Ocular displays in macaques (Macaca), part 2: Japanese macaque (Macaca fuscata) and Sulawesi macaques (Macaca spp.)

...continued from https://www.inaturalist.org/journal/milewski/98203-ocular-displays-in-macaques-macaca-part-1-semets-small-scale-patterns-of-conspicuous-colouration-about-the-eyes-in-the-southern-pig-tailed-macaque-macaca-nemestrina#

The main ocular display in Macaca fuscata, as in M. nemestrina, is one that accentuates the stare (https://www.alamy.com/japanese-macaque-snow-monkey-close-up-of-face-nagano-japan-image3327912.html). The relevant colouration is the darkness of the sclera immediately adjacent to the iris, which emboldens the whole eye (https://commons.wikimedia.org/wiki/File:Wildlife_primate_monkey-of-japan_macaca-fuscata_closeup_31-05-2010.jpg and https://www.dreamstime.com/stock-images-face-japanese-macaque-macaca-fuscata-image32246044).

In M. fuscata, an ocular display is weakly-developed, and possibly absent in adults. The eyelids are pale, particularly in juveniles. The sclera, adjacent to the iris, is certainly dark-pigmented, so that in normal views the pale sclera is negligibly visible. This is so particularly because the pterygium (https://www.youtube.com/watch?v=eud5AurOxm0) can be large and darkish, narrowing the visible part of the sclera.

However, in both juveniles and adults, there is in fact a vivid display of the white sclera when the animal glances sideways (https://depositphotos.com/photo/japanese-macaque-face-160912740.html and https://www.flickr.com/photos/serad/4363718078/ and https://depositphotos.com/photo/japanese-macaque-face-160912742.html). This applies to glancing looks to either the left or the right.

Such sideways glances are infrequent. However, the display may be significant. It is as if a 'shifty look' is accentuated, in the ocular colouration of M. fuscata, by a white flash of the sclera that is all the more obvious for being offset by the dark band between the white part of the sclera and the iris itself.

The iris of M. fuscata, like the facial bare skin, is