I can see why a cheetah has spots-it helps camoflage him from the eyes of predators. Tigers likewise-the stripe blend in well with the scenery they inhabit. But why does my English Springer Spaniel have his glorious spots? Also, many animals have faces with the “mask” coloration-that is, the eyes are surrounded by darker fur, with a light color between the eyes and covering the muzzle. Raccons and ground squirrels have this-is this pattern of coloration of any advantage to the animal?
Of course, your spaniel is a domestic animal whose coat color has been selectively bred for by humans. It doesn’t necessarily have any adaptive value in nature. Wolves, domestic dogs’ ancestors, have solid coat colors.
Regarding “masks,” they are probably to keep the dark eye from standing out in an otherwise camouflaged animal. A round dark eye on a lighter background can be very easy to pick out. The mask also serves to break up the outline of the head.
There are a number of factors that could potentially render dark pigmentation aroound the eyes beneficial evn if the rest of the aniamls isn’t dark. Masking around the eyes of animals makes it very hard for either predators or prey to know whether an animal is watching by disguising which way the eyeball is facing, thus making it more difficult for them to time their attack/flight. This could be very important for animals that slak small prey like raccoons.
Facial colouration in animals often plays a valuable role in social interaction. It’s a lot easier for other animals to read facial expressions from a distance if the relevant parts of the face are contrasted. This also applies to other body parts, which is one reason why many animals have differently coloured ‘points’ such as the feet, tail tips and ears.
Masking could also serve to stop reflected light from blinding an animal at night. Soldiers and sportspeople playing under lights often use greasepaint to mask their own faces for this reason.
Cancers of the eylids and eyes are a serious problem for animals because their is no hair to cut down UV light. Animals with dark pigmentation around the eyes have an obvious advantage, and such pigmentation usually also means that the eyeball itself is pigmented. Many of the European breeds of cattle which were bred into white or white faced forms have experienced problems with eye cancer due to being reintroduced to the tropics, whereas the pigmented breeds don’t seeem to suffer from the problem. In an attempt to cure the condition many of these breeds have been specifically bred from a white faced form to form with a brown or black mask.
Dappled coats on say, deer, make it easier for them to blend in and hide in amongst dappled shade under partial tree cover.
Dappled coats on say, leopards, make it easier for them to lurk unnoticed in the same places.
It’s an arms race.