Skip to main content

Advertisement

SpringerLink
Log in

Bioko: critically important nesting habitat for sea turtles of West Africa

  • Original Paper
  • Published:
Biodiversity and Conservation Aims and scope Submit manuscript

Abstract

We evaluate the conservation status and threats faced by sea turtle nesting populations at Bioko Island, Equatorial Guinea (Central Africa). Beaches were monitored to obtain a detailed sea turtle nest census and, where possible, tagging of adult females was undertaken. Four sea turtle species were found nesting in the area: the green turtle (Chelonia mydas), the leatherback (Dermochelys coriacea), the olive ridley (Lepidochelys olivacea) and the hawksbill (Eretmochelys imbricata); with the former two species nesting in regionally important numbers. Nesting activity was concentrated between November and February, with a peak in December–January. Tagging and recapture of green turtles in two consecutive seasons suggested an estimated 560 (interquartile range: 420–1,681) and 414 (interquartile range: 190–1,255) nesting females in the area, respectively. Estimated numbers of nesting leatherbacks ranged from 123 to 215 and 243 to 293 in the first and second season, respectively. The other two species were less abundant (olive ridley: 19–29 and 28–43; hawksbill: 4–10 and 2 turtles). Data were compared with more recent surveys in the area and contextualised with information on human related threats. Despite the size of nesting stocks, ongoing permitted and illegal take of adult turtles at the nesting site constitutes a serious threat for these breeding aggregations. Additionally, tag returns from throughout the Gulf of Guinea suggest that the level of take in regional fisheries may also be a major threat.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5

Similar content being viewed by others

References

  • Alvarado J, Murphy TM (1999) Nesting periodicity and internesting behaviour. In: Eckert KL, Bjorndal KA, Abreu-Grobois FA, Donnelly M (eds) Research and management techniques for the conservation of sea turtles. IUCN/SSC Marine Turtle Specialist Group Publication No. 4, pp 115–118

  • Alvarado-Diaz J, Arias-Coyotl E, Delgado-Trejo C (2003) Clutch frequency of the Michoacan green seaturtle. J Herpetol 37:183–185

    Article  Google Scholar 

  • Anonymous (2000) Informe sobre algunos aspectos de la biología reproductiva de las tortugas marinas y su explotación en la isla de Bioko. Unpublished report. Proyecto de Conservación y Ecodesarrollo en el Sur de la isla de Bioko (Guinea Ecuatorial), Eoco y zona oriental. Asociación Amigos de Doñana, Malabo, Equatorial Guinea, p 15

  • Billes A, Fretey J, Mourndembe JB (2003) Monitoring of leatherback turtles in Gabon. In: Seminoff J (comp) Proceedings of the 22nd annual symposium of sea turtle biology and conservation. NOAA-TM-NMFS-SEFSC-503, Miami, USA, pp 131–132

  • Bjorndal KA, Carr A, Meylan AB, Mortimer JA (1985) Reproductive biology of the hawksbill turtle Eretmochelys imbricata at Tortuguero, Costa Rica, with notes on the ecology of the species in the Caribbean. Biol Conserv 34:353–368

    Article  Google Scholar 

  • Bjorndal KA, Bolten AB, Lagueux CJ, Chaves A (1996) Probability of tag loss in green turtles nesting at Tortuguero, Costa Rica. J Herpetol 30(4):567–571

    Article  Google Scholar 

  • Bolten AB (1999) Techniques for measuring sea turtles. In: Eckert KL, Bjorndal KA, Abreu-Grobois FA, Donnelly M (eds) Research and management techniques for the conservation of sea turtles. IUCN/SSC Marine Turtle Specialist Group Publication No. 4, pp 110–114

  • Broderick AC, Godley BJ, Hays GC (2001) Trophic status drives inter-annual variability in nesting numbers of marine turtles. Proc R Soc Lond B 268:1481–1487

    Article  CAS  Google Scholar 

  • Broderick AC, Glen F, Godley BJ, Hays GC (2002) Estimating the number of green and loggerhead turtles nesting annually in the Mediterranean. Oryx 36(3):227–235

    Article  Google Scholar 

  • Broderick AC, Glen F, Godley BJ, Hays GC (2003) Variation in reproductive output of marine turtles. J Exp Mar Biol Ecol 4097:1–15

    Google Scholar 

  • Brongersma LD (1982) Marine turtles of the eastern Atlantic Ocean. In: Bjorndal KA (ed) Biology and conservation of sea turtles. Smithsonian Institute Press, Washington, DC, pp 407–416

    Google Scholar 

  • Butynski TM (1996) Marine turtles on Bioko Island, Equatorial Guinea. Oryx 30(2):143–149

    Article  Google Scholar 

  • Butynski TM, Koster SH (1989) Marine turtles on Bioko Island (Fernando Poo), Equatorial Guinea: a call for research and conservation. WWF Unpublished Report, Washington, DC

  • Butynski TM, Koster SH (1994) Distribution and conservation status of primates in Bioko Island, Equatorial Guinea. Biodivers Conserv 3:893–909

    Article  Google Scholar 

  • Carr A, Carr MH (1970) Modulated reproductive periodicity in Chelonia. Ecology 51(2):335–337

    Article  Google Scholar 

  • Carranza A, Domingo A, Estrades A (2006) Pelagic longlines: a threat to sea turtles in the Equatorial Eastern Atlantic. Biol Conserv 131:52–57

    Article  Google Scholar 

  • Castroviejo J, Juste J, Pérez Del Val J, Castelo R, Gil R (1994) Diversity and status of sea turtle species in the Gulf of Guinea islands. Biodivers Conserv 3:828–836

    Article  Google Scholar 

  • Catry P, Barbosa C, Indjai B, Almeida A, Godley BJ, Vié JC (2002) First census of the green turtle at Poilão, Bijagós Archipelago, Guinea-Bissau: the most important nesting colony on the Atlantic coast of Africa. Oryx 36(4):400–403

    Article  Google Scholar 

  • Chacón-Chaverri D (1999) Anidación de la tortuga Dermochelys coriacea (Testudines: Dermochelyidae) en la playa Gandoca, Costa Rica (1990–1997). Rev Biol Trop 47(1–2):225–236

    Google Scholar 

  • Dutton DL, Dutton PH, Chaloupka M, Boulon RH (2005) Increase of a Caribbean leatherback turtle Dermochelys coriacea nesting population linked to long-term nest protection. Biol Conserv 126:186–194

    Article  Google Scholar 

  • Eckert SA (2006) High-use oceanic areas for Atlantic leatherback sea turtles (Dermochelys coriacea) as identified using satellite telemetered location and dive information. Mar Biol 149:1257–1267

    Article  Google Scholar 

  • Formia A (2002) Population and genetic structure of the green turtle (Chelonia mydas) in West and Central Africa; implications for management and conservation. PhD dissertation, Cardiff University, UK

  • Formia A, Tomás J, Castelo R (2000) Nidification des tortues marines au sud de Bioko. Canopée 18:i–iv

    Google Scholar 

  • Formia A, Tiwari M, Fretey J, Billes A (2003) Sea turtle conservation along the Atlantic coast of Africa. Mar Turt Newsl 100:33–37

    Google Scholar 

  • Formia A, Godley BJ, Dontaine JF, Bruford MW (2006) Mitochondrial DNA diversity and phylogeography in African green turtles (Chelonia mydas). Conserv Genet 7:353–369

    Article  CAS  Google Scholar 

  • Formia A, Broderick AC, Glen F, Godley BJ, Hays GC, Bruford MW (2007) Genetic composition of the Ascension Island green turtle rookery based on mitochondrial DNA; implications for sampling and diversity. Endanger Species Res 3:145–158

    Article  Google Scholar 

  • Fretey J (2001) Biogeography and conservation of marine turtles of the Atlantic coast of Africa. CMS Technical Series Publication No. 6. UNEP/CMS Secrertariat, Bonn, Germany

  • Fretey J, Billes A, Tiwari M (2007) Leatherback, Dermochelys coriacea, nesting along the Atlantic coast of Africa. Chelonian Conserv Biol 6:126–129

    Article  Google Scholar 

  • Girondot M, Godfrey MH, Ponge L, Rivalan P (2007) Modelling approaches to quantify leatherback nesting tends in French Guiana and Suriname. Chelonian Conserv Biol 6:37–46

    Article  Google Scholar 

  • Godley BJ, Blumenthal JM, Broderick AC, Coyne MS, Godfrey MH, Hawkes LA, Witt MJ (2008) Satellite tracking of sea turtles: where have we been and where do we go next? Endanger Species Res 4:3–22

    Article  Google Scholar 

  • Hirth HF (1997) Synopsis of biological data on the green turtle Chelonia mydas (Linnaeus, 1758). Fish and Wildlife Service, U.S. Department of the Interior, Biological Report 97(1)

  • Jackson AL, Broderick AC, Fuller WJ, Glen F, Ruxton GD, Godley BJ (2008) Sampling design and its effect on population monitoring: how much monitoring do turtles really need? Biol Conserv 141:2932–2941

    Article  Google Scholar 

  • Kalb HJ (1999) Behaviour and physiology of solitary and arribada nesting olive ridley sea turtles during the interesting period. PhD dissertation, Texas A&M University, College Station, TX, USA

  • Le Gall J-Y, Bosc P, Chateau D, Taquet M (1986) Estimation du nombre de tortues vertes femelles adultes Chelonia mydas par saison de ponte à Tromelin et Europa (Océan Indien) (1973–1985). Oceanogr Trop 21(1):3–22

    Google Scholar 

  • Limpus CJ (1992) Estimation of tag loss in marine turtle research. Wildl Res 19:459–469

    Google Scholar 

  • Limpus CJ, Carter D, Hamann M (2001) The green turtle, Chelonia mydas, in Queensland, Australia: the Bramble Cay rookery in the 1979–1980 breeding season. Chelonian Conserv Biol 4:34–46

    Google Scholar 

  • Limpus CJ, Miller J, Parmenter C, Limpus D (2003) The green turtle, Chelonia mydas, population of Raine Island and the northern Great Barrier Reef 1843–2001. Mem Qld Mus 49:349–440

    Google Scholar 

  • Mba Mba J, Nguema J, García JE (1998) Estudio y Conservación de las tortugas marinas en el litoral de la región continental de Guinea Ecuatorial (1ª fase). Technical Report No11-SUC. Proyecto Conservación y Utilización Racional de los Ecosistemas Forestales de Guinea Ecuatorial (C.U.R.E.F.). Bata, Guinea Ecuatorial

    Google Scholar 

  • McGowan A, Broderick AC, Frett G, Gore S, Hastings M, Pickering A, Wheatly D, White J, Witt MJ, Godley BJ (2008) Down but not out: marine turtles of the British Virgin Islands. Anim Conserv 11:92–103

    Article  Google Scholar 

  • Mortimer JA, Bresson R (1999) Temporal distribution and periodicity in hawksbill turtles (Eretmochelys imbricata) nesting at Cousin Island, Republic of Seychelles, 1971–1997. Chelonian Conserv Biol 3(2):318–325

    Google Scholar 

  • Patiño-Martínez J, Marco A, Quinones L, Godley BJ (2008) Globally significant nesting of the leatherback turtle (Dermochelys coriacea) on the Caribbean coast of Columbia and Panama. Biol Conserv 141:1982–1988

    Article  Google Scholar 

  • Pérez del Val J (1996) In: Pastor V (ed) Las aves de Bioko, Guinea Ecuatorial. EDILESA, Leon

  • Pilcher NJ (2000) The green turtle, Chelonia mydas, in the Saudi Arabian Gulf. Chelonian Conserv Biol 3(4):730–734

    Google Scholar 

  • Rader H, Ela Mba MA, Morra W, Hearn G (2006) Marine turtles on the southern coast of Bioko Island (Gulf of Guinea, Africa), 2001–2005. Mar Turt Newsl 111:8–10

    Google Scholar 

  • Reina RD, Mayor PA, Spotila JR, Piedra R, Paladino FV (2002) Nesting ecology of the leatherback turtle, Dermochelys coriacea, at Parque Nacional Marino Las Baulas, Costa Rica: 1988–1989 to 1999–2000. Copeia 2002(3):653–664

  • Reina RD, Spotila JR, Paladino FV (2007) Why older ladies are better. In: Mast RB, Hutchinson BJ, Hutchinson AH (comps) Proceedings of the twenty-fourth annual symposium on sea turtle biology and conservation. NOAA Technical Memorandum NMFS-SEFSC-567, pp 32–33

  • Reina RD, Spotila JR, Paladino FV, Dunham AE (2008) Changed reproductive schedule of eastern pacific leatherback turtles Dermochelys coriacea following the 1997–1998 El Nino to La Nina transition. Endanger Species Res. doi:10.3354/esr00098

  • Richardson JI, Bell R, Richardson TH (1999) Population ecology and demographic implications drawn from an 11-year study of nesting hawksbill turtles, Eretmochelys imbricata, at Jumby Bay, Long Island, Antigua, West Indies. Chelonian Conserv Biol 3(2):44–250

    Google Scholar 

  • Sounguet GP, Mbina C, Formia A (2004) Sea turtle research and conservation in Gabon by Aventures Sans Frontières, an organisational profile. Mar Turt Newsl 105:19–21

    Google Scholar 

  • Steyermark AC, Williams K, Spotila J, Paladino FV, Rostal DC, Morreale S, Koberg MT, Arauz R (1996) Nesting leatherback turtles at Las Baulas National Park, Costa Rica. Chelonian Conserv Biol 2(2):173–183

    Google Scholar 

  • Tomás J, Castroviejo J, Raga JA (1999) Sea turtles in the south of Bioko Island (Equatorial Guinea). Mar Turt Newsl 84:4–6

    Google Scholar 

  • Tomás J, Formia A, Castroviejo J, Raga JA (2001a) Post-nesting movements of the green turtle, Chelonia mydas, nesting in the south of Bioko Island, Equatorial Guinea, West Africa. Mar Turt Newsl 94:3–6

    Google Scholar 

  • Tomás J, Fretey J, Raga JA, Castroviejo J (2001b) Tortues marines de la façade atlantique de l’Afrique. Genre Lepidochelys. 1. Quelques données concernant la présence de L. olivacea (Eschscholtz, 1829) dans l’île de Bioko (Guinée Équatoriale). Bull Soc Herpetol France 98:31–42

    Google Scholar 

  • Troëng S, Chacón D, Dick B (2004) Possible decline in leatherback turtle Dermochelys coriacea nesting along the coast of Caribbean Costa Rica. Oryx 38:395–403

    Article  Google Scholar 

  • Tucker AD (2010) Nest site fidelity and clutch frequency of loggerhead turtles are better elucidated by satellite telemetry than by nocturnal tagging efforts: implications for stock estimation. J Exp Mar Biol Ecol 383:48–55

    Article  Google Scholar 

  • Witt MJ, Broderick AC, Coyne MS, Formia A, Ngouessono S, Parnell RJ, Sounget G-P, Godley BJ (2008) Satellite tracking highlights difficulties in the design of effective protected areas for leatherback turtles during the internesting period. Oryx 42:296–300

    Article  Google Scholar 

  • Witt MJ, Baert B, Broderick AC, Formia A, Fretey J, Gibudi A, Moussounda C, Mounguengui GAM, Ngouessono S, Parnell RJ, Roumet D, Sounguet G-P, Verhage B, Zogo A, Godley BJ (2009) Aerial surveying of the world’s largest leatherback turtle rookery: a more effective methodology for large-scale monitoring. Biol Conserv 142(8):1719–1727

    Article  Google Scholar 

Download references

Acknowledgements

The authors express a sincere gratitude to the local villagers of Ureca (South Bioko) who actively participated in the surveys and assisted J. Tomás during fieldwork. The present study was undertaken within the framework of a conservation project carried out by the Spanish NGO Asociación Amigos de Doñana, and we particularly thank the valuable help of Ramón Castelo, Juan Enrique García and the staff that worked in the project between 1995 and 1998. Drs. J. Aznar and J.A. Balbuena provided valuable comments and assistance during the data analyses. J. T. is supported by a Marie Curie Postdoctoral Fellowship, and B. J. G. receives support from the Darwin Initiative, European Social Fund Project and the Natural Environment Research Council. The manuscript was improved by the comments of the Editor and two anonymous referees.

Author information

Authors and Affiliations

  1. Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Penryn, TR10 9EZ, UK

    Jesús Tomás & Brendan J. Godley

  2. Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, Aptdo. 22085, 46071, Valencia, Spain

    Jesús Tomás & Juan A. Raga

  3. Asociación Amigos de Doñana, C/Panamá 6, 41012, Sevilla, Spain

    Javier Castroviejo

Authors
  1. Jesús Tomás
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Brendan J. Godley
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Javier Castroviejo
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Juan A. Raga
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Jesús Tomás.

Appendix

Appendix

Spatial distribution of nesting effort

The relative distribution of estimated nesting effort, both nesting activities, i.e. emergences of nesting females to nest either false or successful (a), and clutches deposited (b) for three turtle species (green turtle C. mydas, leatherback D. coriacea and olive ridley L. olivacea) by beach sector and by year, including: total number of activities, density and relative proportion for that species and season. Hawksbill turtles E. imbricata only included in Table 2 due to very low numbers. Total distance of each zone is shown in brackets under the indicative letter. The distribution of activities show the beach preferences exhibited by each species and the increase of leatherback nesting in beach A in 1997/1998 (see Tables 1 and 2).

Table 1 Number of nesting activities per study beach in each of the two study seasons
Full size table
Table 2 Number of clutches per study beach in each of the two study seasons
Full size table

Rights and permissions

Reprints and permissions

About this article

Cite this article

Tomás, J., Godley, B.J., Castroviejo, J. et al. Bioko: critically important nesting habitat for sea turtles of West Africa. Biodivers Conserv 19, 2699–2714 (2010). https://doi.org/10.1007/s10531-010-9868-z

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s10531-010-9868-z

Keywords

Search

Navigation