Lima, A. F., Lima, S. G. C., Nogueira-Filho, S. L. G. et al. 2022. Vocal expression of emotions in farmed spotted paca (Cuniculus paca). Applied Animal Behaviour Science 256, 105753.

Vocal emissions in non-human mammals can be used as non-invasive indicators of animal emotion and welfare. Therefore, we aimed to validate the use of acoustic parameters as indicators of affective states and welfare in farmed spotted paca (Cuniculus paca). We recorded the vocalizations of 36 pacas, living in 12 groups (two females and one male/group), during four distinct experiences that were assumed to generate different affective states (negative, positive, ambiguous, and highly positive). Spotted pacas emitted more snorts, either as single elements or phrases, when experiencing a negative affective state. Four acoustic parameters of snorts, roars, and barks, which were recorded during all experiences, differed according to the affective valence assumed to be experienced by the spotted pacas. During the negative condition – morning cleaning routine spotted pacas emitted many more snort calls, which are characterized by a shift in the mean amplitude towards a higher level of intensity and as well as by a shift in the energy distribution (Q75) towards a higher frequency than those emitted in the positive condition compared to those emitted in the assumed positive valence condition – feeding time with the regular diet. These call-characteristics, along with the increase in the mean amplitude of snort calls from the lowest to the highest arousal levels, may thus reflect negative affective state and arousal in spotted paca. Therefore, the increase in the overall emission of snorts together with changes in their acoustic parameters may be valuable as indicators of negative emotions of C. paca, and thus have potential as an automated and non-invasive tool for welfare assessment in this species.