Presentation of binning-based inter-click interval data from passive acoustic monitoring of free-ranging harbour porpoises (Phocoena Phocoena)

C-PODs are used for Passive Acoustic Monitoring (PAM) of harbour porpoises (Phocoena phocoena) at an offshore open sea location in the German North Sea. The amount of data obtained allows a fine-scale data classification. Diel patterns of echolocation click trains are extracted from minimum inter-click interval (minICI) data by binning. The aim of this study is to reassess and refine minICI ranges of click train data with particular consideration to the binning widths. Emphasis is also placed on choosing an appropriate visualisation of these binned data. Key ecological results include presence of higher train rates during the day with intermediate minICI values defined by the range (7-27)ms and a higher train rate with short minICI values (1.25-2.25)ms at night. This indicates an increase in porpoise feeding behaviour, or change of style, at night. Click trains with long minICI values >35ms occur at an equal rate throughout both diel phases, suggesting a more routine behaviour, such as navigation. The results could be obtained only by judicious choice of binning widths. The classification methodology can be used to analyse echolocation trains from a variety of odontocete species and can be applied to any PAM data with the relevant click parameters.