title: Surfacers change their dive tactics depending on the aim of the dive: evidence from simultaneous measurements of breaths and energy expenditure.
abstract: Air-breathing divers are assumed to have evolved to apportion their time between surface and underwater periods to maximize the benefit gained from diving activities. However, whether they change their time allocation depending on the aim of the dive is still unknown. This may be particularly crucial for 'surfacers' because they dive for various purposes in addition to foraging. In this study, we counted breath events at the surface and estimated oxygen consumption during resting, foraging and other dives in 11 green turtles (Chelonia mydas) in the wild. Breath events were counted by a head-mounted acceleration logger or direct observation based on an animal-borne video logger, and oxygen consumption was estimated by measuring overall dynamic body acceleration. Our results indicate that green turtles maximized their submerged time, following this with five to seven breaths to replenish oxygen for resting dives. However, they changed their dive tactic during foraging and other dives; they surfaced without depleting their estimated stores of oxygen, followed by only a few breaths for effective foraging and locomotion. These dichotomous surfacing tactics would be the result of behavioural modifications by turtles depending on the aim of each dive.
authors.affiliation: Graduate School of Informatics, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan Field Science Education and Research Center, Kyoto University, Kitashirakawa Oiwakecho, Sakyo, Kyoto 606-8502, Japan okuyamajunichi@gmail.com.
authors.forename: Junichi
authors.initials: J
authors.lastname: Okuyama
authors.affiliation: Graduate School of Informatics, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan.
authors.forename: Runa
authors.initials: R
authors.lastname: Tabata
authors.affiliation: Graduate School of Informatics, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan.
authors.forename: Kana
authors.initials: K
authors.lastname: Nakajima
authors.affiliation: Graduate School of Informatics, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan Field Science Education and Research Center, Kyoto University, Kitashirakawa Oiwakecho, Sakyo, Kyoto 606-8502, Japan.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Arai
authors.affiliation: Research Center for Subtropical Fisheries, Seikai National Fisheries Research Institute, Fisheries Research Agency, Fukai Ota 148, Ishigaki, Okinawa 907-0451, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Nature and Science Programs, NHK Enterprises, Inc., Kamiyamacho 4-14, Shibuya, Tokyo 150-0047, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Kagawa
mesh_terms: D000818:Animals; D004242:Diving; D004734:Energy Metabolism; D007564:Japan; D010101:Oxygen Consumption; D056152:Respiratory Rate; D014426:Turtles / Q000502:physiology*
keywords: Chelonia mydas; biologging; diving physiology; metabolism; respiratory; sea turtle