Apparently, does that don't/can't have fawns, have this coloring.
It's been explained to us as the extra fat layer that they put on because they don't lose weight like does who get pregnant, feed babies, etc. It's said that it's that extra fat layer that makes them appear more blue in hue.
I'm not sure if that's the correct reason, or not, but in 32 years we've never seen a blue doe with a baby, and they are always much more filled out, weight-wise, than the other does.
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