Seasonal Variations in Heart Rate Variability as an Indicator of Stress in Free-Ranging Pregnant Przewalski's Horses (E. ferus przewalskii) within the Hortobágy National Park in Hungary

Przewalski's horses (Equus ferus przewalskii) in Hungary's Hortobágy National Park exhibit seasonal stress patterns, as indicated by decreased heart rate variability (HRV), particularly during winter and spring. This novel finding, derived from telemetric HRV measurements, reveals that these free-ranging mammals experience heightened allostatic load—likely due to limited resources in winter and increased energy demands during pregnancy or dietary transitions in spring. Unlike traditional stress indicators like glucocorticoid levels, HRV provides a non-invasive, long-term method to study undisturbed cardiovascular responses in wildlife. The study employed implanted transmitters to continuously monitor HRV, heart rate (HR), body temperature, and activity over a year, offering insights into the physiological challenges faced by mammals in seasonal ecosystems.

Pohlin, F., Brabender, K., Fluch, G., Stalder, G., Petit, T., & Walzer, C. (2017). Seasonal Variations in Heart Rate Variability as an Indicator of Stress in Free-Ranging Pregnant Przewalski’s Horses (E. ferus przewalskii) within the Hortobágy National Park in Hungary. Frontiers in Physiology, 8. https://doi.org/10.3389/fphys.2017.00664