Our gentle 8-year-old dog growled and snapped at my son for the first time — do we have to rehome him?

A sudden change in behaviour in a previously stable adult dog is a medical problem until proven otherwise. The common hidden causes are pain (spine, hips, ears, teeth, an eye), failing sight or hearing — he is startled, not aggressive — and endocrine or neurological disease. Book a full veterinary exam and use the word aggression when you book, so they allow enough time. What you describe, slower on walks and grumbling as he gets up, fits a dog who is hurting.

Safety first, right now, and without punishment. Manage the space so the dog and the children cannot collide unsupervised: baby gates, a room of his own, a dog who is left to sleep undisturbed. And do not punish the growl. A growl is a warning, and a dog who is punished for growling learns to skip the warning and go straight to the bite.

Keep an incident log: date, time, exactly what happened in the ten seconds before, where the person's hands were, where the dog's body was — cornered, asleep, on the sofa, eating? Patterns fall out of that log fast. Take video of him sitting down and getting up, too.

If the exam is normal, your vet may still suggest a supervised trial of pain relief, because a dog who becomes tolerant again on it has told you the answer. Once the medical side is addressed, the next step is a qualified behaviourist working with your vet — not instead of them.

Please do not decide about rehoming this week. Get the exam first.