Do mares get along better in groups of mares? Is there more fighting in mixed groups of mares and geldings? Horse farm managers have differing opinions and practices on this matter.
A 2009 research study conducted in Norway examined this question. The goal was to test the effects of sex separation in turnout groups by analyzing injuries, social interactions, and proximity to other horses. The study used 66 horses split into 18 groups, in paddocks and pastures of varying size. There were mares-only groups, geldings-only groups, and mixed-sex groups. The horses were predominantly Icelandic horses, warmbloods, and Norwegian Fjords.
Injuries were assessed on a scale of 0 (no visible wounds/injuries) to 5 (extensive and serious injury) for each horse on the first day after the groups were introduced, and once four to six weeks later. Lameness was similarly scored on a scale from 0 (no lameness) to 2 (very lame).
Social interactions were observed twice daily for one hour, for three days, for to six weeks after group introduction. Behaviors were categorized into 19 interactions falling under “aggressive interactions,” “friendly interactions,” “greeting behaviors” and “other behaviors.” They also recorded the minimum distance between horses.
Results
The experiment showed no significant differences between mare groups, gelding groups and mixed-sex groups in social interactions. While there were aggressive interactions observed in all groups, they were mostly threats that did not result in physical contact between horses. One behavior had somewhat of a significant difference; mare groups appeared to engage in less “play” behaviors than geldings or mixed groups.
There were no significant differences in the number or severity of injuries between the groups, either on the first day or four to six weeks later. Very few injuries were found, and none were serious. No lameness was observed at all.
Finally, they found no significant differences between groups when it came to horse spacing. Most of the time, horses were within 6 feet of their closest neighbor regardless of sex.
This study concluded that the sex makeup of the herd did not affect behavior, injuries or proximity to other horses.
Other considerations
This is valuable information for horse farm managers, although, of course, there are some other factors to consider. Stallions were not included in this study because breeding was not desired. Generally, stallions should not be turned out with mares (unless breeding is desired) or geldings.
Individual horse temperaments can dictate group makeup. Two extremely dominant horses may not be able to live together, even if they are the same sex. A horse’s turnout history could affect how it reacts in different turnout groups.
Use good judgment when creating turnout groups and make sure to watch the herd the first few times they are turned out together. Often, the group will work out their own dominance hierarchy within a few days or weeks. Signs that the group is not working include severe fighting and continuous chasing of other horses.
Tips for Gradually Introducing a New Horse to a Herd
• Quarantine all new horses for three weeks to ensure no contagious diseases spread to your horses.
• Turn the new horse out by itself in view of the new group for a while.
• Allow the new horse to meet the herd by stalling them next to each other or letting them touch noses over a safe fence line.
• Remove hind shoes if horses in the herd are known to kick.
• Turn the new horse out with herd members one by one so that they each get a chance to meet individually.
• Minimize resource guarding by providing multiple waterers and hay stations far apart.
• Remember that some posturing and threatening is completely normal as the horses sort out their place in the herd.
Source: Grete Helen Meisfjord Jørgensen, Linn Borsheim, Cecilie Marie Mejdell, Eva Søndergaard, Knut Egil Boe. Grouping horses according to gender —Effects on aggression, spacing and injuries. Applied Animal Behaviour Science. Volume 120, Issues 1–2. 2009. Pages 94-99. ISSN 0168-1591. doi.org/10.1016/j.applanim.2009.05.005.
