Foraging of the green sea turtle Chelonia mydas on seagrass beds at Mayotte Island (Indian Ocean), determined by acoustic transmitters

Abstract

We studied the foraging rhythms of green sea turtles Chelonia mydas on the seagrass beds of N'Gouja Bay, Mayotte Island (Comoros Archipelago) with acoustic transmitters and moored listening stations. We monitored 8 tagged turtles (4 probable males, 3 probable females and 1 immature), from 70 to 109 cm curved carapace length (CCL), for durations ranging from 5 to 92 d. The turtles exhibited a regular diel pattern: they foraged mainly during the day (on average 87% of seagrass detections were between 06:00 and 18:00 h) and rested on the inner reef slope during the night. Night time feeding activities were observed on the seagrass bed when the night light was high. The presence of turtles on the seagrass bed at night was significantly correlated with a night light index (r = 0.54, p = 0.002), which included both moon light and cloudiness indices. Behaviour of the only immature individual observed was similar to adult turtles, although it rested more frequently around noon. All turtles displayed a high fidelity to 1 foraging site within the seagrass bed. Acoustic transmitters and permanent listening stations are an appropriate technique for long-term behavioural studies of turtles, with no human interaction with turtles during tracking, and represent a suitable technique to assess the possible effects of environmental changes or human activities upon green turtle behaviour.

Trading shallow safety for deep sleep: juvenile green turtles select deeper resting sites as they grow

“…data). Bjorndal (1980) reported anecdotal observations of green turtles feeding on 'bright, moonlit nights ' and Taquet et al (2006) noted that turtle presence in the seagrass foraging area was positively correlated with an ambient light index. Although 2 turtles in our study exhibited multiple nights of high activity levels in the shallows likely associated with foraging, these animals were not tagged during the same period, and other animals carrying tags at the same time showed resting behavior on these nights.…”

Movement patterns of juvenile hawksbill turtles Eretmochelys imbricata at a Caribbean coral atoll: long-term tracking using passive acoustic telemetry

“…Movements of turtles can be linked with predation (Heithaus et al 2008, Hammerschlag et al 2015, environmental change (Pike 2008, Schofield et al 2009), or anthropogenic pressure, to distinguish what factors affect turtle foraging, migration, and development (Taquet et al 2006, Heithaus 2013. While our study has provided valuable data regarding the movements of juvenile hawksbill turtles around an offshore developmental habitat, other methods of long-term monitoring, such as satellite telemetry and stable isotope analysis, would permit insights even if tracked individuals were to leave the atoll (Shimada et al 2014).…”

Energy expenditure of freely swimming adult green turtles (Chelonia mydas) and its link with body acceleration

“…Comoros Islands, Mayotte Island, Scattered Islands) Lauret-Stepler et al, 2007). For example, at Mayotte Island juvenile and adult green turtles exploit seagrass meadows on a yearround basis (Taquet et al, 2006;Ballorain et al, 2010). Similarly, at Reunion Island foraging juvenile and adult green turtles are present in coral reef zones throughout the year (Jean et al, 2010).…”