A dog who turns up on your doorstep might be cute and needy, leading you (or smaller members of your household) to say, "Can we keep it?" But before you start stocking up on fluffy beds and toys, realize that you are not free to take in a stray dog without first taking some preliminary steps.
You'll need to check into your local or state law. A simple online search or call to your city government should be enough to find out the requirements for dealing with stray animals.
Most likely, the law will mandate that you turn the dog over to the animal control authorities. They have the responsibility of trying to find the owner.
Or even if you're allowed to hang on to the dog, you might need to try to find the owner yourself. If you don't, you could be liable to the owner for the dog's value.
Common sense should also guide you: If the dog is healthy and well fed, someone is probably looking desperately for it. If it looks like it hasn't had a good meal or a bath in a while, it's unlikely that an owner is worried about it—or that it will be adopted if you leave it at a shelter.
Here are some basic steps to take if you need to track down the dog's owner:
You should not, unless there is an emergency, take it upon yourself to have the dog destroyed.
By way of example, there was a Louisiana man who found a sick puppy, which wasn't wearing a collar, in the front yard while he was visiting his father. He took the pup to a vet and, given a discouraging prognosis, two days later asked the vet to humanely destroy the dog. Only later did the dog's owners find out that the dog had been taken and destroyed. They sued and won the value of the dog. (Lincecum v. Smith, 287 So. 2d 625 (La. App. 1973).)
Taking responsibility for a pet is a no small thing. If you haven't made a dog part of your household before, you'll want to consider whether you have the time, resources, and patience to do so.
If you do feel ready, however, and your search for the true owner has turned up nothing, there might be lawful ways to keep it. If the law requires you to turn the dog over to animal control, ask for the first chance at adoption. Everyone has an interest in seeing that the dog finds a good home, and assuming you meet the criteria, that home might be yours.