Deep-Voiced Stallions Are Most Appealing to Mares

Research conducted in The Netherlands indicated that mares are more interested in stallions with low-pitched whinnies.

In the study, stallion fertility was gauged by comparing the number of mares bred to number of pregnancies achieved. Hormonal levels were determined by blood analysis.

Stallions were shown mares in estrus and their whinnies were recorded and graded into high-pitched or low-pitched. Mares in estrus were placed between two speakers that broadcast contrasting whinnies. Mares turned their heads and bodies toward the low-pitched whinnies in preference to the high-pitched whinnies, and larger mares responded more often than pony mares to low-pitched whinnies.

When results were correlated, they showed that stallions with low-pitched whinnies had greater fertility than stallions with high-pitched whinnies. Although matings on a breeding farm are chosen by managers, mares in a natural setting might be drawn to the most fertile stallions, based on the tone and pitch of their vocalizations.