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Supervisors: Prof. Dr. Rui Rebelo Prof. Dr. Almeida Guissamulo PowerPoint Presentation
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Supervisors: Prof. Dr. Rui Rebelo Prof. Dr. Almeida Guissamulo

Supervisors: Prof. Dr. Rui Rebelo Prof. Dr. Almeida Guissamulo

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Supervisors: Prof. Dr. Rui Rebelo Prof. Dr. Almeida Guissamulo

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  1. Conservation Science in Mozambique Joana Casimiro Trindade Factors that influenced nesting beach selection by green turtles (Cheloniamydas) in Vamizi, Mozambique, between 2003 and 2012 Supervisors: Prof. Dr. Rui Rebelo Prof. Dr. Almeida Guissamulo

  2. Overview Green turtle • Circumglobal species, feeding and nesting areas in tropical and subtropical waters • Big colonies: Costa Rica, Queensland, Ascencion Island and Poilão Island • Endangered (Red List IUCN) Consequences on the fitness of the hatchlings • Nest site selection

  3. Vamizi Island Study site Soweto Comissete Farol • 10,5km of nesting beaches • Main nesting beaches: Comissete e Farol Pangaio Munto Nkulo

  4. Nesting site selection Factors that influence nesting beach selection* • Elevation above the water mark • Slope • Vegetation cover • Beach width • Silhouette of objects behind the beach • Rock cover • Granulometry • Multiple environmental factors (Mazaris et al., 2006) *(Burger & Montevecchi, 1975; Plummer, 1976; Cox and Marion, 1978; Ehrenfeld, 1979 in Wilson; 1998, Schwarzkopf & Brooks, 1987; Plummer et al., 1994 in Wilson, 1998, Mazaris et al., 2006, Botha, 2010, Mortimer, 1982, , Karavaset al., 2005, Mortimer, 1990).

  5. Goals • To understand the nesting process in Vamizi To evaluate if nesting was similar throughout the various nesting beach sections throughout the years To identify the factors that influenced nest site selection from 2003 t0 2012

  6. Methodology Data collection • Registration of nesting actions since 2002 • Profile, beach slope and granulometry • Proximity to promontaries No nest 0 1 or more nests  1 • Section

  7. Methodology • Beach characterization • Step height • Beach width • Signs of erosion • % dune • Height and % of vegetation • Rock cover

  8. Statistic analysis • Are there differences in the number of nests per section? nests per group? nests per section in each group? • Which variables are related to the presence of nests?

  9. Results and discussion Distribution of nests throughout the years Nests/section 2006 Nests/section 2005 Nests/section 2006 • ≠s number of nests/section abandonment sections 1 to 58 in 2006 and 2007 Nests/section 2008 more frequent use of sections 57 to 105 in 2007 and 2008 • ≠s number of nests/group • ≠s number of nests/section/group Comissete

  10. Results and discussion Factors that influenced nest site selection

  11. Results and discussion Individual preferences Positive Indian Ocean Dipole Events • Individual preferences • Indian Ocean Dipole (IOD) • Change in the beach preference pattern Climate indexes used to explain population dynamics (Limpus & Nicholls, 2000; Chaloupka, 2001; Saba et al., 2007 in Chaloupka et al., 2007) Same female doesn’t nest every year (3-4 years) Impossible to test without tagging each individual We would expect the pattern to be observed in other years Capacity to correct drifts in their routes (Benhamou et al., 2011) + there are no direct evidences that the IOD may lead to a change in nest site selection Change in the sections that are chosen more or less often Sea turtles are affected by SST and oceanic currents (Poloczanska et al., 2009) Females might be influenced by different factors Change in consecutive years contradicts the fact that females rarily nest in consecutive years Changes in SST + South Equatorial Current  turtle movements  changes in the nest site selection pattern Dificult to prove hypothesis

  12. Implications for conservation Biological and environmental variables linked to higher nest densities and hatching success (Kolbe & Janzen, 2002) Spacial analysis of the nesting pattern Identify priority nesting beaches  higher level of protection

  13. Implications for conservation • Farol EROSION!! Appearance of steps access to vegetation zone Soweto Comissete nest construction in erosion/flooding prone areas Farol main focus in terms of protection best conditions: beach width + number of nests Pangaio Munto Nkulo

  14. Obrigada! Asante! Thank you!