The behaviour analysis was done with the professional software Observer XT as well as Pocket Observer. The CPOD data was pre-processed in custom-made software (Chelonia Ltd., UK; http://www.chelonia.co.uk/), after which selected parameters were exported to a computer for further processing. The PCL data was processed by the custom made prototype software Aquaclickview (Aquatec group Ltd., UK; http://www.aquatecgroup.com). The average clicks per hour recorded from both the PCLs and the CPODs were exported for further analysis. All data was analysed with Microsoft Excel and SPSS.