Good point. But the hedgehog is a nocturnal animal, so it won’t apply to him. However, it is also a hibernating animal, and such are rather good at predicting when Spring will arrive: after all, their lives may depend on their being right.
Agreed.
However, using the aspect of the Groundhog being still in hibernation or not is not the test being applied. For that, the test should be humans looking into his den and checking his respiration rate, pulse, etc.
With the in-practice test being whether the animal itself casts a shadow, as observed by humans, I think I’ll go by my original clear/dry/cold versus cloudy/stormy/warming test, where no actual hedgehog need be involved.