Dr. Mona S. Miller lives in Lafayette with her 4 year old son, yellow Labrador Retriever and grey cat. She has worked at Four Seasons Animal Hospital in Lafayette since moving here in 2001. She attended Cal as an undergrad, and received her DVM from U.C. Davis. She can be reached at Four Seasons, 938-7700, or by email to MonaSDVM@aol.com.

The most recent publication of the Journal of the American Veterinary Medical Association contains an article, one of the first of its kind, that describes the effectiveness of microchips in returning lost animals to their guardians. A microchip is a rice-sized identification device that is implanted (injected) into the connective tissue under the skin, usually between the shoulder blades of a dog, cat or rabbit (in a bird it is injected into the pectoral musculature). It contains a bar-coded number that is read with a scanner, based on radio frequency technology. At the time of implantation (done by a veterinarian, shelter, animal rescue organization or breeder), the owner must register his/her personal information (name, address, contact phone numbers) with the microchip company. The idea is that if the pet were lost and scanned by a shelter, vet or rescue group, the owner can be traced via the phone numbers provided.
Injection can be performed without anesthesia (although I prefer to do this at the time of spay or neuter when possible, since the needle is big). The biggest "complication" I have seen, in over 20 years of veterinary experience, is that the microchip can migrate. This is important because the scanner should be held not only over the shoulders and back, but also on the sides and bottom of the chest when looking for a microchip. Experienced scanners are aware of this, and scan the animal in multiple spots.
In the study mentioned above, 53 shelters in 23 states participated during an 8-month time period, providing a total of 7,704 microchipped animals (this number includes 3,225 owner-relinquished animals, 4,083 strays and 396 "others"). The results of this study show that owners could be found for 74.1% of microchipped dogs and 63.5% of microchipped cats. The ability to find owners was higher for purebreds vs. mixed breeds, and for animals who were spayed/neutered vs. intact. Interestingly, animal shelters had a higher chance of finding an owner when the owner information was in the shelter's own database, and a significantly lower chance of finding an owner when it was left up to the owner to register with the microchip company. This underscores the importance of the crucial step of owner responsibility to register and keep current information with the microchip registry. In this study, the main reasons an owner of a microchipped animal could not be found were incorrect/disconnected telephone number, no response to telephone calls/letter sent by the shelter, or that the animal was registered to another group (such as shelter/veterinarian/rescue group who performed the implantation). In Canada and most countries in Europe, the services of microchipping and registering are bundled together. However in the United States these are treated as separate processes.