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Marine Turtle Newsletter 146:9-10, © 2015
Natural Death of a Hawksbill Turtle Due to Feeding Behavior
M.C. Proietti1, V.C. Marques2, M.L. Marques2, F.P.M. Repinaldo2, A.L.F. Lacerda1 & J. Barreto3,4
1Instituto de Oceanografia, Universidade Federal do Rio Grande, Brazil (E-mail: mairaproietti@gmail.com, analuzialacerda@gmail.com);
2Instituto Chico Mendes de Conservação da Biodiversidade - Parque Nacional Marinho
dos Abrolhos, Brazil (E-mail: vitorcmarques@hotmail.com, marinaleitemar@gmail.com, fernando.repinaldo@icmbio.gov.br);
3Fundação Centro Brasileiro de Proteção e Pesquisa das Tartarugas Marinhas, Fundação Pró-TAMAR, Brazil;
4Laboratório de Ictiologia, Departamento de Oceanografia, Universidade Federal do Espírito Santo, Brazil (E-mail: joe@tamar.org)
The Abrolhos Archipelago (17.93°S, 38.94°W), located within the Abrolhos National Marine Park, is an important feeding area for immature hawksbill turtles Eretmochelys imbricata (Proietti et al. 2012). This species is generally carnivorous and has been reported to feed on a wide range of prey, with preference for ingesting sessile benthic organisms such as sponges and zoanthids (León & Bjorndal 2002; Proietti et al. 2012; Stampar et al. 2007). At the archipelago, hawksbill turtles are commonly seen at shallow reef areas, where they feed in a distinctive manner on the green sea mat Zoanthus sociatus (Fig. 1).
Figure 1. Live immature hawksbill turtles feeding on Zoanthus sociatus at the Abrolhos Archipelago.
On 18 March 2015, at 3:50 PM local time, while snorkeling at a protected bay (Mato Verde) of Santa Barbara Island, we observed an immature hawksbill turtle with its head wedged in a small crevice on the seabed, at approximately 2.5 m depth (Fig. 2a). After noting that the animal was unresponsive, we removed it from the seabed and determined that it was deceased. The turtle had initially been captured and tagged (left front flipper tag BR96926, right front flipper tag BR96927) on 3 March 2015, and was subsequently recaptured on 15 March at the same location. It measured 35.5 and 27.7 cm curved carapace length and curved carapace width, respectively, and weighed 6 kg. It had no apparent debilitation and its body showed no signs of degradation, which indicated that it had died just previously to us finding it.
Figure 2. Hawksbill turtle found deceased with head lodged in crevice (left); example of Zoanthus sociatus at Mato Verde Bay, Abrolhos Archipelago (right).
A visual inspection of the crevice revealed that the interior was lined with green sea mat (Fig. 2b). This is a common feature of this bay, and likely the reason why it is frequently visited by hawksbills during high tide. We believe that while eating this food item, the hawksbill got its head irremovably lodged in the crevice, and subsequently drowned. While anthropogenic threats are commonly reported for the Critically Endangered hawksbill turtle (Mortimer & Donnelly 2008), this is, to our knowledge, the first description of such an odd and natural cause of death.
Acknowledgements. We are grateful to Projeto Tamar-ICMBio and the Abrolhos National Marine Park for logistic and field support, and the Rufford Small Grants Foundation for funding. This is a contribution of the Research Group ‘Ecologia e Conservação da Megafauna Marinha - EcoMega.’
LEÓN, Y.M. & K.A. BJORNDAL. 2002. Selective feeding in the hawksbill turtle, an important predator in coral reef ecosystems. Marine Ecology Progress Series 245: 249-258.
MORTIMER, J.A. & M. DONNELLY. 2008. Hawksbill Turtle (Eretmochelys imbricata) Marine Turtle Specialist Group 2008 IUCN Red List status assessment. IUCN Red List of Threatened Species. www.iucnredlist.org
PROIETTI, M.C., J. REISSER & E.R. SECCHI. 2012. Immature hawksbill turtles feeding at Brazilian Islands. Marine Turtle Newsletter 135:4-6.
STAMPAR, S.N., P.F. DA SILVA & O.J. LUIZ. 2007. Predation on the zoanthid Palythoa caribaeorum (Anthozoa, Cnidaria) by a hawksbill turtle (Eretmochelys imbricata) in southeastern Brazil. Marine Turtle Newsletter 117:3-5.