[logbiscuitswave]

The microchips are basically little RFID widgets that are about the size of a grain of rice. The chip can migrate from between the shoulder blades to anywhere else, and the range is really poor - basically near-contact range.

I once tried a pet feeder that would read a cat’s microchip to determine if it would allow that cat to use it. It worked by having an arch with an RFID sensor that the cat would pass under and it would uncover the food for the matching cat. For one of my cats, it worked great because the chip was still between her shoulder blades in the usual spot. For my other cat it had migrated near her ribs and it didn’t work at all.