We have all of our cats and dogs micro-chipped. The challenge is that there are multiple companies that make the chips and track animals and not every vet or animal control location will have the proper "readers" for all the different chips. So they may pick up a dog for example that has a chip, but they can't read it and so they assume the dog doesn't have one.

It just goes under the skin on the back of the pet and you can't tell they have and it doesn't bother them at all. It might a bit sore for a day after installation, but then they are fine. If you are dealing with kidnapping, you might want to consider tattoing (which I know is done, but don't know any more about). Otherwise make sure all your pets also wear an identifying tag on their collars at all times. We do this as well. Hope it helps a little bit.

~Critterkids