High-Resolution Satellite and Archival Tracking of Leatherback Sea Turtles

Use of marine biologging devices enables the insight into the cryptic lives of marine fauna and the complex environment they inhabit. Using tracking and acoustic monitoring technologies deployed in tandem, we collected fine-scale data on the behaviour and acoustic environment of the leatherback turtle (Dermochelys coriacea), nesting in Gabon, Central Africa; a country which supports the largest leatherback nesting population in the world and 60% of all nesting leatherbacks in the Atlantic. A SPLASH10-AF satellite transmitter (Argos tracking), DSG-OpenTag (acoustic and movement) and VHF transmitter (for relocating individuals) were attached to four female turtles using direct carapacial attachment. Data were gathered throughout an entire internesting interval on depth-use, sound, location, and body movement. Here we combine spatial and sound datasets to define the marine soundscape of the nesting leatherback turtle (Chapter 1), whilst combining sound and movement datasets to investigate the effects of ambient acoustic environment on leatherback Vectoral Dynamic Body Acceleration (VeDBA; Chapter 2). Turtles encountered anthrophony (source: shipping activity; occurrence in acoustic files: mean ± SD = 74.7 ± 14.7%, n = 4 turtles; intensity: median = 128.2 dB re 1 µPa, n = 4202), loud noise events (events exceeding the 90th percentile, >135.5 dB re 1 µPa, n = 426), and biophony (source: humpback whale Megaptera novaeangliae vocalisations; occurrence in acoustic files: median = 114 vocalisations, n = 4) in the marine soundscape. VeDBA ranged from 0.005 – 0.171g and was significantly affected by depth and broadband sound energy (GLMM: χ21,6 = 8.62, p = <0.05) with individual turtle VeDBA influenced by different sound frequencies within the turtle hearing range. We discuss the potential effects of anthropogenic sound sources on this species and potential application of our methodologies. Our findings provide one of the first examples of animal-borne soundscape monitoring over extended periods (9 – 10 days; n = 4) a novel methodology for investigating the effects of marine acoustics on wild animal movement.