Ivan is trying to hump Skye!!!

He's been at it all morning!!
They are both neutured. I am quite dismayed by it I have to admit. I am terrified he will hurt her I mean he is a giant and she is a toy mix. Usually they play fine together. There has never been a grumble or any sort of disagreement of any kind between them so I am at a loss as to why this is happening.
This is the first time I have ever had two dogs together let alone two of different sexes.
He keeps trying to grab her scruff and then crouches into position. I keep letting a roar at him to stop but then he comes back for more. She doesn't seem to bothered either way and tells him off if he gets too far.
But surely neither of them should be interested if they have been done.
Has anyone else ever experienced this
Thanks
Nic xx

IT has nothing to do with sex..............

Yeah I kind of thought this. Any idea how long it will go on for?

My staffie (Male) was done last year. i looked after a female dog this year for a couple of months and he kept trying to hump her. it wasnt a dominance thing as he didnt try this with my male AB. but i do undetstand it does drive you crazy as, as soon as your backs turned there at it again!

My Jessie(who is spayed)likes to hump Roodee(Cavalier)she liked to hump him before she was spayed as well.

Thanks guys.
Makes me feel a bit better.
It's just Ivan never showed any interest in doing this up til now. Not even before she was spayed. She is about a year old now.
I am so afraid of him hurting her accidently as he is usually such a gentle giant.
Might this stop as soon as it started or will this continue now.
Should I try to nip it in the bud or let them sort it out themselves.
She does seem to tell him off a bit but I mean if he really wanted to she wouldn't stand much chance.

id stop it now. you just cant risk it with him being so big! when asbo was doing it to daphni, id clap my hands really loud and say no. he soon stopped. now i just have to say no and he stops straight away.

i wouldnt leave them alone together while you are out (if you do) just to be on the safe side.

Thanks guys for all the replies xx