Time and tide : seasonal, diel and tidal rhythms in Wadden Sea Harbour porpoises (Phocoena phocoena)

• Published in: PLOS ONE
• Main Authors: Zein, Beate, Woelfing, Benno, Dähne, Michael, Schaffeld, Tobias, Ludwig, Stefan, Rye, Jacob Hansen, Baltzer, Johannes, Ruser, Andreas, Siebert, Ursula
• Other Authors: University of St Andrews. School of Geography & Sustainable Development
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: GC Oceanography; QH301 Biology; E-DAS; GC; QH301; Harbour porpoise; Phocoena phocoena
• Online Access: http://hdl.handle.net/10023/17348; https://doi.org/10.1371/journal.pone.0213348

The study was partly funded by the Schleswig-Holstein’s Government-Owned Company for Coastal Protection, National Parks and Ocean Protection, Wadden Sea National Park Administration of Lower Saxony (Richard Czeck) and the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (FKZ: 03 275 20 and FKZ: 0329946B). This publication was supported by Deutsche Forschungsgemeinschaft and University of Veterinary Medicine Hannover, Foundation within the funding programme Open Access Publishing. Odontocetes have evolved a rich diversity of prey- and habitat-specific foraging strategies, which allows them to feed opportunistically on locally and temporally abundant prey. While habitat-specific foraging strategies have been documented for some odontocete species, this is less known for the harbour porpoise (Phocoena phocoena). We collected multiple years of acoustic data using echolocation click loggers to analyse porpoise occurrence and buzzing behaviour, indicating feeding, in the German Wadden Sea (North Sea). Seasonal, diel and tidal effects were studied using Generalised Estimating Equations (GEE-GAMs). Locally season, time of day and tidal time significantly influenced the probability of porpoise detections and detection of foraging sequences (buzzes). Hunting strategies, and therefore frequency of buzzes, were likely affected by prey distribution and large differences between POD locations indicated that porpoises used highly specific behaviour adapted to tide and time of day to efficiently feed on the available prey. Strong seasonal and spatial variation in diel and tidal effects underline the importance of long-term observations. Studies on porpoise behaviour are often based on short-term observations and might rather reflect a seasonal than a general pattern. The results of this study show clearly that significant changes in porpoise behaviour can be found in short and long-term observations. Here some features are based on short term determinants and others are stable over years and ...