Deep-Diving California Sea Lions: Are They Pushing Their Physiological Limit?

Abstract

This project will contribute to our understanding of oxygen management and the underlying physiological mechanisms of oxygen management in marine mammals. This information is essential if we are to interpret and understand the limits of dive performance, foraging ecology, and the ability of breath hold divers to adapt to environmental change and disturbance. The concept that most dives are aerobic in nature and do not exceed an aerobic dive limit (ADL -dive duration associated with the onset of post-dive blood lactate accumulation) has dominated the interpretation of dive behavior and foraging ecology over the past 30 years (Kooyman et al., 1980;Costa et al., 2001). However, because of technical difficulties, the ADL has rarely been measured. Instead, researchers have had to resort to estimations of total O 2 store depletion, i.e., calculated ADLs (cADLs) (Costa et al., 2001;Weise and Costa, 2007). In this study we will determine the rate and magnitude of O 2 store depletion during dives, and investigate its relationship to heart rate and workload, thereby improving our understanding of O 2 management during diving, specifically the role of lung O 2 stores and O 2 delivery to tissues. OBJECTIVESThis study will utilize backpack digital recorders to measure blood oxygen depletion, heart rate, and flipper stroke rate in dives of California sea lions during maternal foraging trips to sea from San Nicolas Island. The goals of this research are 1) determination of the rate, pattern and magnitude of blood O 2 store depletion during both shallow and deep dives at sea, 2) documentation of heart rate profiles of shallow and deep dives, and assessment of the relationship between changes in heart rate to blood O 2 profiles, and 3) documentation of flipper stroke rate profiles during shallow and deep dives, and assessment of the relationship of stroke rate to both changes in heart rate and changes in blood O 2 profiles. APPROACHObjective 1: In order to calculate the rate and magnitude of depletion of the blood O 2 store during dives, arterial P O2 profiles will be obtained from a P O2 recorder and intravascular electrode deployed on

Methods for Monitoring for the Population Consequences of Disturbance in Marine Mammals: A Review

“…Information on features such as the presence of rake marks and epidermal lesions, which may be useful for health assessment and individual identification, can also be collected during visual surveys ( Supplementary Table S4). New tools are being developed to monitor the physiology of animals and estimate physiological states and body condition remotely using telemetry (e.g., Ponganis and McDonald, 2015;Williams, 2015;Elmegaard et al, 2016;Ponganis, 2017;McDonald et al, 2018;Costa et al, 2019;Fahlman et al, 2019;Madsen and Van Der Hoop, 2019). Transmission of this information via satellite could allow longitudinal monitoring of these variables over a period of months (Miller et al, 2019).…”