American Fancy Rat & Mouse Association

This article is from the WSSF 2017 AFRMA Rat & Mouse Tales news-magazine.

Colors & Coats

Hairless Mice Grow Hair

By Karen Robbins

The mouse in question

Antoine Abed, OH, Facebook
Q Three or four days ago I went into a pet shop and they had baby hairless mice. I bought two of them but they’re growing fur. The boy is a silver gray color with red eyes and has almost all his fur and the girl is black with black eyes and is growing it back. When I got them they were completely hairless except for tiny patches on their ankles. I was really excited for hairless mice. Do you know what is going on?

A Do you know how old they are? In the photo it looks very small and looks like a Lilac (P.E. Black). Did you see the parents? If it is not Hairless, it could be the fz gene (Frizzled/Fuzzy/Fuzzy Hairless) where they have a very short curly coat and some can look almost hairless. The Finnmouse site has a page with several photos of different ones. Or they had something wrong that made them lose their hair and they are now getting their normal coat back in. Normal Hairless shouldn’t have patches left on their ankles when they are through molting which only takes a few days from start to finish. The article The Role of the Hairless (hr) Gene in the Regulation of Hair Follicle Catagen Transformation has a great photo and diagram showing daily hair loss progression. You can see more photos of hair loss on Hairless mice on Christina Beckerman’s Flickr pages (16–18 days) and (18–20 days). Plus she has many other photos of Hairless at different ages along with some photos of fuzzy hairless. *

14-day-old Agouti Hairless male mouse
A 14-day-old Agouti Hairless male mouse just starting to lose the hair around his eyes, owned and bred by Kelli Boka, Lots O’ Spots. Photo ©2008 Karen Robbins.
15-day-old Agouti Hairless female mouse
A 15-day-old Agouti Hairless female mouse. In one day they go from just losing hair around the eyes, to the whole face bare. Mouse owned and bred by Kelli Boka, Lots O’ Spots. Photo ©2008 Kelli Boka.
21-day-old Agouti Hairless female mouse
The Agouti Hairless female at 21 days old with no hair except for whiskers (they do not have ankle tufts of hair). Photo ©2008 Kelli Boka.
21-day-old Agouti Hairless male mouse
The Agouti Hairless male at 23 days now completely Hairless except for whiskers. The ears do straighten out. Mouse owned and bred by Kelli Boka, Lots O’ Spots. Photo ©2008 Craig Robbins.
Agouti Hairless female mouse
One of Kelli Boka’s little bit older Agouti Hairless female mice with unfolded ears. Photo ©2008 Karen Robbins.

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Updated March 22, 2022