Introduction to the theme issue: Measuring physiology in free-living animals

Abstract

By describing where animals go, biologging technologies (i.e. animal attached logging of biological variables with small electronic devices) have been used to document the remarkable athletic feats of wild animals since the 1940s. The rapid development and miniaturization of physiologging (i.e. logging of physiological variables such as heart rate, blood oxygen content, lactate, breathing frequency and tidal volume on devices attached to animals) technologies in recent times (e.g. devices that weigh less than 2 g mass that can measure electrical biopotentials for days to weeks) has provided astonishing insights into the physiology of free-living animals to document how and why wild animals undertake these extreme feats. Now, physiologging, which was traditionally hindered by technological limitations, device size, ethics and logistics, is poised to benefit enormously from the on-going developments in biomedical and sports wearables technologies. Such technologies are already improving animal welfare and yield in agriculture and aquaculture, but may also reveal future pathways for therapeutic interventions in human health by shedding light on the physiological mechanisms with which free-living animals undertake some of the most extreme and impressive performances on earth. This article is part of the theme issue ‘Measuring physiology in free-living animals (Part I)’.

An accelerometer-derived ballistocardiogram method for detecting heart rate in free-ranging marine mammals

“…For example, BCGs extracted from gliding phases before and after controlled sonar exposure experiments could quantify the physiological response to anthropogenic disturbance ( Southall et al, 2019 ). Even as the field of physio-logging progresses with new hardware innovations ( Fahlman et al, 2021 ; Hawkes et al, 2021 ; Williams and Hindle, 2021 ), this method demonstrates that computational advances can derive new insights from traditional sensors.…”

“…Recent advances in physio-logging (recording physiological variables using animal-borne devices) have largely been driven by new developments in sensor technology ( Hawkes et al, 2021 ; Williams and Hindle, 2021 ). For example, new physio-logging tags can detect regional changes in blood flow by incorporating functional near-infrared spectroscopy sensors ( McKnight et al, 2021 ).…”

Pathogen surveillance and epidemiology in endangered peninsular bighorn sheep (Ovis canadensis nelsoni)

“…Advancements in machine learning could aid in image processing and automated detection of species, posture, and potentially even disease lesions (Tuia et al, 2022). “Physiologgers,” implantable transmitters that record physiologic variables such as heart rate, body temperature, and respiratory rhythms, are a rapidly developing technology that could one day be utilized to monitor bighorn sheep for signs of stress and sickness that may not be detected by visual observations alone (Hawkes et al, 2021). If these methods detected signs of morbidity or a decrease in apparent bighorn abundance, a more detailed investigation could be triggered.…”

How Reproducibility Will Accelerate Discovery Through Collaboration in Physio-Logging

“…Ecophysiology, like many other scientific disciplines, is undergoing a technological revolution fueled by advances in both hardware and software. One technology dramatically advancing the research boundary is physio-logging, which enabled observations of animals' physiology in the field using animal-borne sensors (Fahlman et al, 2021;Hawkes et al, 2021). Ecophysiologists suddenly find themselves with far more data, of increasing complexity, than ever before.…”