Do pectoral insignia compensate for small eyes?
(writing in progress)
Pectoral insignia are conspicuous pale patterns on an otherwise dark chest, in some cases extending to the front of the neck. They tend to be irregular and individually variable.
This category of patterns occurs in various unrelated mammals, apparently owing to evolutionary convergence.
Examples include:
- various Carnivora, particularly most spp. of bears and many spp. of mustelids (https://en.wikipedia.org/wiki/Sun_bear#/media/File:Sun-bear.jpg and https://en.wiktionary.org/wiki/sun_bear#/media/File:Sitting_sun_bear.jpg and https://www.americanbear.org/education-awareness/bears-of-the-world/ and https://www.alamy.com/stock-photo-asiatic-black-bear-or-moon-bear-ursus-thibetanus-85475078.html and https://animalia.bio/giant-otter and https://www.shutterstock.com/de/image-photo/giant-otter-open-mouth-water-front-2102150371 and https://www.inaturalist.org/observations/47238087 and https://www.inaturalist.org/observations/27838866 and https://www.researchgate.net/figure/Wolverine-Gulo-gulo-Photo-Kjetil-Schjolberg-Rovdata_fig1_293800942 and https://www.superstock.com/asset/north-american-wolverine-gulo-gulo-luscus-captive-animal-game-farm/4141-34263),
- porcupines, Hystrix (https://www.wallsheaven.com/wall-murals/indian-crested-porcupine-hystrix-indica-couple-caring-for-each-other-E366205781 and https://stock.adobe.com/search?k=%22cape+porcupine%22&asset_id=398680985 and https://africafreak.com/porcupine-facts and https://stock.adobe.com/search?k=%22cape+porcupine%22&asset_id=247580434 and https://www.wallsheaven.com/wall-murals/an-african-crested-porcupine,-hystrix-cristata-C22332055 and https://www.wallsheaven.com/wall-murals/malayan-porcupine,-himalayan-porcupine,-large-porcupine-D836813326 and https://www.wallsheaven.com/wall-murals/stachelschweinchen-C36893152 and https://www.wallsheaven.com/wall-murals/stachelschwein-A052949122 and https://www.wallsheaven.com/wall-murals/porcupine-is-isolated-on-a-white-D431165186),
- a marsupial, Sarcophilus (https://www.bbc.com/news/world-australia-57558396 and https://scitechdaily.com/tracing-back-through-time-the-secret-life-of-tasmanian-devils-is-hiding-in-their-whiskers/ and https://www.theweek.in/news/world/2021/05/27/first-tasmanian-devil-joeys-born-on-mainland-australia-in-3-000-.html and https://www.kktv.com/2021/05/31/tasmanian-devils-born-on-australian-mainland-for-first-time-in-3000-years/ and https://www.freepik.com/free-photo/tasmanian-devil-sarcophilus-harrisii_15252845.htm#query=tasmanian%20devils&position=27&from_view=keyword#position=27&query=tasmanian%20devils), and
- a few species of bovin/tragelaphin ruminants (https://www.inaturalist.org/taxa/524158-Tragelaphus-scriptus-sylvaticus and https://www.ingwelala.co.za/archives/fauna-flora/bushbuck.html and https://nickbowkerhunting.com/plains-game/bushbuck-hunting.php and https://twitter.com/SabiSabiReserve/status/1042645656115052544 and https://www.istockphoto.com/photo/male-sitatunga-antelope-gm179262405-25492095 and https://africageographic.com/stories/sitatunga/).
At first sight, this array of mammals is so diverse that it seems unlikely that we would find much in common among them.
However, there may be at least one consistent theme: they tend to combine relatively small eyes with mainly nocturnal activity, or diurnal activity in forests with dim illumination.
If the relatively small eyes indicate poor vision compared with felids, canids, viverrids, hyaenids, herpestids and euplerids, the one can imagine an adaptive function for clear pale markings signifying identity for social purposes..
Most of the species in question seem to rely on olfaction as much as on eyesight.
The genus Anoa consists of a miniaturised water buffaloes, restricted to the island of Sulawesi. Anoas have small eyes for bovids, which is sufficient partly because their island habitat is relatively free from indigenous predators.
The following show various details of Anoa:
http://static.zoonar.com/img/www_repository1/34/43/3f/10_2eeb9578f8f4eb6a0bcca166cc377695.jpg
http://www.biolib.cz/IMG/GAL/182564.jpg
http://www.theonlinezoo.com/img/13/toz13515l.jpg
http://www.biolib.cz/IMG/GAL/6006.jpg
https://thumbs.dreamstime.com/t/lowland-anoa-22266667.jpg
http://online-zoo.net/wp-content/uploads/2017/02/Anoa-Bubalus-388x220.jpg
https://photos.mongabay.com/10/0202lowland_anoa.jpg
http://www.endangeredearth.com/wp-content/uploads/es_list/lowland_anoa_2.jpg
http://pennyhyde.zenfolio.com/img/s9/v97/p482983823-11.jpg
https://upload.wikimedia.org/wikipedia/commons/thumb/6/64/Lowland_anoa.jpg/220px-Lowland_anoa.jpg
http://www.chesterzoo.org/~/media/images/animals/mammals/hoofed-animals/anoa/anoa-21.jpg?la=en
Anoa is fairly uniformly dark, except for a constellation of pale markings which make little sense in terms of camouflage. These pale punctuations include part of the front-of-ear, the bases of the horns, one spot on the cheek and another on the mandible, an upper and a lower band on the front-of-neck/chest, variable markings on the lower forelegs, and markings on the anterior surface of the fetlocks.
(writing in progress)
Comments
Pseudoryx ngethingensis (https://en.wikipedia.org/wiki/Saola) is small-eyed and presumably nocturnal but seems to bend the 'rules' by having its pale bar on the hindquarters instead of the chest.
Add a Comment