156 J. Patino‐Martinez et al.
Nest site fidelity has been associated regularly with high- accuracy philopatric behaviour of sea turtles (Broderick et al., 2007; Lee et al., 2007) and this has also been reported for the rookery (Baltazar-Soares et al., 2020). However, random individual nesting patterns were ob-
served, with only 16% of the re-nesting events occurring within 1 km of the previous nests; re-nesting between differ- ent beaches was common. Some re-nesting events during the same season have been recorded between different Cabo Verdean islands that are separated by hundreds of kilometres (J. Patino-Martinez, pers. obs., 2021). We hypo- thesize that low beach fidelity could be a mechanism to increase the likelihood of placing some nests in environ- mentally suitable areas. This could increase the potential of loggerhead turtles to adapt to changing environments (Carreras et al., 2018). Beaches on Maio Island and else- where are often dynamic and their environment may not be predictable from one nesting event to the next (Kelle et al., 2007). Therefore, once the females are in the nesting area random beach selection could reduce the energetic cost of searching for a particular beach, the characteristics of which may not be stable and thus may not always be suitable for nesting. We found that nesting females have high-preference and
low-preference areas where they consistently re-nest or avoid re-nesting, respectively. Females exhibited high nest- ing zone consistency (64–71%) on the east coast of Maio Island even though this area had the lowest availability of nesting habitat. The high-preference areas could be a result of the clustering of conspecifics and hence higher chance of finding a mate (Shimada et al., 2021)or ofother as yet un- known factors. In two areas (north-north-west and south- south-east) there was low individual re-nesting zone consist- ency (10–25%). In these areas, and also in the rest of the island, the turtles who chose to re-nest in another area mainly did so on the east coast (the high-preference areas). The geographical areas of low preference coincide with a greater presence of people (poachers and rangers) on the nesting beaches (south-south-east) and more difficult access to the beach from the sea, with shallow waters (north-north-west). These and other parameters used as predictors of re-nesting preference should also be assessed in future studies (Mazaris et al., 2006). The available nesting sites on the island are generally
suitable for embryonic development but show varying nest- ing and hatching success rates. However, the pattern of re-nesting does not match the hatching success rates of nests in the study areas. Thus, the east-north-east zone had the greatest nesting success rate (65%) and hatching success rate (56%) in contrast with the east-south-east zone, which contains the beach with the lowest nesting success rate (22%) and hatching success rate (5.1%) of the whole island (Patino-Martinez et al., 2022a). Therefore, neither nest- ing success rate nor hatching success rate seems to be a
reliable indicator of consistency in the choice of re-nesting beaches. Some populations of loggerhead turtles prefer to nest in
areas with greater wind and wave exposure and therefore such nesting occurs preferentially in areas with greater rela- tive exposure index values (Garcon et al., 2010). Although it was not possible to record either wind velocity or wind direction in this study, the high-preference areas had taller waves during the nesting season, emphasizing the relation- ship between relative exposure index values and nesting distribution. Access to currents enables loggerhead turtle neonates
to escape rapidly from predator-rich coastal areas (Putman et al., 2010; Scott et al., 2014a,b). This means potentially that exposed beaches are of greater value for nesting.
Intra-beach nest site selection
At the intra-beach microhabitat level, female loggerhead tur- tles did not show a pattern of random re-nesting but rather a tendency to re-nest in areas with a medium or low risk of flooding/tidal erosion. Only a small per cent of female log- gerhead turtles re-nested in areas with a high risk of flooding and erosion. Significant consistency in nest site selection at the backs of beaches has been observed for other sea turtle species (Hays et al., 1995; Kamel & Mrosovsky, 2004, 2006; Patrício et al., 2018). This behaviour could be driven by environmental factors (e.g. sea turtles could detect whether sand humidity is below the necessary threshold or whether the beach slope ensures adequate nest elevation; Patrício et al., 2018). The location of the next nest of females that previously nested in an area of high flood risk is more likely to be in lower-risk areas. There are potential advantages of nesting in different beach areas, such as the variability of hatchling phenotypes that this type of nesting facilitates. Different temperature and water incubation regimes affect the size of hatchlings (Glen et al., 2003; Read et al., 2013), which leads to variability in predation rates, ultimately affecting fitness (Spencer, 2002;Wood et al., 2014). In addi- tion, as sea turtles have temperature-dependent sex deter- mination (Yntema & Mrosovsky, 1980; Chan & Liew, 1995; Chevalier et al., 1999; Godley et al., 2002), nests closer to the sea with lower incubation temperatures could produce more males despite the greater flood risk. Male sea turtle are of high conservation value in the context of anthropo- genic global warming, which is leading to the feminization of several populations (Jensen et al., 2018). Loggerhead turtles nesting on Maio Island are philopat-
ric but appear to use a bet-edging strategy, distributing their nests amongst several beaches. This could decrease the risk of losing all their nests in any adverse event on a single beach. This strategy has adaptive potential for the coloniza- tion of new, optimal incubation areas in the face of gradual environmental changes. Simultaneously, the choice of safe
Oryx, 2023, 57(2), 152–159 © The Author(s), 2022. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605321001496
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