This thesis advances the understanding of the spatial and behavioural ecology of two endangered species, basking sharks (Cetorhinus maximus) and green turtles (Chelonia mydas) at their coastal foraging sites while highlighting the pragmatic application of biologging technology in informing conservation. Chapter 1 of this thesis is a general introduction to tracking technologies, covering how the advancements of biologging have revolutionised the field of ecology, with an emphasis on how accelerometers can be used in conservation. Chapters 2 explores the use of accelerometers on three basking sharks in the western Scottish Isles to understand their fine-scale behaviour. I present early evidence of potential behavioural lateralisation, and the first direct records of 67 breaches over 41 days, with sharks breaching on average twice a day, both during night and day and increasing energy expenditure by at least 30 times to breach. While the function of breaching remains unclear, owing to its energetic cost, breaching is likely to have an important fitness function. In Chapter 3, accelerometers were deployed on 16 juvenile green turtles in the Bahamas to investigate the behavioural and energetic costs of translocation. Turtles rehomed in as little as 15 hours following translocation of 4 km and allocated twice as much time to energetically demanding behaviours compared to resident turtles at their foraging grounds, highlighting that translocation is not a suitable conservation practice for sea turtles. Chapter 4 summarises both data chapters and discusses how their findings provide further evidence of how tracking technologies can be ideal tools for conservation practitioners by monitoring animal movement, behaviour and health as well as assisting with the designation of protected areas by identifying important life history events. Chapter 4 concludes on the challenges and limitations of the thesis as well as the future directions in the use of tracking technologies in conservation ecology.