vultures don’t have feathers or hair on their heads because all that rotten meat from dead animals could make them sick if it is stuck in their head feathers.
Is fairness determine by skin color or the relative size and shape of facial features or the shape of the female based on the relatively large size of a baby at birth? All are subjective and usually are influenced by time, place, and association.
How can you tell through the glass whether she is in heat? That is what matters to a dog!