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Marine Ecology Progress Series

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MEPS 707:115-129 (2023)  -  DOI:

Polymorphic foraging tactics in a marine reptile: insight from horizontal movement and dive behavior analyses

Kento Fujita1, Hideaki Nishizawa1, Junichi Okuyama2,*, Mamiko Arita3, Shunichi Takuma4, Tomoko Narazaki5, Akemi Watabe4

1Graduate School of Informatics, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan
2Fisheries Technology Institute, Japan Fisheries Research and Education Agency, Fukai Ota 148, Ishigaki, Okinawa 907-0451, Japan
3Graduate School of Agriculture, Kindai University, Nakamachi 3327-204, Nara 631-8505, Japan
4Ichinomiya Sea Turtle Association, Ichinomiya, Higashino 32-11, Ichinomiya, Chosei-gun, Chiba 299-4306, Japan
5Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tenpaku-ku, Nagoya, Aichi 468-8502, Japan
*Corresponding author:

ABSTRACT: Life-history polymorphism in habitat use has been widely reported in aquatic migratory animals. Adult loggerhead sea turtles Caretta caretta in the North Pacific exhibit foraging-habitat polymorphism, showing a 2.4-fold greater reproductive output for neritic foragers than for oceanic ones. However, knowledge of how turtles in each habitat behave and what effect this has on reproduction remains limited. We combined horizontal movement and dive behavior analyses to explore foraging behavior and habitat utilization in adult female loggerheads in the North Pacific. Between 2016 and 2018, satellite relay data loggers were attached to 10 females nesting in Japan. The turtles were tracked for 219.2 ± 185.0 d (±SD) within the range of 10 to 521 d. Three foraging destinations were revealed, with different foraging tactics in each habitat: (1) the neritic East China Sea (ECS), (2) neritic coastal areas of mainland Japan (CMJ), and (3) oceanic North Pacific Ocean (NPO). ECS females mainly foraged on benthic prey with foraging-site fidelity; however, some turtles alternately preyed on benthos and plankton along with their seasonal migration. CMJ females also foraged on benthic prey with site fidelity, whereas NPO females foraged on plankton by drifting eastward with the oceanic currents. Dive-type analyses revealed that the proportion of time spent presumably foraging was similar among the 3 habitats, suggesting that the nutrient richness of prey items and the migration distance between foraging and breeding grounds may cause differences in reproductive outputs among different life-history types of loggerhead turtles.

KEY WORDS: Behavioral polymorphism · Foraging dichotomy · Intrapopulation variability · Loggerhead sea turtle · North Pacific · Satellite relay data logger · Satellite tracking · State-space modeling

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Cite this article as: Fujita K, Nishizawa H, Okuyama J, Arita M, Takuma S, Narazaki T, Watabe A (2023) Polymorphic foraging tactics in a marine reptile: insight from horizontal movement and dive behavior analyses. Mar Ecol Prog Ser 707:115-129.

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