Using Infrared Thermography to Non-Invasively Assess Animal Health

Posted July 28, 2021 by Erin Curry

Erin Curry, PhD. CREW/Cincinnati Zoo & Botanical Garden, Cincinnati, OH
Michelle Shero, PhD. Woods Hole Oceanographic Institution, Woods Hole, MA
Caroline Rzucidlo, M.S. Woods Hole Oceanographic Institution, Woods Hole, MA

New project alert! We are excited for The Lindner Center for Conservation and Research of Endangered Wildlife’s (CREW) to start using remote infrared imaging to validate a completely non-invasive method of assessing animal health including obtaining concurrent heart rate, respiration rate, and body temp while capturing infrared thermography video from a diverse cross-section of species. In collaboration with Woods Hole Oceanographic Institution (WHOI), our goal is to image at least 50 different species from birds/reptiles through large mammals! The results of this project will further reinforce the Cincinnati Zoo & Botanical Garden’s reputation as a global leader in innovative conservation research.

The survival and reproductive success of an animal depends on the individual’s ability to efficiently manage energy stores despite large-scale intra- and inter-annual environmental variation.  Animals must achieve the caloric intake required to maintain metabolic costs, but environmental stressors may deleteriously impact these processes via reduced food availability and increased energy expenditures.

Monitoring animals’ responses to environmental changes is crucial, but traditional methods are invasive, logistically difficult, and costly. Simpler metrics such as respiration rate, heart rate, and body temperature are common proxies of metabolic rate and interest in developing non-invasive methods to evaluate animal health is growing. Accordingly, the use of infrared thermography (IRT) is being explored to assess vital signs in wildlife, as it previously has been utilized as a non-contact method to accurately measure heart rate in humans and domestic large animals through pulsation around the temples (Fig 1).

Recently, drone-operated IRT-derived heart rate measurements have been collected from wild cetaceans from blood flow to the dorsal fins; however, these values collected from wild cetaceans could not be validated (Horton et al. 2019). Similarly, in zoo-housed polar bears, our preliminary data indicate that both respiration rate and heart rate can be obtained using IRT (Fig 2) but, prior to field implementation, it is necessary to compare direct measures of vital signs to those obtained via IRT. Such measurements are challenging to obtain but zoological institutions can provide unique opportunities to validate these methods in a variety of wildlife species. Animals in human care are regularly immobilized for examinations and, during routine anesthesia monitoring, vital signs are usually recorded and can be compared to images/video obtained via IRT concurrently. In some cases, individual animals may even be trained for voluntary vital sign monitoring for comparison to metrics obtained via IRT.

A related application of IRT in wildlife and, especially zoo-housed animals, is reproductive monitoring. Pregnancy diagnosis, estrus detection, and changes in testicular thermal signatures may provide insight into the reproductive status, improve animal management, and facilitate more accurate timing of artificial insemination and semen collection procedures. Using non-invasive monitoring methods in awake animals or opportunistically during immobilizations, we propose to collect IRT images/videos of face/eyes, abdominal, and/or genital regions and correlate thermal signatures to known variables (pregnancy status, breeding season versus non-breeding season, phase of estrous cycle based on estrous/breeding behaviors or hormone monitoring, etc.) specific to the individual.

These activities will validate the accuracy of IRT in obtaining metrics of metabolic indices and reproductive status, non-invasively, across a variety of species. The data will be published in a scientific journal and may serve as a reference to both zoo and wildlife researchers.  Once validated, completely non-invasive thermal imagery could also then be used to remotely monitor individual animals and populations, as well their responses to potential stressors both in situ and ex situ.

Although IRT imaging has been used to locate and count various wildlife species, its application in assessing individual and population health, including reproductive status, is relatively novel. Validation of these methods is a critical step towards implementation in situ and zoos offer a unique opportunity for validation using a wide variety of species during anesthesia events. Ultimately, this technology will be paired with unmanned aerial systems (UAS/drones), which will allow data to be obtained from a greater number of individuals in a shorter period of time using entirely non-invasive remote sensing, allowing for detailed changes to be documented on a temporal scale. The information gained will allow researchers to determine how populations are responding to environmental challenges.