Temperature Tactics: Investigating Heart Rate Variability and Behavioural Responses in Rats under Thermal Stress

Abstract Thermal stress has a significant impact on heart rate variability (HRV), reflecting the autonomic nervous system’s responses to environmental temperature changes. The mammalian behaviour is also known to be very sensitive to changes in environmental heat. This study experimentally evaluated the effects of thermal stress on heart rate variability (HRV) and behavioural responses in rats. In parallel, a synthetic data–driven computational framework was developed to explore generalised relationships between temperature, HRV, and behavioural indices. Eighty young male Wistar rats were divided into (a) Hyperthermia (exposed at 42°C) (n = 40) and compared with (b) Control (exposed at room temperature 24 ± 1°C) (n = 40). HRV was assessed using electrocardiogram recordings, allowing a detailed analysis of the activity of the autonomic nervous system. During the same time, behavioural evaluations were conducted to evaluate changes in activity levels, anxiety-like behaviours, and social interactions. Although real rat electrocardiographic (ECG) and behavioural data were recorded under thermal stress, these experimental data were not used for machine learning (ML) training. The ML model was trained exclusively on synthetically generated HRV data and is intended as a conceptual modelling framework rather than a predictor of individual rat physiology. The model was trained solely on synthetically generated HRV data. The findings indicate a significant correlation between temperature exposure and changes in HRV, with higher temperature leading to decreased variability, suggesting increased activation of the sympathetic nervous system. Behavioural observations revealed elevated anxiety-related responses and reduced exploratory behaviour in rats exposed to extreme thermal conditions. These results highlight the complex interplay between environmental stressors and physiological responses, providing insight into the adaptive mechanisms used by rats in the face of extreme temperatures. This research contributes to a better understanding of how thermal stress influences both physiological and behavioural health in mammals, with implications for managing animal welfare in changing environments.