It’s pretty easy to tell when a dog’s nervy around strange people. He’s jumpy and on the alert: either he can’t sit still and is constantly fidgeting, leaping at the smallest sound, and pacing around barking and whining; or he’s very still indeed, sitting rock-steady in one place, staring hard at the object of his suspicions (a visitor, the mailman, someone approaching him on the street while he’s tied up outside a store.)
Why does it happen?
There’s one major reason why a dog doesn’t like strange people: he’s never had the chance to get used to them. Remember, your dog relies 100% on you to broaden his horizons for him: without being taken on lots of outings to see the world and realize for himself, through consistent and positive experiences, that the unknown doesn’t necessarily equal bad news for him, how can he realistically be expected to relax in an unfamiliar situation?
What can I do about it?
The process of accustoming your dog to the world and all the strange people (and animals) that it contains is called socialization. This is an incredibly important aspect of your dog’s upbringing: in fact, it’s pretty hard to overemphasize just how important it is. Socializing your dog means exposing him from a young age (generally speaking, as soon as he’s had his vaccinations) to a wide variety of new experiences, new people, and new animals.