Through their whinnies, horses convey specific information about their identities, including sex, height, and weight, according to French researchers. Acoustic analyses of whinnies and the reactions of horses to various recorded whinnies also suggest that the vocal calls play an important social role and appear to be unique to each horse.

This is the first study of its kind in horses, which are historically considered to be dependent on sight as opposed to hearing for their social communication, the researchers reported.

“Our laboratory focuses on the link between social bonds and auditory communication in various species, including birds, dolphins, and monkeys,” said Martine Hausberger, PhD, director of the Laboratory of Animal and Human Ethology, a branch of the French national research center (CNRS) and of the University of Rennes 1. “We realized there were practically no scientific publications on vocal communication among horses, despite the interesting social structure of these animals. We felt compelled to look into this, and what we found was that the whinny is a complex call full of relevant social information. It might even be a signature call for each individual.”

Characterized as a three-part call, with an introduction, climax, and end, the whinny varies in frequency according to sex, the study reported. Stallions have low-pitched frequencies whereas mare and gelding calls are higher. Interestingly, the two intact stallions of their study, which were subordinate to other stallions in their social group, also had high-frequency calls similar to that of mares, Hausberger’s team reported. All 30 horses in the study were either privately owned or belonged to a riding club