Dive heart rate in harbour porpoises is influenced by exercise and expectations

• Published in: Journal of Experimental Biology
• Main Authors: McDonald, Brigitte, Johnson, Mark, Madsen, Peter
• Other Authors: European Commission, University of St Andrews.School of Biology, University of St Andrews.Marine Alliance for Science & Technology Scotland, University of St Andrews.Sea Mammal Research Unit, University of St Andrews.Sound Tags Group, University of St Andrews.Bioacoustics group, University of St Andrews.Scottish Oceans Institute
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2018
• Subjects: Diving physiology; Bradycardia; Dive response; Harbour porpoise; Heart rate regulation; Exercise; QH301 Biology; QL Zoology; DAS; QH301; QL; Phocoena phocoena
• Online Access: https://hdl.handle.net/10023/16420; https://doi.org/10.1242/jeb.168740; http://jeb.biologists.org/content/early/2017/11/08/jeb.168740

This research was supported by a National Science Foundation International Research Postdoctoral Fellowship (OISE – 1159123 awarded to B.I.M.); and grants from the Office of Naval Research (N000141410416) and the Carlsberg Foundation (awarded to P.T.M. and B.I.M.). MJ was funded by a Marie Curie Sklodowska Career Integration Grant and by the Marine Alliance for Science and Technology Scotland. Data are available from figshare digital repository at 10.6084/m9.figshare.5549329 The dive response, a decrease in heart rate (ƒH) and peripheral vasoconstriction, is the key mechanism allowing breath-hold divers to perform long duration dives. This pronounced cardiovascular response to diving has been investigated intensely in pinnipeds, but comparatively little is known for cetaceans, in particular in ecologically relevant settings. Here we studied the dive ƒH response in one the smallest cetaceans, the harbour porpoise (Phocoena phocoena). We used a novel multi-sensor data logger to record dive behaviour, ƒH, ventilations and feeding events in three trained porpoises, providing the first evaluation of cetacean ƒH regulation while performing a variety of natural behaviours, including prey capture. We predicted that tagged harbour porpoises would exhibit a decrease in ƒH in all dives, but the degree of bradycardia would be influenced by dive duration and activity, i.e., the dive ƒH response will be exercise modulated. In all dives, ƒH decreased compared to surface rates by at least 50% (mean maximum surface=173 beats min−1, mean minimum dive=50 beats min−1); however, dive ƒH was approximately 10 beats min−1 higher in active dives due to a slower decrease in ƒH and more variable ƒH during pursuit of prey. We show that porpoises exhibit the typical breath-hold diver bradycardia during aerobic dives and that the heart rate response is modulated by exercise and dive duration; however, other variables such as expectations and individual differences are equally important in determining diving heart rate. Peer reviewed