We explored the potential of thermal imaging and artificial intelligence (AI) in animal emotion research. Thermal cameras play a vital role in obtaining and collecting large volumes of multidimensional data, and AI has the capabilities of processing and extracting valuable information from these data. The amount of data collected using thermal imaging is huge, and automation techniques are therefore crucial to find a meaningful correlation between animal emotional state and changes in body temperature.
This research developed a pipeline to automatically extract the maximum temperature from a selected region of interest (RoI) from thermographic images collected in pigs. The base of the ear of pigs was chosen as RoI in this study, as it is proposed as an important area in emotion research (Boileau et al., 2019; Lu et al., 2018). This RoI can be observed well from a top view which was, thus, how the thermal camera was installed. The developed pipeline consists of three stages. The first one checks whether the RoI is completely visible to extract the thermal temperature. If so, the second stage detects and segments both ROIs (left and right ear base) from the frame. In the last stage, the maximum temperature is extracted from the segmented RoIs, which is subsequently saved in an external file together with frame number.
The thermal imaging videos were captured during a frustration challenge test, which was part of a larger experiment to study resilience in pigs (see for more details Luo et al., 2022). The experiment was conducted at Carus, the animal research facility of Wageningen University & Research, Wageningen, the Netherlands. A total of 373 female pigs (TN70 x Tempo) were tested in the frustration challenge. For this challenge, each pig was taken out from its home pen and moved to a small pen (1.2x0.6mtr) in a test room for 10 minutes. Here, the isolated animal was able to see and hear other pigs exploring and playing freely in a “play arena”. The inability to join the playing pigs may have induced a feeling (emotion) of frustration. A FLIR T1020 thermal imaging camera was mounted on a tripod with a distance of about 1mtr between the pig’s head and the camera. A total of 373 thermal imaging videos were recorded during the test.