Comparative Analysis of Vocalizations of Thoroughbred Mares (Equus caballus) between Estrus and Diestrus

Abstract

We investigated the differences between vocalizations of mares in estrus and diestrus, and determined the spectrographic parameters to discriminate estrus from diestrus. Thoroughbred brood mares (n=89) were exposed to a teasing procedure for 3 min and we recorded all of the vocalizations emitted from them. Among the mares, 56.5% of estrus and 78.6% of diestrus mares emitted calls toward approaching stallion which yielded higher tendency in occurrence rate of vocal responses in diestrus than estrus mares. We analyzed the spectrographic data of the mares (25 estrus and 22 diestrus mares) emitting calls as squeal toward approaching stallion. Based on the broad bandwidth spectrographic analysis, the duration and third formant of the call have a significant effect on discriminating estrus from diestrus.