ID Chips
It is possible to inject a tiny microchip hardly bigger than a grain of rice into your animal. If it’s a dog, cat or rabbit this will be into the scruff of the neck. This can be done at any age. Microchipped dogs and cats are given a collar tag to show that they have been microchipped - this acts as a deterrent to thieves. Most commonly dogs and cats are implanted, but microchipping is suitable for small mammals, reptiles, birds and fish.
If your pet should go missing, most vets, animal charities and local authorities have microchip readers so when someone hands your pet in, they can read the unique microchip code. This identifies your pet on a central database so that you can be contacted and your pet returned.