Rationale: Locomotion is energetically demanding, consuming energy at high rates compared to other activities. The overall energetic costs of locomotion is important to the animal’s survival and can be measured directly in the laboratory by analysing the exhaled air. Measuring energy use directly in the field is difficult, but it should be possible to use proxies (e.g. heart rate, heat generation and body acceleration) to estimate metabolic rate. However, the underlying assumptions and simplifications inherent in these indirect approaches have not been rigorously assessed and validated.
The overall aim of the project is to determine how muscles are used during locomotion and how this determines the overall amount of energy used during exercise. These measurements will underpin efforts to develop methodologies for estimating energy expenditure in freely living birds.
Plan of work and impact of our studies: To achieve this, we will determine energy use of the whole organism by measuring the gases exhaled during exercise in a wind tunnel (flying) or on a treadmill (running), while simultaneously recording heart rate, body acceleration, heat production and limb movements. The distribution of blood around the body during exercise will be used to indicate energy use by all of the muscles and by other, non-muscular physiological systems (e.g. breathing, circulation). The mechanical output of the locomotory muscles will be determined by combining measurements of their behaviour during locomotion with muscle contractile measurements in the laboratory. Ultimately, we will establish the detailed relationship between whole organism and tissue-level energy use with that of proxies of energy turnover that can be measured in the field. These integrated measurements will allow us to refine and improve the predictive power of using such proxies as indicators of energy use and will provide a firm footing for understanding animal locomotory behaviour in the field. This information will be useful in helping to explain current changes in population and species distribution, provide inspiration towards the development of bio-inspired robotics and in developing and refining computer models of animal movement, ultimately, contributing to the replacement, reduction and refinement of animals in research.
Animal welfare: The variety of physiological techniques that have been selected are the most suitable approaches currently available for acquiring the data required. Some discomfort may be experienced from the presence of internal sensors and from the surgery, but this is expected to be short-lived. Appropriate group sizes are used to identify statistically significant differences between groups, whilst minimising the number of animals undergoing the protocol. Group sizes will be constantly reviewed during the project to ensure the minimum number of animals are used.