In order to be able to at least understand what she's going through and hopefully answer questions from the peanut gallery with some aplomb I decided to do some research, so here's some of the stuff I've learned about the equine estrous cycle:
- Mares have what's called a Seasonal Polyestrus Cycle. This means that during part of the year (usually spring to fall but depends on the length of days) they have multiple estrus (heat) cycles.
- These estrus (heat) cycles usually last around 6 to 7 days and occur every 15 to 16 days (diestrus or NOT in heat), making the full estrous (estrus + diestrus) cycle about 21 to 22 days long (that's just a little shorter than human femles), although this can vary from mare to mare.
- The gestation period for a foal to develop from conception to birth is about 11 months, thus mares stop ovulating (and thus don't go through estrus) in winter in order to not give birth at the harshest time of year.
- The most apparent signs that a mare has entered estrus (is in heat) are more frequent urination, lifting her tail and "winking" her vulva, squatting as if to urinate but without urinating and permitting or even encouraging a stallion's presence. Some mares may also be a lot crankier or even agressive toward other mares, geldings and humans.
Here are some articles about mares in heat for further reading:
- Hormones and Horses: The Mare's Estrous Cycle. From Yahoo Associated Content.
- The Normal Equine Estrous Cycle. From Vetmed.lsu.edu.
- The Mare's Estrous Cycle. From Equine-Reproduction.com.
- Mare in Heat Q and A. From UltimateHorseSite.com.
- How to Tell if a Mare is in Heat. From Horsekeeping.com.
- Managing Heat Cycles in Mares. From Equisearch.com.