HAd some mold develop on an elk last year. First time I've experienced it.
I attribute it to hanging in an uncontrolled environment (garage) for close to 2 weeks. Fluctuating temps may have been the cause. Have had moose hang for over 2 weeks in a cooler and not a spot of mold.
We had left the hide on the elk. Mold on the inside of the cavity.
It ended up being fine eating and still alive today