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

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

Soweto Munto Nkulo Pangaio Farol Comissete Vamizi Island Study site 10,5km of nesting beaches Main nesting beaches: Comissete e Farol GroupSections Comissete1-41 Soweto+Farol42-73 Pangaio+Munto Nkulo74-105

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 *(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,, Karavas et al., 2005, Mortimer, 1990). Multiple environmental factors (Mazaris et al., 2006)

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

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

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

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

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

Results and discussion Factors that influenced nest site selection Year Beach Width (B) % Dune (B) Rock Cover (B) Proximity to promontories (B) Tree + Bush Height (B) % Herbs (B) Correctly classified points R²R² 20031,0600,020-1, ,3%0, , ,5%0, , , ,3%0, , ,3%0, ,7330,025-1,014--0,212-82,9%0, , ,1%0, ,4500,043-0, ,7%0, , ,196-76,2%0,378

Results and discussion Change in the beach preference pattern Individual preferences Positive Indian Ocean Dipole Events Individual preferences Same female doesn’t nest every year (3-4 years) Females might be influenced by different factors Change in the sections that are chosen more or less often Indian Ocean Dipole (IOD) Impossible to test without tagging each individual We would expect the pattern to be observed in other years Change in consecutive years contradicts the fact that females rarily nest in consecutive years Climate indexes used to explain population dynamics (Limpus & Nicholls, 2000; Chaloupka, 2001; Saba et al., 2007 in Chaloupka et al., 2007) Sea turtles are affected by SST and oceanic currents (Poloczanska et al., 2009) Changes in SST + South Equatorial Current  turtle movements  changes in the nest site selection pattern 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 Dificult to prove hypothesis

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

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

Obrigada! Asante! Thank you!