Microchipping – permanent identification of your dog

Stray dogs and cats are a big problem in many countries and the emotional cost, to owners and pets, can be huge.

Dogs may be walked off-lead, making it easy for them to stray or be stolen, escape from yards, or jump fences. A collar and tag are common but are easily slipped or broken. Microchips are a more permanent solution, and are a legal requirement in many countries. They provide a quick and efficient way to reunite owners with their lost pets, even across international frontiers. Ear tattoos are another form of permanent identification, but these are now no longer widely used due to the more accessible alternative of microchips.

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According to a study of over 7,700 stray animals in over 53 shelters in the US, dogs without microchips were reunited with their owners only 21.9% of the time and cats only 1.8% of the time. However, cats with microchips were reunited with their owners 38.5% of the time and microchipped dogs were returned home 52.2% of the time. While the US does not legally require microchipping, it has been a legal requirement for all dogs over eight weeks old in the UK since 2016. This is in line with similar legislation in many European countries.

Stray dogs and cats can wander over large distances. Unless the animal carries some permanent identification; it is unlikely that anyone finding it will be able to contact the owners or know how to reunite them. Animal shelters have limited room, and unless the owners come forward within a certain period of time, the animal will likely be given a new home or even eventually be put to sleep. The information stored on a microchip implant is held on a central database allowing owners to be quickly contacted. This saves time and distress for the owners and their pets, cuts down the numbers of strays in shelters, and saves money for the organizations which look after them. Additionally, a registered microchip may help determine who owns a particular animal should an ownership dispute arise.

A microchip is a small implant, about the size of a grain of rice, that contains a unique multidigit code. The code number is registered on a national microchip database and should also be noted down on your pet’s vaccination record, passport, and/or Animal Health Certificate. The chip is made of an inert (non-reactive) material which means it has no power source and won’t be rejected by your pet’s body. To retrieve your pet’s identification number, a scanner is passed over its body. The scanner sends out a magnetic field that picks up the numerical code imprinted on the chip and the code then appears on the screen of the device. The person scanning the pet can then contact the microchip database and provide the code. The database providers can then notify the owner about discovering their animal via the registered contact details. Veterinarians, police, rescue centers, and dog wardens will all have microchip scanners.

Microchips are injected under the skin at the base (scruff) of the neck with a wide-bore, sterile needle. Once your veterinarian or other qualified person has implanted the chip, it should remain in this location. However, it is not uncommon for them to move around a little under the skin, and so when an animal is scanned, it is usual practice to scan the whole body, not just the scruff.

As the code is permanently embedded on the chip, there is no risk of the code being tampered with or changed. Just as importantly, the code gives more than enough capacity for every pet animal in the world to be given its unique number. It is unlikely, but If the microchip fails, and the identification number is unreadable by a scanner, your veterinarian may need to insert a new one. The registration for both these chips should then be maintained in case the original chip is picked up on a future scan.

There is some international agreement on microchip standards so that microchips implanted in one country should be readable in others. Where possible, ISO (International Standards Organization) compliant microchips should be used. If you are planning to take your pet abroad, you should inquire about the type of microchip being implanted in your pet. Compatibility between chips and readers may be an issue if your pet has been microchipped abroad. If the microchip does not conform to ISO standards, it may not be able to be read by a standard microchip reader when the animal is checked at the time of travel. If your pet does not have an ISO microchip, you should discuss this with your veterinarian. ISO chips are required for entry into many countries (particularly Europe).

Pets should be fitted with a collar and address tag, although collars can easily be removed or become lost, as well as tags becoming damaged. For many years tattoos have also been used to identify an animal permanently. Still, this method has several disadvantages: the ink can fade and become unreadable, the animal must be given a general anesthetic to keep it still when applying the tattoo, and tattoos can also be altered by further tattooing. There is also a risk of errors when writing down any long number, and it may be difficult to print a long code on the skin of smaller animals. Pets traveling abroad may use tattoo identification instead of a microchip, provided the pet was tattooed before 3rd July 2011, the tattoo is legible, and the pet was vaccinated against rabies after the tattoo was placed. A veterinarian must note this information in the pet’s passport and/or Animal Health Certificate as appropriate.

Microchips should only be implanted by a veterinarian or suitably trained person as injuries can occur due to poor implantation.

The microchip is implanted into the animal’s scruff while they are awake. Although the needle is a little larger than the type used for your pet’s vaccinations, most animals tolerate the process very well. If your pet is very sensitive or nervous then discuss this with your veterinarian beforehand and they can consider the best option for your pet. Implantation is quick and takes about the same amount of time as any other injection. Occasionally the insertion site may ooze a few drops of blood after insertion. The chip is sterile, so although there is always a very slight risk of introducing infection, as with any injection, this risk is very small. Rarely, the chip can move under the skin away from the original site, but as long as the chip stays intact, it can be read anywhere in your pet’s body. To date, there is no strong evidence between tumor formation and microchips, despite media speculation. Discuss any concerns you have with your veterinarian.

Once the microchip has been implanted and the owner details registered, the animal is permanently listed on a microchip database. Many microchip providers pre-register their chips to one database provider. Even if an owner does not register their details, the company selling the chips might be able to trace the location of where the chip was implanted. These database companies will maintain contact details and registration information for other microchip database providers, so registration with multiple companies is unnecessary.

When an animal is found, its microchip is read with the scanner, and the number is checked on the database. This provides information on the owner, who can then be contacted and informed of their pet’s whereabouts. Owners must keep information up to date on the database in the event of moving home or changing phone numbers. The microchip will be ineffective without the correct owner’s contact details. A very common problem with stray dogs brought to veterinarians or dog shelters is that they are microchipped, but the contact details are out of date, and so although it is known that the dog is owned and loved, it is difficult to reunite them.

Using a “pet door” to allow the pet free access to the yard is helpful for some owners. Pet doors are available with sensors that can be programmed to recognize one or more individual pet microchips to allow only these pets access to the house while preventing other animals from entering. Feeding stations with microchip readers are also available. The feeder has a cover that can be programmed to open only for the pet with the registered microchip. This can be useful for multi-pet households to prevent overfeeding or make it easier when one pet in the household needs a prescription diet or medication in its food to which other pets should not have access. Some microchips can give information about the animal’s body temperature, if read with a compatible scanner.

Pet owners should however remember that microchips are not GPS trackers. They cannot track or give the location of your pet if they become lost.