Re: hole in ear & scabs on back

The average life span of a mouse is 1 to 3 years so maybe your mouse is
getting older & more prone to the diseases of aging but it could also
be mites. I had the same thing happen to my mouse (but he sratched off
his whole outer ear)  and it was mites which are very hard to see
without magnification. They look like little black spiders. You can get
rid of mites with Ivermectin which you can buy at a farm supply store.
It costs about $10-$15 for a tube of it. You only need to apply an
amount about the size of a grain of rice on the back of each ear.  Do a
word search in this group on both the words 'mites' & also
'ivermectin'. Do it ASAP or your mouse's condition will get worse.
Mark