Mace's behaviour has shocked me..

Mace for the most part is a dream dog - toilet training finally sunk in, hes brilliant on and off lead, perfect with all humans and dogs (will wait calmly until is invited to say hello), does as hes told, has improved LOADS with regards to his food guarding - and is a joy to own.

- only I feel a new problem is starting, one I am not comfortable with

Yesterday had the dogs in the garden (the gardens being done so people are in and out!) a friend from over the road popped in was stood with us for about 30mins the other side of the temporary fence and lent over to give me a cuddle before leaving and Mace flew at her, barking his head off I was totally shocked, as was my friend who has seen him since he was a pup. I yelled 'get in' and think I did just in time, I am not sure if he would have connected with her or not if given the chance

Today mum chucked a towel at me and before I could catch it to put in the washing machine Mace did just the same as the night before, totally went mad at it!

I dont understand where this has come from, or why! Is Mace 'protecting' ??
any advice would be great, as this is something I dont want happening - I have always felt I had total control over him, but now I am doubting it ...

I would say a vet check just to be on the safe side, any sudden odd change in behaviour could be based on a medical issue. Not "omg quick book him into the emergency BH vet" but keep an eye on him and have a checkup sooner rather than later just to rule it out

Louie went through this phase of barking at strangers and even me a couple of times if I was up the garden and he didn't recognise me from the distance.
Perhaps it's a collie thing. I don't have much experience in collies but Louie seems to have grown out of it - he only barks at strangers now - well I don't mind that as long as he shuts up when told.

How old is he now? 9-10 months?

He was only at the vets a few days ago, had a quick check over while we got some wormer. But I can always go back and ask for a more indepth check, and mention his change in behavious - thanks

Mace isnt barking at strangers though its just this one person who edged towards me and he knows her Hes totally fine with strangers, we had two people here for hours picking up a rescue pup and he didnt batter an eye lid other than to sneak on the sofa for sloppy kisses.

He will be 10 months on the 28th.

Perhaps it is a protecting instinct then..not sure although BC's are my favourite breed, I cannot really give you an answer as I have never owned one (only half a one)

Could it be that he didn't like the way your friend was moving - her body language?

Dogs go through the second fear imprint period/fear of new situations phase between about 6 and 14 months, different ages for different dogs. Dogs may show fear of new situations and/or even familiar situations and be reluctant to approach someone or something new. It is important that you are patient and act very matter of fact in these situations. Never force the dog to face the situation. DO NOT pet the frightened puppy or talk in soothing tones. The puppy will interpret such responses as praise for being frightened. Training will help improve the dog's confidence.

So I would not get too OTT about it, just make a mental note of places/people/times and frequency.

not sure he showed no signs, came out the blue! All she did was, lean forward

Ok thank you. When he acts in this way, how am I meant to correct the behaviour, show him its not wanted or accepted? I feel that the towel being thrown to me could have spooked him - hence the reaction, but because of the incident the night before I think it could be something more than that, I shall keep an eye and hope theres nothing more to it.

Have you desensitised your dog to people hugging you or throwing tea towels around?

If not, maybe it is time to start..........

Whilst I do not believe in coercion for competition training, I am afraid there is no room for argument re domestic manners etc.

So tell him that this behaviour is not acceptable, in a manner which gets your message across but does not increase his fear; only you know what that is.