The facial ruff in lynxes as an alternative form of facial flag

The facial ruff, which occurs in two genera and five species of felids, is hard to interpret adaptively.

The facial ruff seems superfluous to camouflage, and risks being conspicuous to prey during stalking. It seems to be a social or sexual adornment, but is unlike the lion's mane because it is present in females as well as males.

The range of forms of the facial ruff within the genus Lynx can be seen in http://justfunfacts.com/interesting-facts-about-lynx/.

Besides lynxes, the facial ruff occurs only in the tiger, and is best-developed in the smallest, Sumatran, subspecies (see https://www.independent.co.uk/voices/comment/save-tiger-7-saddening-facts-about-extinction-javan-tigers-9630717.html).

A key to understanding the facial ruff could be as follows:

in several other species of felids, there is a subtle facial flag consisting of whitish upper lips, lower lips, chin and throat,
this pale region breaks the camouflage pattern enough to gleam conspicuously when the head is held high, and
at the same time this pale region, associated with the mouth, can be hidden by lowering the head, while the eyes maintain a clear view.

What all the felids possessing the facial ruff have in common is that the mouth is as camouflaged as the body, with dark spots/stripes on the upper and lower lips. One of the subtle peculiarities of lynxes is that the lips are camouflaged (see https://www.inaturalist.org/observations/72509038).

The conspicuous region has been transferred to the facial ruff instead. (The Eurasian lynx is something of an 'exception which proves the rule' because its facial ruff is proportionately small, and sure enough its whitish chin is free of spots/stripes: https://depositphotos.com/388877600/stock-photo-lynx-walking-wild-cat-forest.html.)

On this basis I hypothesise that at least one of the functions of the facial ruff is to act as a facial flag for social purposes.

The following show how conspicuously pale the mouth region of the European wild cat (Felis silvestris) can look: https://www.alamy.com/stock-photo-european-wild-cat-felis-silvestris-silvestris-sitting-in-the-snow-139351478.html and https://www.sciencephoto.com/media/972630/view/wild-cat-in-snow.

The following show the same effect for the jungle cat (Felis chaus): https://www.dancingpelican.com/dp_gal/jungle-cat/ and https://www.istockphoto.com/photo/jungle-cat-felis-chaus-portrait-of-adult-gm1257150508-368320158 and https://zooinstitutes.com/animals/jungle-cat-abu-kabir-university-zoo-3459.html and https://www.catsforafrica.co.za/jungle-cat-felis-chaus/ and https://www.agefotostock.com/age/en/details-photo/jungle-cat-felis-chaus-asia-adult/JHS-DS03715.

The following shows - for particular comparison with the tiger - a similar effect in the lion: https://www.canstockphoto.com/female-lion-looking-at-camera-18526434.html.

The following photos are arranged by species, sex and ontogenetic stage of development. They show that lynxes and the tiger conform approximately to a pattern in which the mouth region is inconspicuous (being spotted/striped) but the facial ruff is relatively conspicuous. This is mainly because the facial ruff is pale, but also because it is accentuated with dark markings.

Lynx canadensis adult https://motherturtle.com/blogs/mother-s-blog/posts/lynx-or-bobcat and https://www.bigstockphoto.com/image-168191864/stock-photo-canada-lynx-sitting-on-a-snow-covered-hill-in-a-foresthttps://en.wikipedia.org/wiki/Canada_lynx#/media/File:Canada_lynx_by_Michael_Zahra_(cropped).jpg and https://en.wikipedia.org/wiki/Canada_lynx#/media/File:Canada_lynx_portrait_by_Michael_Zahra.jpg and https://a-z-animals.com/animals/canada-lynx/pictures/

Lynx canadensis 9 months old https://www.123rf.com/photo_9648480_9-month-kitten-of-canadian-lynx.html

Lynx lynx adult https://i.redd.it/r33ypyfwra871.jpg and https://www.123rf.com/photo_48177661_a-close-up-of-the-face-of-a-eurasian-lynx.html and https://www.deviantart.com/sikaris/art/Eurasian-Lynx-001-190143739 and https://www.flickr.com/photos/tambako/14405215724 and https://www.flickr.com/photos/tambako/25873290876

Lynx pardinus adult male https://www.awl-images.com/stock-photo-iberian-lynx-male-lynx-pardinus-in-donana-national-park-with-a-collar-image00400995.html

Lynx pardinus adult female https://pixlr.com/stock/details/1238207344-iberian-lynx-or-lynx-pardinus-at-wild-life-park/

Lynx pardinus adult https://wildcatconservation.org/wild-cats/eurasia/iberian-lynx/ and https://www.express.co.uk/news/nature/909438/Big-Cats-Iberian-lynx-rare-cat-camera-footage and https://www.independent.co.uk/climate-change/news/sixth-mass-species-extinction-human-stop-prevent-colonisation-a8988831.html and https://www.wikiwand.com/en/Iberian_lynx

Lynx rufus https://www.videvo.net/video/nice-closeup-of-a-bobcat-face-in-the-forest/618017/ and https://www.videvo.net/video/lynx-face-zooms-in/507599/ and https://dailybulldog.com/features/teeming-with-life/ and https://www.dreamstime.com/royalty-free-stock-photography-lynx-bobcat-close-up-image13677797 and https://www.cattales.org/store/p41/Stitches_-Bobcat-_Adoption.html

Panthera tigris sondaica adult female and male together https://www.alamy.com/male-and-female-sumatran-tigers-panthera-tigris-sumatrae-captive-native-to-sumatra-indonesia-image262995359.html

Panthera tigris sondaica adult female https://www.flickr.com/photos/pg-photography/1531399476 and https://www.shutterstock.com/image-photo/female-sumatran-tiger-daseep-looking-over-1594901932

Panthera tigris sondaica adult male https://photos.com/featured/male-sumatran-tiger-picture-by-tambako-the-jaguar.html and https://www.alamy.com/stock-photo-a-male-sumatran-tiger-panthera-tigris-sumatrae-from-the-wildlife-heritage-16989262.html and https://fineartamerica.com/featured/one-eyed-male-sumatran-tiger-at-edinburgh-zoo-colin-mackay.html and https://www.walesonline.co.uk/news/wales-news/two-year-old-sumatran-tiger-11207722

Panthera tigris sondaica https://www.nationalgeographic.org/photo/tiger-sumatran/ and https://www.flickr.com/photos/jimnicholson/4702268669 and https://www.alamy.com/sumatran-tiger-image275690192.html and https://www.dreamstime.com/sumatran-tiger-close-up-its-beauafull-face-image175570371 and https://www.istockphoto.com/photo/sumatran-tiger-face-gm955854152-260973083

Lynx canadensis infants and juveniles https://en.wikipedia.org/wiki/Canada_lynx#/media/File:Canada_Lynx_Mom_and_Kitten_(15250932421).jpg and https://photos.com/featured/canada-lynx-kitten-mark-newman.html and https://pixels.com/featured/canadian-lynx-kittens-thomas-and-pat-leeson.html and https://numpaint.com/products/canadian-lynx-kitten-new-paint-by-numbers/