Found a white mouse

Question
I found a small white mouse in my garage today. It managed to get into a garbage can, so I took it outside and let it go. I didn't want to hurt it. I have never seen a white mouse outside a pet store before, but I did have a small brown mouse make it's home in my garage earlier in the year. It too, fell into my trash can, so again, I took him out and freed him. I live outside the city, so frequently, I have snakes and squirrels in my yard, but never a tiny white mouse. So, my question is: Is it unusual to see a white mouse outside like this? Oh, and was I supposed to let it go or capture it and take it to a pet store?  Thanks!

Answer
Dear Linda,

Yes.  Incredibly rare. I don't know your living situation, but if you live in an apartment complex or somewhere else with adjacent neighbors, the mouse was probably someone's pet.  If not, it was an albino.  Albino animals are all white because (roughly) they have a genetic defect that makes them have no pigment in their fur, eyes, etc.  Although it is genetic and passed from one generation to the next, it is very rare because, well, assume an owl is looking for dinner in a dark field with 99 brown mice and one white one. Which one will be dinner?!  Being seen means poor survival for both prey and predators.  Thus, the genes for albinism are carried by parents which are not albino.  It only happens when both parents carry one hidden albino gene.  

White mice on the other hand are very common-- as pets.  This is (again, roughly) because the rare white mice were the ones people found amusing back when people started breeding mice for pets over 2000 years ago.  In fact, white mice were worshipped in at least one part of ancient Egypt because they were thought to protect the grain from the rest of the mice.  There were temples to white mice, and the mice were bred in captivity.  In Japan as well, white mice were bred for their amusing appeal.  Other genetically defective mice were bred as well-- for instance, there are 'waltzing' mice, which go around in circles because the poor things have an inner ear imbalance-- but as opposed to that sort of defect, albinism carries no disadvantages other than visibility, and so they are easy to breed and keep.

I don't know if modern scientists traditionally use white mice simply because that's what you could buy back at some point, or if they began to be the typical scientific lab model because they are the perfect study of recessive genes, or why, but these albino mice are the ones that made it into pet stores whenever pet stores started carrying mice.  These days you can get all kinds of colored mice at pet stores, but some people still call them "white mice" as opposed to wild ones.  You can also get actual white mice today without the red eyes of an albino, and colored mice with red eyes, but that wasn't the case when I was a kid.  That's from very deliberate genetic manipulation.

To make a long story short, yeah, you should have kept the little critter to at least have a vet examine it and figure out what its story was.  A pet store couldn't have put it in with their mice because it would undoubtedly have diseases or parasites from the wild that would endanger the rest of the mice.  Because as I stated above, albinism has to be carried by both parents, it is unlikely that your mouse was a even second generation from someone's lost pet, unless siblings of a white-wild mouse pair mated.  I really wonder.  Ah well, next time!

squeaks n giggles,

Natasha