Physio-logging in Marine Animals: Recent Advances and Future Directions

Kagari Aoki^1*J. Chris McKnight²Takashi Kitagawa³

• ¹Teikyo University of Science, Uenohara, Japan
• ²University of St Andrews Sea Mammal Research Unit, St Andrews, United Kingdom
• ³Tokyo Daigaku, Kashiwa, Chiba, Japan

remotely measure and understand behavior and distribution, as well as environmental characteristics, physio-logging enables researchers to investigate physiological processes. This linkage between behavior, distribution, environment, and intrinsic physiology is crucial for the fields of ecology and conservation physiology (Cooke et al., 2021;Fahlman et al., 2021).Physio-logging has provided valuable insight into how animals respond to various environmental factors, such as the behavioral thermal adaptation of Pacific bluefin tuna Thunnus thynnus orientalis (e.g. Kitagawa et al. 2000Kitagawa et al. , 2022) ) and the behavioral response of homing chum salmon Oncorhynchus keta to varying ambient temperature structures (Kitagawa et al., 2016). Physio-logging can also provide the necessary tools for conservation management, which will contribute toward reducing the impacts of anthropogenic disturbances on species.For example, assessment of stress levels, such as measuring corticosterone, cortisol or heart rate, may help evaluate the impact of anthropogenic disturbance (e.g. Thompson et al., 2014, Lyamin et al.2016, Miksis et al., 2001). This potential has been demonstrated in recent studies across taxa: for example, tissue perfusion and behavioral conflict have been documented in grey seals Halichoerus grypus using physio-logging tools (McKnight et al., 2019). Similarly, Ponganis 2021 applied heart rate loggers to air-breathing animals such as a blue whale Balaenoptera musculus and emperor penguins Aptenodytes forsteri to monitor physiological effort during deep dives, revealing thresholds in oxygen management relevant to survival limits under environmental stress. Near-infrared spectroscopy has also been proposed by Ruesch et al.(2022) as a non-invasive tool to assess blood oxygenation in marine mammals, thereby opening new avenues for evaluating stress and health status under conditions of human care or environmental disturbance (Fahlman et al., 2021, Ruesch et al. 2022). This emerging era of physio-logging will enable long-term studies aimed at improving our understanding of In the future, as new sensors such as brain wave sensors are developed and big data recording and analysis technologies evolve, physio-logging will continue to evolve as a tool for measuring the physiological functions of marine organisms and will contribute to our understanding of the ecology of organisms on Earth, including ourselves.