Mare mounting another Mare

[Mahoganybay]

I have had my mare just coming up to 3 years and have never seen her do this before.

Went to bring her in from field when she walked up to another mare (who was winking & quite obviously in season) curled her lip, started grunting and licking her and then mounted her, she was thrusting at her too.

This only lasted about 30 seconds and then she got off, i then caught her, brought her into her stable and put her back out about 10 mins later and she did exactly the same thing, and with the same mare.

My mare is in season too.

Anybody have any experience of this, she is the top horse in an all mare field of about 10.

Is it normal behaviour?

 

[sonjafoers]

I've honestly no idea if it's normal but when my mare was quite young (up to the age of about 5 I think) she used to do it to my other older mare. My older mare is lead mare so I'm surprised the youngster tried it on but she did - despite getting a severe telling off from my older mare. She used to try & do it quite regularly but has since grown out of it. I don't know if either or both were in season when she used to do it but seeing as she has gown out of it I'm guessing it was hormone related.

 

[sykokat]

This is normal behaviour amongst mares that are in season. Bitches do it as well. I would only worry if it went on for too long and the risk of getting kicked or damage from shoes was possible.

 

[Donkeymad]

As cougar says, perfectly normal behaviour between in-season mares. Don't worry about it.

 

[JanetGeorge]

This is normal behaviour amongst mares that are in season.

No, it's not! VERY occasionally you'll see weanling/yearling fillies do it when they first come into season, but in older mares, (unless they're in foal!) the most likely cause is an ovarian tumour called a Granulosa Theca Cell tumour. This type of tumour is benign, but it does produce testosterone and make mares behave like stallions!

In brood mares, there is a stage of mid to late pregnancy where the foetus is secreting large amounts of steroids, and testosterone is one of those steroids. That makes its way into the mare's system, and she may develop stallion-like behaviour - it passes.

Assuming your mare is not pregnant, I would speak to your vet about having your mare's ovaries scanned because if it IS a GTC tumour, it will just get bigger and cause pain - and possibly very aggressive behaviour! Treatment is removal of the ovary (and the tumour) - usually via a flank incision and done standing.

 

[Mahoganybay]

Thanks for replies, in all the years i have owned horses, i have never seen a mare do that to another mare, it wasn't nice to watch.

JanetGeorge, my mare is 8 years old and definitely not pregnant so i suspect that it could be a Granulosa Cell Tumor, she exhibits some of the other symptoms too, i.e. low-grade lameness, very nappy & confident out riding, irritable when ridden sometimes, ears back when girthing (even though saddle & back ok).

Will give the vet a ring & see about getting her scanned.

 

[zandp]

My youngster did it to my elder mare last year, normally when I'd be trying to catch the elder one. She was 4 and then and now chases my elder mare away from me, she used to chase her away and then mount her, I always thought it was a dominance thing. This year she's only been chasing the elder one away. My elder mare is more passive.

 

[RSL]

I would say its normal, after all, girls don't have to like boys and vice versa lol

 

[JanetGeorge]

Thanks for replies, in all the years i have owned horses, i have never seen a mare do that to another mare, it wasn't nice to watch.

JanetGeorge, my mare is 8 years old and definitely not pregnant so i suspect that it could be a Granulosa Cell Tumor, she exhibits some of the other symptoms too, i.e. low-grade lameness, very nappy & confident out riding, irritable when ridden sometimes, ears back when girthing (even though saddle & back ok).

Will give the vet a ring & see about getting her scanned.

No - it's not. A friend's mare started doing it last year - on a rather 'ratty' livery yard. She had abusive 'phone calls from other mare owners. Mare had a HUGE GTCT which was successfully removed - nad my friend found a nice small yard to rent to get away from the ratbags!

I too have owned mares for more than 50 years - and currently have about 20 mares and about 15 fillies from 1-3. They don't do it at all!! (we won't talk about some of my colts!!) The other symptoms together with the mounting would seem pretty conclusive.

The only thing that makes it not 100% sure is that your mare was in season. Normally, once a GTCT is big enough to cause 'stallion' behaviour, the mare is NOT coming into season at all because of the testosterone levels - a scan will show one enlarged ovary - and the other is MUCH smaller than normal and inactive. But mares don't read the gynaecology manuals - and there are always variations from the 'classic' cases.

 

[MyBoyChe]

Have read this thread with interest as a mare on our yard started to do this last year, she had been covered but was thought not to be in foal. One evening I walked through the yard where they were kept and she was literally chasing the other mare around the yard until she had her cornered, then mounting and trying to cover her! Both were in an absolute muck sweat and it was quite frightening to witness. I separated them and put them in their boxes where they both settled down. The next day she was at it again so again they had to be kept apart. Later that week she was re scanned and found to be 5 months in foal. The mares owner has owned horses for over 40 years, bred many foals and had never seen anything like this before so JanetGeorges comments are really interesting. They were kept separate for about a month and then turned back out together, we have had no problems with either since and the foal is due in the next couple of weeks.

 

[Fairynuff]

No - it's not. A friend's mare started doing it last year - on a rather 'ratty' livery yard. She had abusive 'phone calls from other mare owners. Mare had a HUGE GTCT which was successfully removed - nad my friend found a nice small yard to rent to get away from the ratbags!

I too have owned mares for more than 50 years - and currently have about 20 mares and about 15 fillies from 1-3. They don't do it at all!! (we won't talk about some of my colts!!) The other symptoms together with the mounting would seem pretty conclusive.

The only thing that makes it not 100% sure is that your mare was in season. Normally, once a GTCT is big enough to cause 'stallion' behaviour, the mare is NOT coming into season at all because of the testosterone levels - a scan will show one enlarged ovary - and the other is MUCH smaller than normal and inactive. But mares don't read the gynaecology manuals - and there are always variations from the 'classic' cases.

So nice to see someone who knows what they are talking about. Sadly there are far too few left on HHo. Agree with you 100% Janet.

 

[Donkeymad]

I can only apologise for my error. Normally I do not reply unless I am 100% certain. Obviously this time my answer was clouded by my knowledge of donkeys, in which this behaviour is VERY normal.