Surveys of the sea turtles of Angola

Biological Conservation 58 (1991 ) 19-29

Surveys of the Sea Turtles of Angola

T h o m a s C a r r & Nico le C a r r

Route 2, Box 905, Micanopy, Florida 32667, USA

(Received 27 June 1990; revised version received 16 November 1990; accepted 6 January 1991)

A BSTRA CT

Five species of sea turtles have been reported from Angola (in decreasing order of abundance):, leatherback Dermochelys coriacea, olive ridley Lepidochelys olivacea, green Chelonia mydas, loggerhead Caretta caretta, and hawksbill Eretmochelys imbricata. All have been reported to nest on Angolan beaches, although with varying frequency. Immature, subadult and adult sea turtles have been recorded foraging along the coastline of Angola and in bays which provide developmental habitats. Few data are available on the distribution and abundance of each species in these habitats.

The level of exploitation of turtles in Angola is moderate, as no dedicated turtle fishery exists. If, however, exploitation is considered to include those turtles taken by incidental catch, it would be deemed heavy. All size classes of turtles and eggs of some species have been taken incidentally although it has been reported that eggs are deliberately hunted. Even though sea turtles have been protected under Angola's hunting laws since 1972, and a heavy fine has existed since that time to discourage exploitation, little enforcement has occurred.

I N T R O D U C T I O N

Limited information is available concerning the distribution and abundance of sea turtles in West Africa. Mozambique, Madagascar and Angola have extensive sea turtle populat ions but require more encouragement and assistance (Hughes, 1982). Recent information about the presence and nesting of the various species of sea turtles along the west coast o f Africa is very scarce (Brongersma, 1982). Limited information is available on sea

19 Biol. Conserv. 0006-3207/91/$03'50 © 1991 Elevier Science Publishers Ltd, England. Printed in Great Britain

20 T. Cart, N. Cart

turtle nesting on inhabited coastal areas of West Africa, particularly in uninhabited areas (Fretey & Girardin, 1988). Five species have been documented to occur in Angola. The leatherback Dermochelys coriacea has been reported south of Luanda (Hughes et al., 1973) and nesting (Huntley, 1978). Leatherbacks have been reported along the coast of Angola 'by direct observations or by the presence in collections of hatchlings (or specimens taken from the eggs)' (Brongersma, 1982). The olive ridley Lepidochelys olivacea has been reported in Ambrize (Brongersma, 1961) and in Luanda (Hughes et al., 1973). The green turtle Chelonia mydas has been reported to occur in Cabinda and Luanda (du Bocage, 1866, 1895) and Bahia dos Tigres (Monard, 1937), formerly nesting frequently in Angola but now rare (Vilela, 1923 in Monard, 1937). This species has also been reported nesting south of Luanda (Hughes et al., 1973). The loggerhead Caretta caretta and hawksbill Eretmochelys imbricata have also been reported in Angola (Hughes et aL, 1973).

Little more than documentation of the occurrence of a particular species in Angolan waters or on Angolan nesting beaches has been accomplished since the beginning of this century. During two visits to Angola, our goals were to verify which species of sea turtles occurred there, and to make an assessment of the distribution and abundance of each.

METHODS

Interviews

An exhaustive program of interviews was carried out in the main coastal settlements around Luanda, in Cabinda, and elsewhere along the coast wherever turtles were being captured. Previous experience has shown that in the limited time-frame of an initial sea turtle survey, systematic, multiple interviews are often the most productive and reliable source of information. The interview protocol followed was that of Carr et al. (1982).

Nesting beach surveys

The most direct procedure used in the investigation, and the one that yielded the most useful quantitative information, was a series of aerial and/or ground surveys of all ocean beaches along the Angolan coast, from Quicombo to the northern border of Cabinda (Figs 1-3). These surveys provided data on nesting distributions and densities at that time. Initial counts were made during aerial overflights. A Piper Cherokee 6 fixed-wing aircraft and an Alouette III helicopter were used in surveying beaches from

Sea turtles in Angola 21

Quicombo to the Rio Zaire. The coastline of Cabinda was surveyed in a Bell 206-L helicopter. Observations were more easily confirmed from helicopters which can fly slower than fixed-wing aircraft and can land almost anywhere. When logistically possible and where overflights indicated significant nesting, ground surveys were carried out to confirm species identifications and to gather information about exploitation and predation. Age classes were determined by size, weight and, when possible, necropsy. The aerial survey techniques employed in this study are described in detail by Pritchard et al. (1983).

Surveys of foraging grounds and developmental habitats

The distribution of turtle foraging habitats such as the grass flats of Mussulo Bay and rocky outcroppings in offshore waters was determined by aerial reconnaissance supplemented by ground surveys. Three trips were made by boat to Mussulo Bay.

RESULTS

Interviews

Approximately 50 Angolans, ranging from biologists to fishermen, were interviewed and all agreed that sea turtles occurred regularly in Angola, although there was some confusion as to the species represented. Three types of turtles were generally recognized. One was the 'big turtle' (Dermochelys coriacea). Local names for it were 'tartaruga gigante', 'ya dikota', and 'kitabanga'. The second was the 'little turtle' (Chelonia mydas or Lepidochelys olivacea). The two species were regularly confused, and only distinguished by people who lived on nesting beaches or near foraging habitats. Where the green and ridley turtles were distinguished, local names were, respectively, 'yofele' and 'mbaxi'. The third kind of turtle generally recognized was the freshwater Nile softshell turtle Trionyx triunguis. Other names that we heard applied to sea turtles, but not firmly associated with a particular species, were: Galenea, Xito, Mundo, Gorduna, Kicove, Luanha, Nhamu, and N'Pese. No-one interviewed was able or willing to make estimates of the relative abundance of each species in Angola, but people on several nesting beaches and bay shores said that turtles were numerous in their respective areas. Nesting beaches for all three species of sea turtle found in Angola were reported to have their greatest nesting activity during November, December and January, although some people reported nesting

22 T. Carr, N. Carr

as early as September and October. Others named February and March as active months. One woman stated that residents of Praia da Palmerinhas had caught a leatherback nesting in August, and there was a report of sea turtles nesting in Benguela during the month of June.

An observation that was made several times by people interviewed was that the beginning of nesting closely coincides with the commencement of the rainy season. Most interviewees at Mussulo Bay stated that green turtles live in the bay year-round, and many coastal residents reported catching juvenile, subadult, and adult greens, ridleys, and leatherbacks in their nets or finding them dead on the beach throughout the year. In the coastal waters adjacent to nesting beaches, the turtles observed offshore in the period April through September were few, as compared with reports of turtles at sea during the nesting season. It was difficult to assess the relative abundance of turtles of different size classes in Angolan waters, because many people interviewed thought that different sizes were indicative of different species. We concluded, however, that juvenile, subadult, and mature green turtles reside in or visit Mussulo Bay.

Nesting surveys

Approximately 430 km, or 54%, of the total coastline surveyed was classified as suitable for nesting by sea turtles. All of the (turtle) beaches in the Province of Cabinda were narrow, with light to moderate wave action under normal conditions. From the mouth of the Congo River south to Quicombo the shore varied from narrow, low-energy strand (c. 39%) to broad, high- energy beaches with heavy wave action and high sand berm (c. 61%). A total of 559 nests or nesting attempts were recorded from the northern border of Cabinda to Quicombo during both the 1983 and 1985 visits to Angola. In 1983, a total of 73 nests or nesting attempts were recorded between the Province of Cabinda to the north, and Quicombo to the south (Figs i-2). Of these, 41 were fresh or no more than a week old, and 32 were old leatherback nests, probably from the last nesting season. Six of the 41 identifiable crawls were made by olive ridleys, and eleven by green turtles. The 24 unidentifiable nests were believed to have been made by green turtles, and, in a few cases, by olive ridleys. Although according to local residents the nesting season was just beginning, evidence of significant nesting activity was seen. In 1985, a total of 486 nests or nesting attempts were recorded from Luanda to the north, and Rio Longa to the south (Fig. 3). Of these, 100 nests were made by olive ridleys and 66 by leatherbacks. Although the other 320 nests were not confirmed by ground truthing, they were recorded by the authors as being those of olive ridleys. The only exceptions were several crawls, which were believed to be those of green turtles.


CABINDA-1983 R E P U B L I C OF A N G O L A

o& Unidentified Turtle Nests

"m L_epidochely~ olivacea Nests

"O Chelonia rny£1JhS Nests

"Q Dermochely~ coriacea Nests =OR NEST ATTEMPTS

SURVEY- OCTOBER 26

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Turtle nests or nest attempts encountered during the 1983 Cabinda survey,

Surveys of forage grounds and developmental habitats

Most of the juvenile or subadult turtles seen during the survey were in or near one of the many small bays along the coast. A close inspection of Mussulo Bay was made by aircraft, as well as by boat. Mussulo Bay, one of the largest in Angola (152km2), is mostly well-protected from wind and wave action. Its relatively clear water supports a wide variety of marine flora and fauna. Corals, algae, and seagrass Diplanthera fiats were found throughout the bay. All of the 12 Mussulo inhabitants interviewed agreed that turtles are present in the bay year-round, although there were seasonal variations. During the boat survey of Mussulo Bay, 23 whole or partial sea turtles were observed. Eleven of these were adult green turtles, eight were juvenile and subadult greens, two were olive ridleys and two were not identified. The Nile softshell turtle was also encountered in Mussulo Bay, as well as in other similar habitats visited during the survey. It was frequently considered by the locals to be a kind of sea turtle. The softshell is said to be present in the bay year-round and is caught in gill nets and trotlines set by the natives to catch ground fish. Inspection of two shops in Luanda which sold sea turtle parts and jewelry indicated that the Mussulo area is of considerable importance as habitat for all size classes of sea turtles.

Subadult and adult leatherbacks were encountered in the relatively clear water adjacent to the broad, high-energy beaches where evidence of nesting

24 T. Carr, N. Carr

ANGOLA- 1983 LUANDA-- RIO ZAIRE

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Quicombo.


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A NGOLA-1985 LUAN DA - R IO LONGA

m--Lepidochelys ol ivaces Nests

O'Oermochelys coriacea Nests

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Turtle nests or nest attempts encountered during the 1985 survey from Luanda to Rio Longa.

by this species was found. Some animals were seen feeding on jellyfish, which were abundant throughout the study area.

Immature, subadult and mature green turtles were encountered throughout the areas surveyed. Most of the young greens were seen swimming at the surface or had been captured in estuaries or bays.

Adult olive ridleys were encountered throughout the study area. This

40.

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( E x c l u d i n g Uncon f i rmed da ta )

1201 N tO0 - - . . .

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LUANDA TO RIO LONGA

Comparison of numbers of turtles at sea and turtle nests by species, per area, for 1983 and 1985.

26 T. Carr, N. Carr

species was the predominant sea turtle in the Bay of Bengo, approximately 21 km north of Luanda. Evidence from surveys suggests that it is also common in the Bay of Cabinda.

During the aerial surveys, a total of 62 live sea turtles were sighted. Of these, 19 were identified as green turtles, nine as olive ridleys, and seven as leatherbacks (Fig. 4). Twenty-seven turtles could not be identified as to species because of adverse sighting conditions. However, all of the unidentified sightings were believed to be either immature green turtles or olive ridleys. No loggerheads or hawksbills were seen anywhere in the study area.

EXPLOITATION

Dead adult olive ridleys were encountered on the beach at Praia de San Tiago. Fishermen we interviewed reported catching turtles incidentally in their fish nets and regularly eating them. Those who found turtles nesting on the beach said they ate both the turtle .and the eggs. One fisherman reported capturing turtles with a harpoon. Some people described searching for nests with pointed sticks, and said they waited in the evening for the turtles to come to the beach so they could turn them over, to be slaughtered and butchered in the morning. Most frequently, however, the sea turtles that were eaten were caught incidentally in small-mesh gill-nets or beach seines, or were taken offthe nesting beach. Most people did not differentiate among species with regard to quality of the meat; they relished them all. However, two fishermen who catch primarily green turtles did consider that meat to be superior.

Although most people interviewed eat any turtle meat or eggs they can get, they were willing to sell both meat and shell. Prices were surprisingly high. In one locality, we found that the price of an olive ridley flipper was 1000 Kwanzas, or US$33, and that the entire turtle sold for 6000 Kwanzas, or US$182. This astonishingly high price for an adult ridley was low when compared with the 3000 Kwanzas asked for a 3-5 kg fish. Turtle shells could be bought off the beach for as low as 3000 Kwanzas in outlying areas, but sold for up to 10000 Kwanzas near Luanda. Sea turtle eggs were not found for sale anywhere during the study. In Luanda carved olive ridley and green turtle shells could be purchased for 25 000 to 40 000 Kwanzas.

During both surveys, a total of 124 whole or partial carcasses of sea turtles were encountered, including the remains of 36 green turtles, 38 olive ridleys and eight leatherbacks. Although most of these remains were found in the field, some were examined in curio shops, residences and government institutions, Seven loggerhead shells were observed--two in curio shops, and five that had been confiscated in 1982 by the Angolan government. Six of the


shells had been carved, and all appeared to be quite old. It was suggested by some curio shop owners that these shells might have been imported from Mozambique, as had other items being sold in their shops. Items made of hawksbill shell such as necklaces, earrings, and rings were found for sale in curio shops in Luanda. Government officials and shop owners maintained that all the tortoise shell articles sold in shops were from the island of Sao Tome. No other carcasses, remains, reports, or other evidence of either hawksbills or loggerheads were found during our surveys.

Our data suggested that juvenile, subadult and mature green turtles, subadult and mature leatherbacks, and mature olive ridleys were taken throughout the non-nesting season. Most of the sea turtles captured during those months, when nesting was not taking place, were caught incidentally in gill-nets set for fish in inshore waters. Very little evidence of dedicated turtling, i.e. harpooning or use of special turtle nets, was found along Angola's coast at any time throughout the year.

Predation by wild or feral animals

Aerial and ground surveys of nesting beaches revealed that predation on turtle nests by domestic and wild animals was widespread. Evidence of nest excavation by domestic dogs and pigs, and of predation by wild animals such as hyena, jackal, mongoose, and viverids (civet and genet), was found throughout the study area. In 1983, while surveying a 3-km stretch of nesting beach approximately 5 km north of Rio do Cuanza bar, we discovered that 35 of 37 nests encountered had been raided, mostly by wild animals. According to local coastal inhabitants, other occasional nest predators included lions, leopards, monitor lizards and wild pigs.

Protective legislation and enforcement

Sea turtles were first placed on the list of protected animals under the hunting laws of the Angolan government in 1972. In 1978 an addendum (Despacho No. 64/78) listed the most endangered animal species in Angola, and the sea turtle species are (all) on that list. Under this legislation, a relatively heavy fine of 10000 Kwanzas (US$330) was imposed for violations. Enforcement responsibility rests with the Capitania and the Ministry of Agriculture. Recent attempts to increase the fine have not been successful. In 1982 game wardens of the Ministry of Agriculture, Direccao Nacional de Conservacao da Natureza, carried out raids on the curio shops in Luanda and confiscated contraband sea turtle shells. At the same time, laws strictly forbidding export of sea turtle parts were implemented.

28 T. Cart, N. Carr

Although government authorities have plans for the enforcement of laws protecting sea turtles within Angola, domestic exploitation of turtle meat, eggs and shells by coastal inhabitants is extensive. During the nesting season, all species of sea turtles and their eggs are taken.

Continued government efforts to record, investigate, manage, and protect the sea turtles include research, regulation and enforcement of laws and a vigorous public education program. To be effective, an education campaign should not be restricted to the people who live near and exploit the sea turtles, but should spread awareness of the problems throughout the country. The highest priority should be given to organizing a diverse program of public relations operations, including posters, lectures, movie films and videotapes depicting the present threat to a depleted wildlife resource that is being overexploited, but is susceptible to rehabilitation as a natural asset.

To consolidate the benefits to be expected from the public relations program, there is a need for long-term research including one or more seasonal tagging programs. These should be resumed each season over a period of five years or more. The resulting tag recoveries at the nesting beach and at a distance from it will provide information on population sizes and changes, on internesting and remigration intervals, and on the post-season movements and migratory routes of the nesting colonies.

A C K N O W L E D G E M ENTS

The work in Angola was made possible by the following institutions and organizations: Wildlife Conservation International of the New York Zoological Society; Ministerio da Agricultura (DNACO), People's Republic of Angola; UNESCO Division of Ecological Sciences (MAB); Departmento de Biologia, Universidade de Angola; Sanangol Angola; Texaco Corpor- ation, and Cabinda Gulf. We are deeply grateful for the assistance and friendly participation of all the above institutions and organizations, to Dr Archie F. Carr of the Caribbean Conservation Corporation, to Dr Anne Meylan and Dr Gail Carr for comments. The illustrations were prepared by Janet Zugar.

REFERENCES

Brongersma, L. D. (1961). Notes upon some sea turtles. Zool. Verb. Leiden, 51, 1-46. Brongersma, L. D. (1982). Marine turtles of the Eastern Atlantic Ocean. In Biology

and Conservation of Sea Turtles, ed. K. Bjorndal. Smithsonian Institution Press, Washington, DC, pp. 407-16.


Carr, A., Meylan, A., Mortimer, J., Bjorndal, K. & Carr, T. (1982). Surveys of sea turtle populations and habitats in the western Atlantic. NOAA Tech. Mem. NMFS-SEFC-91.

du Bocage, J. V. (1866). Lista dos reptis das possessoes portuguezas d'Africa occidental que existen no Museu de Lisboa. J. Sci. Math. Phys. Nat., Acad. Sci. Lisboa, I, 1-48.

du Bocage, J. V. (1895). Herpetologie d'Angola et du Congo. Lisbon, Imprimerie Nationale.

Fretey, J. & Girardin, N. (1988). La nidification de la tortue luth, Dermochelys coriacea (Vandelli, 1761) (Chelonii, Dermochelyidae) sur les c6tes du Gabon. J. Afr. Zool., 102, 125 32.

Hughes, G. R. (1982). Conservation of sea turtles in the southern Africa region. In Biology and Conservation of Sea Turtles, ed. K. Bjorndai. Smithsonian Institution Press, Washington DC, pp. 397-404.

Hughes, G. R., Huntley, B. & Wearne, D. (1973). Sea turtles in Angola. Biol. Conserv., 5, 58-9.

H untley, B. J. (1978). Ecosystem conservation in southern Africa. In Biogeography and Ecology of Southern Africa, Monographiae Biologicae, 31. ed. M. J. A. Werger & A. C. van Bruggen. W, Junk, The Hague, pp. 1333-84.

Monard, A. (1937). Contribution fi l'herpetologie d'Angola. Arq. Mus. Bocage, 8, 19-153.

Pritchard, P., Bacon, P., Berry, F., Carr, A., Fletemeyer, J., Gallagher, R., Hopkins, S., Lankford, R., Marquez, M. R., Ogren, L., Pringle, W., Jr, Reichart, H. & Witham, R. (1983). Manual of Sea Turtle Research and Conservation Techniques, 2nd edn, ed. K. A. Bjorndal & G. H. Balazs. Center for Environmental Education, Washington, DC.

Documents

Surveys of the sea turtles of Angola