When an animal has a dark-coloured dorsal surface and a light-colouration ventral surface, this is an adaptation called
Answer Details
The adaptation described in the question is called countershading. Countershading is a form of camouflage in which the upper part of an animal's body is darkly colored while the lower part is light-colored. This adaptation helps to conceal the animal from predators or prey by breaking up its outline and making it more difficult to see. The dark dorsal surface blends in with the dark background above, while the light ventral surface blends in with the brighter background below, making the animal appear more uniform in color and therefore harder to detect.