The least adaptive feature of arboreal life is shading of coat colour.
Arboreal animals are animals that live primarily in trees, and they have evolved many adaptations that allow them to live and move effectively in this environment. For example, possession of four limbs and claws are adaptations that help arboreal animals to grip onto branches and climb trees. Development of a long tail is another adaptation that helps with balance and maneuvering in trees.
However, shading of coat colour is not an adaptive feature for arboreal life. While some arboreal animals may have developed specific coat colours to help them blend in with their surroundings and avoid predators, this is not a universal adaptation for all arboreal animals. In fact, some arboreal animals have bright or distinctive colours to help them attract mates or communicate with other members of their species.
Therefore, the correct answer is "shading of coat colour" as it is the least adaptive feature of arboreal life compared to the other options given.