MEASURING EMOTIONS IN WORKING DONKEYS USING EYE TEMPERATURE, SPONTANEOUS BLINK RATE, AND HEART RATE VARIABILITY

Quantitative measures of emotion are important for objectively assessing animal welfare. However, there is no research on emotion in donkeys. We used 34 donkeys to investigate eye temperature (ET), spontaneous blink rate (SBR), and heart rate variability (HRV) as measures of stress and positive emotions. ET, SBR, and HRV were measured using a FLIR thermographic camera, a GoPro camera, and a Polar heart rate monitor, respectively. Donkeys were subject to three different treatments: positive, negative, and control. The positive treatment was provision of high-quality lucerne, and the negative treatment was the sound of clippers close to the donkey’s ear. Donkeys in their current living environment without positive or negative treatment were used as the control. We collected nine minutes of data per donkey, three for each treatment. The data was analyzed using a linear mixed-effects model and Pearson correlation. SBR increased significantly with the positive treatment compared to control (18.94±5.83 to 37.94±8.37 blinks per min, p<0.001), and decreased significantly with the negative treatment compared to control (18.94±5.83 to 12.20±5.89 blinks per min, p<0.001). A significant increase in ET was found for negative treatment compared to control (34.55±0.93 to 35.75±0.99°C, p<0.001). HRV was significantly higher with positive treatment compared to control (47.26±17.52 to 80.23±27.23 ms, p<0.001). There was a significant strong negative correlation between change in ET and HRV between control and negative treatment (r = -0.71, p<0.001). A significant moderate negative correlation was found between change in ET and HRV between control and positive treatment (r = -0.59, p<0.001). A significant moderate positive correlation was demonstrated between change in SBR and HRV between control and negative treatment (r = 0.54, p<0.001), and a significant moderate positive correlation was found between change in SBR and HRV between control and positive treatment (r = 0.56, p<0.001). ET and SBR correlated with HRV, which is a standard and conventional measure of stress and emotion in horses and other mammalian species. Stressful situations can cause increased ocular vasodilation, leading to higher ET. Additionally, positive events cause a rise in SBR due to the increased release of dopamine. We demonstrated the use of ET, SBR, and HRV as a measure of stress and positive emotions in working donkeys. We have shown that SBR is a simple, valid, and quick way to measure stress and positive emotions in donkeys without the need for sophisticated equipment, which is important in low-resource settings.