Microchips are inert and don’t move themselves. The body appears to be able to move them as muscles and fibrous connective tissues move across each other, and move within the body, fat levels change etc.
Combine this more adult movement with the puppy (especially!) microchipped at under 8 weeks when its skin is actually often big enough to hold a 12 wk old!
Implanters do their best to place the microchip in the ‘pocket’ between the shoulder blades which is the recommended place, in an adult lean animal this is easy - in a puppy it certainly isn’t!
The shoulder blades are thought (!) to keep the chip in place, if placed too high up the neck in the common position used by vets for injections then the microchip can migrate across the shoulder to the leg or chest area. If too far back and not within the pocket between the should blades the microchip can move around to the belly or even a rear leg.
Microchip manufactures have their own means of trying to make the microchip stay in place. Some use polypropylene encased microchips or ones with so-called anti migration caps made of parylene. The theory is that these can cause a small reaction to encourage the body to hang onto them. Some (such as Trovan) use medical grade bioglass because it is inert and specifically doesn’t cause a reaction with tissues, which is a concern in some species such as cats in particular.
Whatever method is chosen a small percentage of microchips seem to migrate, its a fact of microchip life.
The major factor is initially placement, but it seems likely that some dogs and their tissues are better at moving chips than others. For those who want to see migration in action we recommend looking on youtube at starfish microchipping, starfish move chips around an expel them through the top of an arm.
Migration is not a big problem:
- If you know where the chip is located then periodically scanning it is worthwhile
- If your dog is lost then it ‘should’ have a full body scan to find any microchips BUT this may be variable. So if your dog is a high risk roamer especially we suggest a second microchip be placed very carefully in the prop[er place. It should be monitored.
- Microchips which end up under the skin are no risk to the dog but may be cracked and damaged and could then stop working. These should be monitored and replaced as above. They are no more prone to infection nor anything else.
In short the procedure itself can NEVER be foolproof, mistakes can be made but the variable of the dog at time and its life can alter things dramatically. Its nobody's fault.