Mare mounting another mare WDYT..

Tess Love

Tess Love

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My friend and I keep our mares together who are both in their late teens and although they like each other they tend to keep there distance from each other most of the time. A new younger mare arrived on the yard recently who hates being on her own so we agreed for her to go in with our girls, they are all good doers and the field in plenty big enough. All was fine until I noticed my mare had come into season and then my friends mare also came into season and now the young mare keeps mounting both our girls. I've never known this and just wondered if anyone could enlighten me??
 
It happened with a mare I had, she acted very stallion like & was mounting one other particular mare! I called the vet as I was worried she had a Granulosa Cell Tumour, as she was very mareish anyway.

Vet came & performed a rectal examination, nothing untoward was found. He said just to keep an eye on her. I never saw her do it again.

I came to the conclusion it was a dominance thing as she was the herd leader.
 
My first loan horse when I was 15 began mounting other mares when she herself came into season. I presume because she had been a broodmare for a few years previously. At the same time her behaviour changed and she refused to be caught, would be very grumpy (bitey/nippy) and in the end returned to her owner (a riding school owner/instructor) although she wasn't used in the school.
 
It does happen, often a dominant mare in season may try this. Its not usual but can often worry owners, usually an overload of hormones.
My little mare had another popped in with her earlier this year, and this brought her in season earlier and she spent just under a day leaping on and off the other mare. They did settle well after, for the following 3 weks the extra one was with me
 
at my old yard we had a mare who did this. She had an ovarian tumour which sent her hormones all over the place. She was a very dominant mare anyway but in the end she had to be pts as the tumour became so large.
 
My mare is definitely the most dominant one and that doesn't seem to of changed but it all very consensual between the 3 of them as it were!
 
I had my mare and stallion running together and a couple of months before the mare was due to foal she started mounting the stallion. He didn't mind in the least. She'd stopped before she foaled and never did it again.
 
One of my mares will do it if she's in with certain other horses. It's never bothered me; she's an ex broodmare so I always knew there were never any internal oddities, it's just her and how she interacts with some other mares.
 
Frumpoon said:
Quite common, just dominance, try not to worry unless it looks injurious
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Disagree, sorry.

Dominance - if it has anything to do with it - is, I believe, incidental. It is certainly not normal dominance behaviour for horses. It seems much more likely to me that the cause is hormonal - specifically an increase in testosterone producing stallion-like behaviour. The aggressiveness that testosterone engenders (no pun intended) could explain why a mare would show more dominance behaviour too, since aggression or threats of aggression is how dominance is expressed. Tess Love, does the young mare that you described come into season regularly herself?
 
fburton said:
Disagree, sorry.

Dominance - if it has anything to do with it - is, I believe, incidental. It is certainly not normal dominance behaviour for horses. It seems much more likely to me that the cause is hormonal - specifically an increase in testosterone producing stallion-like behaviour. The aggressiveness that testosterone engenders (no pun intended) could explain why a mare would show more dominance behaviour too, since aggression or threats of aggression is how dominance is expressed. Tess Love, does the young mare that you described come into season regularly herself?
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exactly the case in the mare at my old yard. The vet said it was due to the increased testosterone levels because of the tumour.
 
One of my mares starting mounting her mother a few years ago out of the blue. She was squealing and acting very stallion like when parted from her. I put her on Oestress and she went back to her normal self. I dropped the Oestress this year to see what would happen and she seems fine still so not sure why she was like it for that year.
 
fburton said:
Dominance - if it has anything to do with it - is, I believe, incidental. It is certainly not normal dominance behaviour for horses. It seems much more likely to me that the cause is hormonal - specifically an increase in testosterone producing stallion-like behaviour. The aggressiveness that testosterone engenders (no pun intended) could explain why a mare would show more dominance behaviour too, since aggression or threats of aggression is how dominance is expressed.
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Totally off on a bit of a tangent here but FB do you have any links to any studies which may have been done on this? I'd be interested to read it. One thing I find of interest is, I own 6 female dogs; 3 are spayed and 3 are entire. 4 of them 'bonk' each other, either way around, they don't seem to care who's on top. There is a distinct hierarchy obviously as they've lived together their whole lives but other than musing about them all being girls it has never bothered me, nor has it caused any problems within their relationships with one another, hence my interest in whether a study has ever been done.
 
fburton said:
Disagree, sorry.

Dominance - if it has anything to do with it - is, I believe, incidental. It is certainly not normal dominance behaviour for horses. It seems much more likely to me that the cause is hormonal - specifically an increase in testosterone producing stallion-like behaviour. The aggressiveness that testosterone engenders (no pun intended) could explain why a mare would show more dominance behaviour too, since aggression or threats of aggression is how dominance is expressed. Tess Love, does the young mare that you described come into season regularly herself?
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I'm with fburton on this! I have a LOT of mares - about 20 who are either breeding/just retired from breeding and about 30 youngsters from weanling to 4 years old. The ONLY thing I see is a bit of 'flirting' when some are in season. That doesn't include mounting.

If the mare isn't coming into season herself, I'd be wanting her checked out for a Granulosa theca cell tumour!
 
fburton said:
Disagree, sorry.

Dominance - if it has anything to do with it - is, I believe, incidental. It is certainly not normal dominance behaviour for horses. It seems much more likely to me that the cause is hormonal - specifically an increase in testosterone producing stallion-like behaviour. The aggressiveness that testosterone engenders (no pun intended) could explain why a mare would show more dominance behaviour too, since aggression or threats of aggression is how dominance is expressed. Tess Love, does the young mare that you described come into season regularly herself?
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Hi fburton I'm not sure if she's in season but apparently another mare who is opposite her when stabled but no where near her field wise has also come into season now too. Today my friends mare was calling for her when they were apart and again letting her mount her. The other thing she did before being with our girls was break out of her field to get to a young gelding who was only cut about 9 months ago. I'm convinced she being treated like a stallion by our girls. The vet is due on Tuesday for an unrelated matter but going to get some advice.
 
I have six mares and some of mine mount others when they are in season. My 14.3hh mounts my 9.3hh!!!
It is more common than many think, an sadly I have no idea how to stop it.
 
Spring Feather said:
Totally off on a bit of a tangent here but FB do you have any links to any studies which may have been done on this? I'd be interested to read it.
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On testosterone and stallion-like behaviour, or aggression and dominance? For both, it's a pretty standard observation that will have been reported in a number of papers and review articles. (There's been a lot published on granulosa cell tumours.) What did you want to know specifically?

Tess Love said:
Hi fburton I'm not sure if she's in season but apparently another mare who is opposite her when stabled but no where near her field wise has also come into season now too. Today my friends mare was calling for her when they were apart and again letting her mount her. The other thing she did before being with our girls was break out of her field to get to a young gelding who was only cut about 9 months ago. I'm convinced she being treated like a stallion by our girls. The vet is due on Tuesday for an unrelated matter but going to get some advice.
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Good luck - I'd be interested to hear what your vet thinks!

happyclappy said:
I have six mares and some of mine mount others when they are in season. My 14.3hh mounts my 9.3hh!!!
It is more common than many think, an sadly I have no idea how to stop it.
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It happens, for sure, but is pretty uncommon. I'd say mounting behaviour happens in a fraction of a percent of all mares, so it should be considered abnormal. As mentioned above, an ovarian (granulosa-theca cell) tumour would be the first cause to consider.
 
fburton said:
On testosterone and stallion-like behaviour, or aggression and dominance? For both, it's a pretty standard observation that will have been reported in a number of papers and review articles. (There's been a lot published on granulosa cell tumours.) What did you want to know specifically?
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Information in relation to my (non-aggressive nor dominant) female dogs bonking each other :)
 
Spring Feather said:
Information in relation to my (non-aggressive nor dominant) female dogs bonking each other :)
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Oh, I see - sorry! :redface3: TBH, I know rather less about dog behaviour than that of horses, but I do know that female mounting is quite common. One hears it said that in dogs it's 'a sign of dominance' - and it may well be - although I'm always sceptical of such statements when applied to horses.

As for studies on the behaviour, I found the following paper published in 1968 on "the effects of estrogen on mounting by females" that references some older studies, including the original report of the behaviour by Beach in 1967. Here's the abstract:

"Female dogs mounted other females more frequently when the 2nd bitch was in estrus, but the hormonal state of the mounting individual had little influence upon mount frequency; estrogen rendered a female more provocative or stimulating and more cooperative or receptive to mounting by another dog. During heterosexual tests estrous females tended to mount males selectively, responding readily to some masculine partners and never mounting others; in limited tests anestrous females did not mount males. Estrogen facilitated expression of specific feminine copulatory reactions and increased tendencies to display various positive social responses to dogs of either sex. Whether or not the hormone directly enhanced the female's tendency to mount a conspecific partner was not determined."

If you like I'll send you a copy of the full paper.
 
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