187
7.4.1 Hawksbill Nesting Grounds
We estimated the primary sex ratio of hawksbill hatchlings from incubation duration of 5514 in situ nests from 10 nesting beaches from two regions in Brazil over
the last 27 years. A strong female bias was estimated in all beaches, with 96% and
89% average female sex ratios produced in Bahia (BA) and Rio Grande do Norte
(RN). Both inter-annual (BA, 88–99%; RN, 75–96% female) and inter-beach (BA,
92–97%; RN, 81–92% female) variability in mean offspring sex ratio was observed
(Figs. 7.17 and 7.18).
7.4.2 Loggerhead Nesting Grounds
The primary sex ratio of loggerhead hatchlings was estimated from incubation duration of 27,697 in situ nests from 21 nesting beaches used by two subpopulations of
loggerhead turtles in Brazil over the last 25 years. A strong female bias (94%) was
observed in all the areas used by the northern loggerhead stock, Sergipe (SE) and
Bahia (BA), whereas a more balanced sex ratio (53% female) was estimated at the
regions used by the southern loggerhead stock, Espírito Santo (ES) and Rio de
Janeiro (RJ). Both inter-annual (SE: 83–99%, BA: 79.–98%, ES: 33–81%, RJ:
18–81%) and inter-beach variabilities (SE: 91–98%, BA: 89–96%, ES: 47–69%,
RJ: 28–55%) in mean female offspring were observed (Fig. 7.19).
7.4.3 Conclusions
These findings provide evidence of bias in the production of female offspring in
Brazil and significantly identify the beaches and months where males are produced.
Identify and enhance the protection of male-producing beaches has been highlighted as high priority to mitigate potential impacts from projected increases in
temperature on marine turtles (Hawkes et al. 2007, Fuentes et al. 2012, Marcovaldi
et al. 2014).
This outcome has prompted us to explore the thermal profile of nesting areas
used by loggerheads and hawksbills. For this, we deployed 60 data-loggers in 2013
along the whole extent of nesting areas and environments used by these species.
Thermal profile will be monitored over the course of several years and will be used
to estimate the current sex ratio being produced at each location. This data will be
coupled with climate models to predict future sex ratio and thus help prioritize management in light of global warming.
7 Novel Research Techniques Provide New Insights to the Sea Turtle Life Cycle
7.4.1 Hawksbill Nesting Grounds
We estimated the primary sex ratio of hawksbill hatchlings from incubation duration of 5514 in situ nests from 10 nesting beaches from two regions in Brazil over
the last 27 years. A strong female bias was estimated in all beaches, with 96% and
89% average female sex ratios produced in Bahia (BA) and Rio Grande do Norte
(RN). Both inter-annual (BA, 88–99%; RN, 75–96% female) and inter-beach (BA,
92–97%; RN, 81–92% female) variability in mean offspring sex ratio was observed
(Figs. 7.17 and 7.18).
7.4.2 Loggerhead Nesting Grounds
The primary sex ratio of loggerhead hatchlings was estimated from incubation duration of 27,697 in situ nests from 21 nesting beaches used by two subpopulations of
loggerhead turtles in Brazil over the last 25 years. A strong female bias (94%) was
observed in all the areas used by the northern loggerhead stock, Sergipe (SE) and
Bahia (BA), whereas a more balanced sex ratio (53% female) was estimated at the
regions used by the southern loggerhead stock, Espírito Santo (ES) and Rio de
Janeiro (RJ). Both inter-annual (SE: 83–99%, BA: 79.–98%, ES: 33–81%, RJ:
18–81%) and inter-beach variabilities (SE: 91–98%, BA: 89–96%, ES: 47–69%,
RJ: 28–55%) in mean female offspring were observed (Fig. 7.19).
7.4.3 Conclusions
These findings provide evidence of bias in the production of female offspring in
Brazil and significantly identify the beaches and months where males are produced.
Identify and enhance the protection of male-producing beaches has been highlighted as high priority to mitigate potential impacts from projected increases in
temperature on marine turtles (Hawkes et al. 2007, Fuentes et al. 2012, Marcovaldi
et al. 2014).
This outcome has prompted us to explore the thermal profile of nesting areas
used by loggerheads and hawksbills. For this, we deployed 60 data-loggers in 2013
along the whole extent of nesting areas and environments used by these species.
Thermal profile will be monitored over the course of several years and will be used
to estimate the current sex ratio being produced at each location. This data will be
coupled with climate models to predict future sex ratio and thus help prioritize management in light of global warming.
7 Novel Research Techniques Provide New Insights to the Sea Turtle Life Cycle