MTN 39:4-7 The Status of Marine Turtles in Senegal

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The Status of Marine Turtles in Senegal

A. R. Dupuy
Service des Parcs Nationaux, Ministere de la Protection de la Nature, Republique De Senegal

[This article was translated from the French with the kind assistance of Denise Volkoff. Any errors of interpretation or fact are those of the Editor, who accepts sole responsibility. NBF]

For a long time, pioneers of research in this region (e.g., people like Cadenat, Villiers, Blanc, Doutre, Dekeyser, Maigret, etc.) accumulated precious data relating to the status of marine turtles. But since then, no further developments have occurred. Today, thanks to the creation of the National Parks in littoral and marine areas, which allows for the constant monitoring of areas favorable to the presence and reproduction of marine turtles, our knowledge of these species has been noticeably enriched. Observations have been made by people walking on the beaches day and night, by others in boats on the high seas, and also from airplanes and helicopters which allows the tracks of turtles having come ashore to be discovered as early as dawn. For ten days surveys were made with the help of IFAN and IUCN-WWF. The results obtained are presented below. Five species have been formally identified as frequenting the beaches of Senegal in order to reproduce.

Green turtle, Chelonia mydas (Linné): Tortue verte or Tortue franche

Generally vegetarian, weighing up to 450 kg. The most common turtle throughout the year in the waters along the coast of Senegal, the green turtle is more abundant where the are important sea grass beds. This species is much appreciated by fishermen for its meat and fat, but also for its eggs. For this reason it is in evident decline in Senegal as well as in tropical seas throughout the world. Turtle soup and a fascination with the turtle shells lead people to exploit the natural populations excessively. In addition, reproduction seems more and more threatened by marine pollution and by beach development, which prevents or severely disrupts the nesting.

According to an inquiry made in 1977 by the Curator of Langue de Barbarie National Park, situated at the mouth of the Senegal River, the capture of marine turtles increases in this region beginning with the onset of the dry season. The drought in the Sahel causes an increase in meat prices in the town markets so that the coastal peoples turn to the turtles in order to meet their needs.

Thanks to the parks along the shores (particularly those of the Langue de Barbarie, the Delta of Saloum, the Kalissaye Reserve) a small population of green turtles may now survive and reproduce in Senegal. In spite of the fact that the species is partially migratory or at least wandering, the time of reroduction has been determined as lasting from January to March and from July to October. In 1985, the largest number of nests were found at Sangomar Point as well as on the little island of sand in Saloum Delta National Park.

Hawksbill turtle, Eretmochelys imbricata (Linné): Tortue à écailles or Tortue tuillée

Carnivorous, frequenting shallow waters and mangroves. This sedentary turtle is much sought for by both fishermen and tourists, and was the least often seen in our investigation. Its rarity probably is linked to over-exploitation. It is present in the littoral areas in Senegal with the greatest numbers occurring to the south of Mbour. No formal observation of nesting was made in our study zone zones. Hawksbills are the smallest of our marine turtles. The measurements given have always been less than a meter, for a weight of about 100 kg for the largest specimen.

Loggerhead turtle, Caretta caretta caretta (Linné) - Tortue caouanne or Tortue jaune

Generally carnivorous and wandering. This yellow turtle is relatively common in pelagic areas and on the coast and is clearly a carnivore. Its large size (more than a meter, for a weight of 400-500 kg) and its obvious coloring render it easily recognized. It is this species in particular that the fishermen catch sight of during their excursions at the level of Dakar far into the sea. Less dependent on the littoral grasses because it feeds on fish, it is more pelagic than the species mentioned previously. Reproduction was observed several times by Cadenat in the Almadies in 1949, and more recently in Langue de Barbarie National Park in January 1982, on the Island of Téréma in Saloum Delta National and also on certain small islands of the Kalissaye Reserve in March 1984. One nest went to term at the Ile of Madeleine National Park on 19 October 1977, yielding 50 hatchlings. The species generally nests from the beginning of the rainy season (July) until October or later. Hatching may occur even into February and March. The species survives better than the green turtle because its meat is little appreciated; however, there is still an active trade in loggerhead shells.

Olive ridley, Lepidochelys olivacea (Eschscholtz) 1829: Tortue olive or Tortue de roches

Probably omnivorous, with a tendency to eat shellfish. This species seems particular to specific regions. This is the nominal form which frequents our coast. The olive turtle frequents most often the shallow waters of the coast and the estuaries, remaining on the bottom. It is present at the extremity of Sangomar Point. Its high relative frequency may be explained by the fact that its flesh is little appreciated by the people of the coast, and the peculiar profile and small size of its shell lead to reduced demand by the tourists and tradesmen. Since attention has been attracted to this species (in particular by our collegague J. Maigret), its status is better known and it is in fact common in the littoral zone.

Table 1. Observations on Marine Turtles In Senegal

Date	Place	Species	Observations
1981	Kalissaye Ornithological Reserve	Chelonia mydas	16 nests
1 June 1985	Isle of Birds (Saloum Delta Nat'l. Park)	C. mydas	3 strandings
10 May 1984	Kalissaye Ornithological Reserve	Eretmochelys imbricata	1 turtle
1984/85	Kalissaye Ornithological Reserve	E. imbricata	Several tracks
22 June 1978	South of Saloum Delta (at the entrance of Bolon de Djinack)	Dermochelys coriacea	7 nests
13-28 Jul. and 12 Aug. 1980	In the north of the Delta de la Casamance	D. coriacea	4 nests
25 Sept. 1985	Sangomar Point	D. coriacea	several eggs - turtle photographed and released
1984/85	Sangomar Point	D. coriacea	1 stranding
27 Jun. 1985	Sangomar Point	?????	1 nest, several eggs
27 Jul. 1985	Kawatt Point	?????	2 nests, eggs not found
29 Jul. 1985	Iles aus Boeufs	?????	4 nests, several eggs (87 eggs eaten by a Nile monitor lizard)
29 Jul. 1985	Iles aux Oiseaux	?????	5 nests, several eggs
30 Jul. 1985	Iles Lébar	?????	7 sites, no eggs or nests located
7 Aug. 1985	Iles Lébar	?????	1 nest, several eggs
7 Aug. 1985	Iles aux Oisseaux	?????	2 sites, neither had eggs
2 Sept. 1985	Sangomar Point	?????	several eggs
7 Sept. 1985	Sangomar Point	?????	1 site, several eggs
11 Sept. 1985	Sangomar Point	?????	1 nest, several eggs
1 Nov. 1985	Sangomar Point	?????	1 nest, several eggs

Leatherback turtle, Dermochelys coriacea (Linné): Tuortue luth or Tortue cuir

The leatherback is the largest of all since its weight may surpass 600 kg and its size approach 2.5 m. It is frequent in the waters of Senegal in the regions of Sangomar and Saloum, and equally on the Langue de Barbarie. This strictly pelagic animal is above all an eater of jellyfish medusea and comes to the coast only at the time of reproduction. Nesting or nests are rarely observed in Senegal. A nest was observed at the extremity of Sangomar in Djifére in August 1979, and also in February 1962 at Palmarin. On 11 March 1963, some 50 baby turtles were counted at Palmarin. Since 1977, leatherbacks have only been observed at sea, but the capture in Joal of a "marine monster," the stranding of an adult leatherback in Langue de Barbarie National Park and of another one in Kalissaye in Bird Island in Saloum Delta National Park and at Sangomar Point by Kayar and Hann during this last year witness its regular presence in our waters. Finally, a female in the process of laying on Sangamor Point in 1985 was photographed, illustrating that the sector may still be priviledged by visits of this rare species. The laying of 180 eggs, their hatching, and the observation of the babies going to the sea was a success, joy and comfort for all the conservationists. Other nestings have been indicated in recent years (see Table 1, previous page).

The very serious threat which is directed toward this species comes from marine pollution and disposal at sea of plastics which are ingested by the turtle, mistaking them for the jellyfish that are its natural prey. Humans generally capture leatherbacks only by accidental netting, since its meat is little valued or even rejected since it is considered almost venomous. However, there remains the problem of consumption of eggs, which are very much sought by the natives on the shore.

In conclusion to the analysis of the threatened marine turtles, it remains urgent that the laws aiming to protect them be strictly applied in Senegal, particularly regarding the sale of their shells. It is worthy of note that a minimum of 200 nestings were observed on the coast in the 1950's, about 10 per year were seen in years after 1950. About 20 were observed in 1985.

Brief Bibliography

Brongersma, L. D. 1968. Notes upon some turtles from the canary Islands and from Madeira. Koninkl. Nederl. Akademic van Weltenschappen. Amsterdam. Proceedings, Series C, 71(2):128-136.

Pritchard, P. C. H. 1967. Living Turtles of the World. TFH Publications.

Bustard, R. 1972. Sea Turtles: Their Natural History and Conservation. Collins. London.

Cadenat, J. 1949. Notes sue les tortues marines des cotes du Sénégal. Bull. IFAN 11 (1 & 2(:16-35.

Maigret, J. 1975. Notes faunistiques I. Les tortues de Banc d'Arguin. Bull. Labo. Peches, Nouadhibou No. 4, December 1975:116-118.

Maigret, J. 1977. Les tortues de mer du Sénégall. Bull. Ass. Avanc. Sc. Nat. Sénégall. 59, October 1977:7-14 + 2 Fig.

Maigret, J. 1978. Sea turtles nesting on the coast of Sengal. MTN 8:4.

Maigret, J. 1983. Répartition des tortues de mer sur les cotes ouest African Museé Océanographique, 3 July 1983.

Villiers, A. 1958. Tortues et crocodiles de l'Afrique noire française IFAN. Initiation Africaines XV 1958.

Villiers, A. 1978. Tortues et crocodiles de l'Afrique noire française. Africaines, No. 5, IFAN, Dakar.