| Budget Amount *help |
¥23,660,000 (Direct Cost: ¥18,200,000、Indirect Cost: ¥5,460,000)
Fiscal Year 2017: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
Fiscal Year 2016: ¥10,920,000 (Direct Cost: ¥8,400,000、Indirect Cost: ¥2,520,000)
Fiscal Year 2015: ¥10,660,000 (Direct Cost: ¥8,200,000、Indirect Cost: ¥2,460,000)
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| Outline of Final Research Achievements |
This study approached the mechanism of migration dichotomy (neritic v.s. oceanic) of loggerhead sea turtles (Carretta caretta) nesting in Japan. We conducted the satellite tracking of the turtles nesting at the northern and southern area to figure out which turtles migrate to the neritic/ oceanic habitat. In addition, we analyzed the stable isotope ratios of egg yolk to estimate the ratio of habitat types in each nesting population. Our results indicate that loggerhead turtles nesting at any nesting beaches ordinarily show the migration dichotomy: larger turtles migrate to the neritic foraging area, while smaller migrate to the oceanic foraging area. The ratio of the habitat type demonstrated that almost all of the southern nesting populations were neritic type, meanwhile the ratio of oceanic type gradually increased with the northern populations. This fact indicates that ocean environment around the nesting beach may be involved in the formation mechanism of migration dichotomy.
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