

ARVY, C., & A. T. DIA. 1997. Données sur les tortues marines et sur la tortue terrestre du littoral mauritanien. In: F. Colas (Ed.). Environnement et Littoral Mauritanien. Actes du Colloque, 12-13 Juin 1995, Nouakchott, CIRAD, Pp. 101-104.

CADENAT, J. 1949. Notes sur les tortues marines des côtes du Sénégal. Bulletin de l’Institut Fondamental d’Afrique Noire 11:16-35.

CADENAT, J. 1957. Observations de cétacés, siréniens, chéloniens et sauriens en 1955-1956. Bulletin de l’Institut Fondamental d’Afrique Noire 14: 1358-1375.

CARR, A. 1957. Notes on the zoogeography of the Atlantic sea turtles of the genus Lepidochelys. Revista de Biología Tropical 5:45-61.

CATRY, P., BARBOSA, C., PARIS, B., INDJAI, B., ALMEIDA, A., LIMOGES, B., SILVA, C., & H. PEREIRA. 2009. Status, ecology and conservation of sea turtles in Guinea-Bissau. Chelonian Conservation and Biology 8:150-160.

FRETEY, J. 1990. Rapport préliminaire d’expertise sur le statut des tortues marines au Sénégal. Unpublished report, IUCN-Délégation Régionale en Afrique de l’Ouest, 16 pp.

FRETEY, J. 1998. Marine Turtles of the Atlantic Coast of Africa – Tortues Marines de la Façade Atlantique de l’Afrique. UNEP/ CMS Technical Publication 1, 254 pp.

FRETEY, J. 2001. Biogeography and Conservation of Marine Turtles of the Atlantic Coast of Africa. Biogéographie et Conservation des Tortues marines de la Côte atlantique de l’Afrique. CMS Technical Series Publication no 6. UNEP/CMS Secretariat, Bonn, Germany. 429 pp.

FRETEY, J. & J. P. MALAUSSENA. 1991. Sea turtle nesting in Sierra Leone, West Africa. Marine Turtle Newsletter 54:10-12.

MAIGRET, J. 1977. Les tortues de mer au Sénégal. Bulletin de l’Association pour l’Avancement des Sciences Naturelles au Sénégal 59: 7-14.

MAIGRET, J. 1983. Répartition des tortues de mer sur les côtes ouest africaines. Bulletin de la Société Herpétologique de France, 28 : 22-34.

MINT-HAMA, L., J. FRETEY & M. AKSISSOU. In press. Nouvelles données sur le statut des tortues marines en Mauritanie. Proceedings of the Deuxième Congrès Méditerranéen d’Herpétologie. Bulletin de la Société Herpétologique de France.

VARO-CRUZ, N., P. LOPEZ, J. COZENS, A. LIRIA-LOZA, J. FRETEY & L. F. LŌPEZ-JURADO. 2011. New records of olive ridley sea turtle (Lepidochelys olivacea) in Cape Verde Islands. Zoologia Caboverdiana 2 :53-61.