Part 2: Surprising variation in the chestnut in various subspecies of the plains zebra

@michalsloviak @tonyrebelo @alanhorstmann @maxallen @colin25 @chewitt1 @johnnybirder @jwidness @jakob @jeremygilmore @mgargiulo

...continued from https://www.inaturalist.org/posts/68122-interspecific-variation-in-the-form-of-the-chestnut-among-equids-part-1#

As far as I know, nobody has previously examined the chestnut (https://en.wikipedia.org/wiki/Chestnut_(horse_anatomy)) in the plains zebra (Equus quagga).

The chestnut seems to vary in two different ways within this species.

Firstly, it varies in size, with the chestnut of Equus quagga crawshayi tending to be anomalously small (albeit with individual variation).

Secondly, it varies in the degree to which it is obscured by the striping on the upper foreleg.

As a result, the chestnut is

conspicuous in Equus quagga quagga and Equus quagga burchellii,
inconspicuous in Equus quagga crawshayi, because the chestnut tends to be both small and obscured by striping,
inconspicuous in Equus quagga borensis, because the chestnut is as large as in most subspecies, but obscured by striping, and
of intermediate conspicuousness in Equus quagga chapmani and Equus quagga boehmi, because the upper foreleg is striped but not around the chestnut.

In E. q. quagga and E. q. burchellii, the chestnut is

as conspicuous as in any member of the genus Equus, and
similar in appearance to those in Asian wild asses (Equus hemionus, Equus kiang, and Equus khur, http://www.kimballstock.com/pix/MAM/14/MAM-14-KH0288-01P.JPG ).

In E. q. crawshayi and E. q. borensis, the chestnut is almost as inconspicuous as in Equus zebra (https://www.shutterstock.com/image-photo/cape-mountain-zebra-equus-national-park-1282130179), Equus hartmannae (https://fossilrimblog.files.wordpress.com/2014/04/rs2686_12-5.jpg), and Equus grevyi (https://www.alamy.com/full-body-side-view-of-grevy-zebra-walking-in-the-bush-in-samburu-in-kenya-image364435205.html and https://www.alamy.com/stock-photo-grevys-zebra-equus-grevyi-122867476.html?imageid=30B3BEAA-C495-4E68-8C91-71131C44329B&p=354315&pn=2&searchId=4dda47820ae27bc9059f9c91451c28a7&searchtype=0).

The two northernmost subspecies, E. q. boehmi of the Serengeti, and E. q. borensis of the borders of Kenya with Uganda, Sudan, and Ethiopia, have similar striping. Their main difference is the tendency to manelessness in E. q. borensis. It is therefore somewhat surprising that the chestnut is usually obscured by the relatively bold striping in E. q. borensis (https://www.flickr.com/photos/j-l-t-photography/29554465761), to an extent not usually seen in E. q. boehmi (https://zooinstitutes.com/animals/grants-zebra-wildlands-adventure-zoo-emmen-37259.html).

Perhaps the biggest surprise is that, in at least some individuals of E. q. crawshayi, the chestnut is hardly visible (https://www.alamy.com/crawshays-zebra-in-south-luangwa-national-park-zambia-image357741827.html).

QUAGGA

The chestnut is conspicuous, partly because the forelegs are whitish and lack striping.

http://www.mwnh.de/imag/mus085.jpg
https://www.extinctanimals.org/wp-content/uploads/2015/07/Quagga-Zebra.jpg
Scroll to Wiesbaden specimen in http://breedingback.blogspot.com/2013/10/normal-0-21-false-false-false-de-ja-x_31.html

The following painting of the extinct quagga, reputedly made using a real captive specimen as model, confirms a conspicuous chestnut owing to fairly large size and dark tone.

http://2.bp.blogspot.com/-_8FOLNDog6E/Tz2GJSGhhVI/AAAAAAAAA3E/esBJs37QxwE/s1600/723px-Agasse_Quagga.jpg

BURCHELLII

https://www.timbrowntours.com/wp-content/uploads/2014/06/Zebra-crossing-road-on-our-Durban-Big-5-Private-Day-Safari-Tour-to-Hluhluwe-Umfolozi-Big-5-Game-reserve-28th-June-2014.jpg
https://www.dreamstime.com/royalty-free-stock-photos-burchell-zebra-side-profile-portrait-image25158388
https://www.alamy.com/zebra-at-etosha-national-park-namibia-image465034743.html?imageid=F50C35B3-6037-46D3-BC99-8F2FC8EF1477&p=310546&pn=2&searchId=4dda47820ae27bc9059f9c91451c28a7&searchtype=0
https://www.shutterstock.com/image-photo/plains-zebra-common-equus-quagga-formerly-1681478740
http://thumb9.shutterstock.com/display_pic_with_logo/1215434/190604102/stock-photo-burchells-zebra-walking-190604102.jpg
https://www.robertharding.com/preview/743-601/burchells-zebra-foal-equus-burchelli-redbilled-oxpeckers-buphagus/

CHAPMANI

https://www.istockphoto.com/photo/zebra-portrait-gm489981636-74972167
https://www.bigstockphoto.com/image-416280568/stock-photo-common-zebra-%28equus-quagga%29-walking-in-green-savanna-in-kruger-national-park-south-africa
https://www.alamy.com/adult-zebra-with-muddy-hooves-walking-near-a-waterhole-in-kruger-park-in-south-africa-image370697264.html?imageid=D3F2C754-B599-4A7B-BEE7-234897F618BB&p=4830&pn=1&searchId=a66e4b9a64c576eb6a53858abf65ed24&searchtype=0
https://www.alamy.com/three-zebras-walking-in-staggered-tandem-image220478276.html?imageid=1D3CF339-2340-4E8D-A93A-EEFF5A1C8342&p=365196&pn=2&searchId=4dda47820ae27bc9059f9c91451c28a7&searchtype=0
https://www.shutterstock.com/image-photo/small-zebra-foal-standing-oxpecker-on-278165210
http://thumbs.dreamstime.com/x/1233293http://www.dreamstime.com/stock-photos-zebras-profile-one-bendin-1233293.jpg

CRAWSHAYI

https://www.naturepl.com/stock-photo-crawshay-39-s-zebra-equus-quagga-crawshayi-eating-a-fruit-sausage-nature-image01644679.html
http://www.africaimagelibrary.com/media/f8641cf6-4696-4271-8792-38febc5e91ee-crawshay-s-zebra-equus-quagga-crawshayi-south-luangwa-natinal
https://travelswithben.com/2018/07/18/zebras-at-south-luangwa-national-park-zambia/
https://www.alamy.com/stock-photo-crawshays-zebra-foal-equus-quagga-crawshayi-south-luangwa-national-86003548.html
https://www.alamy.com/stock-photo-crawshays-zebra-equus-quagga-crawshayi-adult-standing-on-grassland-70270064.html
https://www.alamy.com/stock-photo-crawshay-zebra-equus-quagga-crawshaii-south-luangwa-national-park-88590529.html
https://www.alamy.com/chapmans-zebra-equus-quagga-chapmani-standing-on-the-dry-arid-empty-savannah-in-south-luangwa-national-park-zambia-image369897300.html?imageid=0C5C1FA5-2CC5-490E-BB64-BDCD30342B78&p=364701&pn=13&searchId=23ce11cb0d23a1b3922b090004c28a43&searchtype=0
https://www.alamy.com/stock-photo-crawshaw-zebra-south-luangwa-national-park-zambia-12150521.html?imageid=86CE7F1D-3DE8-4BA3-B765-5D8C38CF8743&p=33444&pn=1&searchId=c1ba876f280b14f5c4ef1c76cfd026ee&searchtype=0
https://www.alamy.com/crawshays-zebras-equus-quagga-crawshayi-in-south-luangwa-national-park-in-eastern-zambia-image344311950.html
https://www.alamy.com/stock-photo-crawshays-zebra-equine-grazer-herbivore-plains-zebra-subspecies-south-33136534.html
http://www.photo-thierry-riols.com/galleries/images_slider/zebre-de-crawshay-luangwa-zambie_d4a6611-1268.jpg
http://c8.alamy.com/comp/E29254/crawshays-zebra-equus-quagga-crawshayi-adult-standing-on-grassland-E29254.jpg
http://cdn26.us1.fansshare.com/photo/nyikaplateaunationalpark/zebra-wildlife-malawian-style-malawi-national-parks-reserves-nyika-national-park-nyika-plateau-national-park-2065319918.jpg
https://vijilworldtour.files.wordpress.com/2015/06/dscn4477.jpg
https://www.alamy.com/crawshays-zebras-equus-quagga-crawshayi-face-to-face-south-luangwa-national-park-zambia-image229348460.html
Scroll in https://adventuresoflilnicki.com/south-luangwa-national-park-zambia/
https://www.alamy.com/zebras-in-south-luangwa-park-mfuwe-zambia-image264492274.html
https://www.canstockphoto.com/trio-of-zebra-4842521.html
https://www.flickr.com/photos/149768393@N06/47155200411/
https://www.alamy.com/crawshays-zebra-in-south-luangwa-national-park-zambia-image357741579.html
https://pixels.com/featured/zebras-south-luangwa-david-stribbling.html?product=puzzle&puzzleType=puzzle-18-24