The reason why the shelter does this is because the shelter wants to return as many stray dogs as possible. At our local shelter, they have to kill an average of 500 dogs and cats every month because of overcrowding. Any dog or cat that they can return to its owner is one less animal they have to kill. Tags on collars can get lost or mangled. The microchip can’t get lost and will last for decades. And it is so small about the size of a grain of rice that the dog doesn’t even know it is there.

The technology behind these chips is fascinating. They are called Radio Frequency Identification, or RFID, chips. Sealed inside a tiny glass cylinder is an even tinier radio transmitter along with an incredibly small computer. The computer contains the unique ID number. It sends the number to the radio transmitter, which broadcasts it to the scanner. Obviously this tiny radio is not very powerful, so the scanner has to be just an inch or two away for it to pick up the transmission. But it is a transmission nonetheless. So the scanner picks up the radio’s signal, decodes the number and displays it.

But where do the computer and radio transmitter get their power? There is no battery embedded in the dog’s neck. This is the ingenious part of an RFID chip. The scanner actually sends out a fluctuating magnetic field into the dog. The RFID chip contains another antenna that picks up this magnetic energy and converts it into electricity. This electricity then powers the computer and radio transmitter. So the dog’s chip is sitting there, doing nothing, until a scanner comes along. The scanner provides the chip with the wireless power it needs to send out its unique ID number. Then the chip goes dormant once again.

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