I had wondered about migration when chips first came out. A few years forward, I was told the chip companies addressed that issue and designed the chip with indentations on it... which in theory , I guess the fatty tissue would grow into the notches and therefore anchor the chip.
I have a scanner and I've checked chip locations on my dogs throughout the years, just to see if they had moved at all. I have not seen any that moved substantially.
As far as cancer at the implant site... I've had over 150 rescue dogs micro-chipped and all of my own dogs. Not one of those dogs developed any problems at the microchip site.
Everything in life has pros and cons.
Based on my experiences with microchips, I think the benefit of the chip outweighs the risks. So I chip my animals.
The beauty is that we live in a free country where we can make our minds up and have personal choice.
As far as the dog with 2 chips -- I had considered asking my vet if he could surgically remove the shelter chip when I take him in for a dental and some growth removals.
I appreciate Dr Doug's comments on this. I don't want to put the dog through any undue pain or risk.
What kind of worries me is that IF he were to ever get lost, if he is scanned - once a shelter picks up a chip number they are going to stop scanning. And I have no way of knowing which chip will read.
I've tried scanning him several times. With the scanner against the skin and moving very slowly, it appears that one chip is on his left side and the other on the right side.
But.... if I hold the scanner 2 inches above his body and scan -- it will pick up a chip number -- but it's not consistent - it reads either chip from that distance with no rhyme or reason to it.
I don't know why the shelter would have double chipped him. The microchip companies have provided free scanners to shelters and rescues in the past -- the shelter has to agree to scan every dog coming in, and again before they are adopted or euthanized. If he was scanned, why would they double chip? I'm thinking no one bothered to scan him.... but who knows.
And if this is the biggest problem I have, I am pretty well off. :B