Skin is visible under the fur

Question
Hello tamarah! On my mouse there appears to be a hole on its back.  I can see straight to the skin.  It appears healthy and is walking around but i have never seen this before.  Gregory ( the mouse) shares this cage with frederick they never fight and i take good care f them.  Im just wondering if this is a HOLE or it is just the way the fur is?

Answer
Hi John,

If you can see the skin, and the skin itself looks healthy, then it's just a gap in the fur.  This could have been caused by a bite, so if you can, you should ruffle the fur around in the area and see if there's any little mark hiding in it.  If there is, you should disinfect it (with betadine diluted with water to the color of tea - you can find this at your general store or in a pharmacy) and consider separating them - you might just not be around when they fight.  Males can sometimes get along, but a bite may be your first sign of trouble, and things can go south quickly between boy mice.  If it's not a bite, it could be another injury, like a scratch from Frederick or something sharp in the cage (sometimes they can chew on things in their cage and create points where there weren't originally).  It could also be a bug bite - but in any case irritation or an injury would have to be visible to figure out what caused it.

If you can't find any broken skin or swelling, and the skin looks normal, I would wait to see if the fur grows back or if fur loss spreads.  A hole in the fur itself isn't a problem - the only thing that's important to look for is injuries under the coat or other signs of fighting.  If you do separate the two, be *very* careful about re-introducing them and consider keeping them separate permanently, because males do have a reputation of not getting along well, and do not need a cagemate to be happy.

Best of luck!
-Tam