Dear MARMAM community, My co-authors and I are pleased to announce the publication of our new paper examining heart rate in foraging harbor porpoises published in Proceedings of the Royal Society B: McDonald BI, Elmegaard SL, Johnson M, Wisniewska DM, Rojano-Doñate L, Galatius A, Siebert U, Teilmann J, Madsen PT. 2021. High heart rates in hunting harbour porpoises. Proceedings of the Royal Society B. 288: 20211596. https://doi.org/10.1098/rspb.2021.1596 Don't hesitate to get in touch with questions, comments and/or requests for a pdf. birgitte.mcdonald@sjsu.edu All the best on behalf of the authors, Gitte McDonald Abstract: The impressive breath-hold capabilities of marine mammals are facilitated by both enhanced O2 stores and reductions in the rate of O2 consumption via peripheral vasoconstriction and bradycardia, called the dive response. Many studies have focused on the extreme role of the dive response in maximizing dive duration in marine mammals, but few have addressed how these adjustments may compromise the capability to hunt, digest and thermoregulate during routine dives. Here, we use DTAGs, which record heart rate together with foraging and movement behaviour, to investigate how O2 management is balanced between the need to dive and forage in five wild harbour porpoises that hunt thousands of small prey daily during continuous shallow diving. Dive heart rates were moderate (median minimum 47–69 bpm) and relatively stable across dive types, dive duration (0.5–3.3 min) and activity. A moderate dive response, allowing for some perfusion of peripheral tissues, may be essential for fuelling the high field metabolic rates required to maintain body temperature and support digestion during diving in these small, continuously feeding cetaceans. Thus, despite having the capacity to prolong dives via a strong dive response, for these shallow-diving cetaceans, it appears to be more efficient to maintain circulation while diving: extreme heart rate gymnastics are for deep dives and emergencies, not everyday use. Birgitte I. McDonald Associate Professor Moss Landing Marine Laboratories San Jose State University 8272 Moss Landing Rd. Moss Landing, CA 95039 ----------------------------------------------- birgitte.mcdonald@sjsu.edu 831-771-4417