High dive efficiency in shallow water

Dive studies across mammals, birds, reptiles, and fish often focus on deep dives, and shallow-water diving has tended to be overlooked. For air-breathers, foraging in shallow water poses challenges since the lungs generate buoyancy, and shallow divers must trade off the extent of inhalation against the negative buoyancy needed to avoid floating to the surface. Using high-resolution depth loggers, we addressed this knowledge gap around the ecology of shallow water diving at a foraging site for hawksbill turtles (Eretmochelys imbricata) where depth was typically <3m. Contrary to predictions, dive durations were long, particularly at night (mean dive duration per turtle: 17-61 min, n=12 turtles, n=2576 nocturnal dives), despite warm water temperatures (24-37oC). Dive efficiency (% time submerged) for hawksbills was 98%, the highest recorded for any air-breathing marine vertebrate including penguins (60-78%), seals (51-91%), cetaceans (68-87%), and other sea turtle species (68-95%). Hawk..., High-resolution time-depth recorders (TDRs) were deployed on hawksbill turtles foraging in Turtle Cove at the southern tip of the horse-shoe-shaped lagoon of Diego Garcia atoll in the Chagos Archipelago, Indian Ocean (7.42oS, 72.46oE), during October 2012 (n=5) and February to March 2021 (n=7). Turtles were captured at low tide in shallow water (<1 m) by approaching slowly and carefully from behind before seizing the carapace, whereupon turtles were carried ashore. The curved carapace length (CCL) and curved carapace width (CCW) were measured using a flexible tape, and mass recorded with a suspended scale (Pesola Macro line 50 kg scale, Pesola AG, Switzerland). Maximum precision TDRs (G5 data loggers, 10 bar sensors with 0.03 m resolution, Cefas Technology Limited, Lowestoft, UK) were attached proximally to the trailing edge of flippers, using wire ties to fix them onto flipper tags placed at the thin junction between adjacent thick flipper scales (Supplementary Information Fig. S1)...., Any software that can open .txt files, for example Excel, R, etc.,