Infrared Thermography in the Study of Animals' Emotional Responses: A Critical Review.

Tiziano Travain,Paola Valsecchi

doi:10.3390/ani11092510

Abstract

Simple SummaryAssessing animal welfare has proven to be a challenging task with important consequences for their management. In the last few years, infrared thermography has gained increasing scientific consensus as a method to analyze emotional reactions to different stimuli in different taxa. This review aims to explore particularly the use of infrared thermography in the assessment of animals’ emotions, mainly focusing on pets, laboratory, and husbandry animals. If properly used, this technique has proven to be a noninvasive, reliable method to identify emotional activations.Whether animals have emotions was historically a long-lasting question but, today, nobody disputes that they do. However, how to assess them and how to guarantee animals their welfare have become important research topics in the last 20 years. Infrared thermography (IRT) is a method to record the electromagnetic radiation emitted by bodies. It can indirectly assess sympathetic and parasympathetic activity via the modification of temperature of different body areas, caused by different phenomena such as stress-induced hyperthermia or variation in blood flow. Compared to other emotional activation assessment methods, IRT has the advantage of being noninvasive, allowing use without the risk of influencing animals’ behavior or physiological responses. This review describes general principles of IRT functioning, as well as its applications in studies regarding emotional reactions of domestic animals, with a brief section dedicated to the experiments on wildlife; it analyzes potentialities and possible flaws, confronting the results obtained in different taxa, and discusses further opportunities for IRT in studies about animal emotions.

Highlights

IntroductionInfrared thermography (IRT) is a remote and noninvasive method to assess the surface temperature of a body through the electromagnetic radiation emitted by any object with a temperature above absolute zero (i.e., 0 K, −273.15 ◦C)
Stress and pain responses have an influence on body temperature in different animals, and these responses can be monitored during different phases of husbandry processes such as routine handling practices [45,84], housing [43], or transport [40], in order to guarantee high welfare standards
Thermal data are a valuable tool for the assessment of animal welfare, and they could be integrated into an automated system for the early detection of ill or severely distressed animals [43,46]

Summary

Introduction

Infrared thermography (IRT) is a remote and noninvasive method to assess the surface temperature of a body through the electromagnetic radiation emitted by any object with a temperature above absolute zero (i.e., 0 K, −273.15 ◦C). Items on the earth’s surface emit radiation with a wavelength peak in the region of 10 μm, invisible to human eyes, it can be experienced as heat (e.g., 300 K, circa 27 ◦C, means a 9.5 μm wavelength peak) This means that we can see objects only because they reflect sunlight, while their own emitted radiation wavelength peak falls into the infrared radiation spectrum (700 nm–1 mm), which is why we refer to detecting it as infrared thermography [1]

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