I wonder if anyone can help us please? Up until  a week ago, Hank was a very social dog with us and stayed with us and followed us everywhere. Now as soon as we are up he wants to be out the back garden on his own just sitting and staring at nothing in particular and occasionally howling at sirens. In all weathers. When he does come in for the night he stays on his own  and doesn't socialise with us much. He's not aggressive and will come when called. I don't know what up. He's not neutered.  HELP!

If it happened suddenly i would bring him to the vet. A sudden change could be a medical issue thyroid problems in particular are known for temperament changes. Could be something happened in the house could even be a nearby female coming into heat. A long time ago we had a springer spaniel that got major depression and he became a recluse that wouldnt come inside. Tried several anti depressants in the end he just became an outside dog. It was his choice he was not banned from the house or anything. Later he developed the spaniel genetic predisposition to go violently crazy for no reason and ended up being put to sleep for biting a child during one of his rages. Ive learned that nothing with dogs happens suddenly unless its a trauma or medical issue or in the case of an un neutered male a nearby bitch in heat

Not being fixed it could be a female but usually unfixed males have a bit of a restlessness to them when a female comes into heat. Age could play into it as well. Young dogs go through a change as they mature. they go from excited about everything to just mellowing out and it can happen around 3 years old or a bit older. Some do it younger. Some never mature. lol. As long as he is eating properly, pottying habits haven't changed, still likes to get out and go for his walks, I wouldn't worry too much unless it's as Lostmaniac says and was a fast change. Like one day he's bouncing around, happy-go-lucky, and the next he's distant and depressed acting.

I changed the name of your thread slightly so as to distinguish this one from your intro thread. that should help with getting more feedback.

Thank you for both things.