Horizontal and vertical movement behaviour of flatback turtles and spatial overlap with industrial development

Understanding the overlap of animal distributions and anthropogenic activity is essential for effective conservation management. Here, we analysed data from satellite transmitters deployed on 35 adult female flatback turtles nesting in the vicinity of an iron ore port to understand the spatial and temporal components of the main phases of their breeding cycle and assessed overlap with this industrial activity. During the inter-nesting phase, flatback turtles remained 14 ± 9 km from their nesting site. On their transit to foraging grounds they did not use a discrete corridor, using an area from the coast out to the 50 m contour and dispersed widely to foraging grounds (18 to 1326 km away) that had low spatial overlap among individuals. The home range of 94% of turtles during inter-nesting, 26% during outward transit and 3% during foraging had overlap with the shipping channel associated with the port. Although these results suggest that risks associated with vessel collision would be increased during the nesting season and early part of the transit to foraging grounds, no such impacts were detected. Outside of these times (>80% of the time), industrial activities in this area are likely to be low risk to flatback turtles from the main studied rookery. We also provide the first information on the diving behaviour and in situ water temperature data of flatback turtles during the post-nesting migration, showing that turtles forage both on the benthos and within the water column, and that some turtles forage in relatively deep and stratified water.