There is a difference

observable also in the neighings of
horses. That is to say, the female foal has a thin small neigh, and
the male foal a small neigh, yet bigger and deeper-toned than that
of the female, and a louder one as time goes on. And when the young
male and female are two years old and take to breeding, the neighing
of the stallion becomes loud and deep, and that of the mare louder and
shriller than heretofore; and this change goes on until they reach the
age of about twenty years; and after this time the neighing in both
sexes becomes weaker and weaker.