behavior change in a horse

[LBHBHNCK <LBHBHNCK@FTC-I.NET>]

I need INPUT. My ten year old mare that has taught my grandchilred to
ride has recently developed a bucking habit...not every time she is
reidden, but often enough for me to knoe it is not being stung by a bee.
It has been, so far, only when we are almost back home, within a mile or
two, and at a canter. My vet thinks it may be hormones. Do any of you
have any idea?

Lucie Hancock and Tamar Starofdavid