Absolutely genetic, in this case a recessive (hypo-melanistic) gene caused a lack of dark pigment. It remains recessive because natural selection tends to kill it off as it occurs. Same thing with 'melanistic' animals, the excessive dark pigment also makes them stand out from the crowd and increases mortality rates.My guess is genetic.
Absolutely genetic, in this case a recessive (hypo-melanistic) gene caused a lack of dark pigment.