Heart rate as a measure of emotional arousal in evolutionary biology

Abstract

How individuals interact with their environment and respond to changes is a key area of research in evolutionary biology. A physiological parameter that provides an instant proxy for the activation of the automatic nervous system, and can be measured relatively easily, is modulation of heart rate. Over the past four decades, heart rate has been used to assess emotional arousal in non-human animals in a variety of contexts, including social behaviour, animal cognition, animal welfare and animal personality. In this review, I summarize how measuring heart rate has provided new insights into how social animals cope with challenges in their environment. I assess the advantages and limitations of different technologies used to measure heart rate in this context, including wearable heart rate belts and implantable transmitters, and provide an overview of prospective research avenues using established and new technologies, with a special focus on implications for applied research on animal welfare. This article is part of the theme issue ‘Measuring physiology in free-living animals (Part II)’.

Hot-headed peckers: thermographic changes during aggression among juvenile pheasants (Phasianus colchicus)

“…The ability to measure such physiological responses without any physical contact with the animals makes IRT potentially applicable to a wide range of systems, giving a clear advantage over other techniques that rely on implanted or wearable devices [31,46]. Previous avian IRT work has largely focused on the responses to acute non-social stressors [32,51] or long-term exposure to adverse health or welfare conditions [35,60,61], overlooking immediate short-term responses to the social interactions that establish and maintain dominance hierarchies.…”

“…Finally, as a complementary approach to all of these suggestions, it would be valuable to take thermographic measurements from interacting animals fitted with implanted devices, so that the data can be compared and validated against other, more established indicators of physiological arousal (e.g. heart rate [46] and core body temperature [31]).…”

“…We know far less about physiological responses to the more natural dominance interactions that occur spontaneously in larger groups. Implanted devices have been used to detect heart rate changes during aggression in free-roaming greylag geese (Anser anser) [45], but, as with studies of core body temperature, the practical and ethical challenges associated with invasive procedures limit their applicability [46].…”

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

“…For example, the portable and commercially available near infraRed spectroscopy data logging devices introduced in 2006 were originally designed for measuring muscle oximetry in sports athletes [49], but have now also been used to show anticipatory adjustments of blood flow prior to diving in seals [18,50,51]. A wide range of variables can be measured with current physiologging technologies, which includes heart rate [52][53][54][55][56], brain activity [57,58], tissue oxygenation [50,51], respiratory rhythms [59,60] and body temperature [61,62]. When measured simultaneously with other parameters (e.g.…”

What is physiologging? Introduction to the theme issue, part 2

“…The rapid development and increasing availability of technologies capable of monitoring and analysing heart rate in recent times [6] have been used to gain unique insights into animal welfare (e.g. farmed terrestrial and aquatic species [48][49][50][51]), to assess social interactions in animals [52][53][54][55] and to comprehensively understand the cardiorespiratory adaptations of breath-hold diving species [7,8]. A more recent physiologging variable is accelerometry, where the two-or three-dimensional acceleration of an animal is recorded at a temporal resolution that is sufficiently high to reveal individual wing or tail beats during locomotion [56][57][58][59].…”