Modelling endurance in free-ranging animals using tracking collars: insights from domestic hunting dogs

Endurance is crucial for animal survival yet remains poorly studied in free-ranging animals. An animal's endurance time decreases as a hyperbolic function of increasing exercise intensity, called the speed-duration relationship. This relationship allows for defining critical speed, the endurance threshold separating efforts where metabolic homeostasis is achievable from efforts where fatigue accumulates drastically. Using tracking collars on domestic dogs during hunting sessions, we demonstrated the ability to determine the speed-duration relationship and its parameters: the initial speed (Si), critical speed (Sc) and distance reserve (DAC,max). This new method exhibits good repeatability across sessions and bypasses conventional laboratory assessment, allowing the characterisation of physical capacities in natura. Our approach provides the unique possibility to study when, where and how long free-ranging animals experience fatigue and helps uncover how environmental factors affect their energy expenditure.