It is a genetic thing. I have many mice that have them. Usually only when I pick them up. They will seiz while I am holding them by their tails. I have not noticed them affecting breeding or anything. But I only handle my mice when I clean the cages.
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Shannon in Reno
1.0 savannah monitor (Pombe-means "beer" in Swahili)
2.4 dogs
1.0 cat
5.32 rats
6.44 mice
7.50 chickens
1.2 beardies
0.1 black rat snake
~500 hissers
1 giant millipede
0.1 Chissel tooth kangaroo rat
1.1 rabbits
1.0 wonderful husband

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