Beneficially bloodshot, from birds to buffaloes

@tonyrebelo @koenbetjes @jeremygilmore @ludwig_muller @paradoxornithidae @capracornelius @tandala @oviscanadensis_connerties @maxallen @beartracker @davidbygott @chewitt1 @matthewinabinett @botswanabugs @colin25

As everyone knows, reddish hues in feathers or fur of birds and mammals are usually owing to pigments such as carotenoids (e.g. see https://scienceillustrated.com.au/blog/nature/ask-us-what-gives-bird-feathers-their-colours/#:~:text=Pigments%20called%20melanins%2C%20carotenoids%20and,skin%20produce%20most%20feather%20colours.&text=Bright%20red%2C%20yellow%20and%20orange,generally%20get%20from%20eating%20plants.).

However, when bare skin changes from flesh-coloured to reddish, this is usually the colour of blood, not just pigments.

Skin can look blood-red, because the capillaries just beneath the skin dilate enough for oxygenated blood to show through. The red is the hue of hemoglobin (https://en.wikipedia.org/wiki/Hemoglobin), which can be called a pigment but is the substance that transports oxygen in the blood.

And, in photogenic animals ranging from birds to large mammals, bare skin can be designed to become bloodshot.

In some cases this is a social/sexual display, and in others the red skin acts as a radiator of excessive bodily heat in hot weather. This aid to thermoregulation can be particularly valuable in dry climates where water tends to be unaffordable for sweating.

The most familiar example is the comb of the domestic fowl (Gallus gallus).

The skin and the capillary walls are translucent enough that the comb can look blood-red (https://animals.mom.com/changes-in-the-color-of-a-roosters-comb-12624586.html and https://www.yourchickens.co.uk/care-and-advice/skin-and-feathers-1-1013807 and https://chickens.fandom.com/wiki/Earlobes). Although this may intensify in hot weather, its functions are mainly social/sexual in birds.

A similar but less obvious effect occurs in the ostrich (Struthio camelus).

The neck of adult males becomes bloodshot in the breeding season (https://www.alamy.com/stock-photo-ostrich-struthio-camelus-camelus-red-necked-subspecies-143922867.html and https://www.alamy.com/stock-photo-ostrich-male-red-neck-during-mating-season-55967022.html and https://twitter.com/brglilly/status/598563930877878272).

This is for sexual display, rather than thermoregulation. However, the important point is that the hue in the skin is that of blood, not that of the carotenoid pigments for which the feathers of flamingoes are so well-known (https://www.britannica.com/story/why-are-flamingos-pink).

In mammals, subtle effects of a similar kind have been overlooked. This is partly because they tend to be restricted to the ear pinnae, which are widely assumed to be large for hearing rather than the radiation of excessive heat.

For example, who has previously noticed the following?
https://www.dreamstime.com/stock-photo-eye-deer-persian-fallow-dama-mesopotamica-ear-image81204749.

So, let us look at some large-eared mammals adapted to hot climates.

Some photos of hares (Lepus) suggest bloodshot ears in hot weather. In cool weather, the ear pinnae are translucent but flesh-coloured: https://www.dreamstime.com/full-body-portrait-african-hare-lepus-capensis-backlit-large-ears-eating-leaf-sitting-grass-next-to-dirt-road-image131453041.

However, in the following the hue has intensified to reddish: https://upload.wikimedia.org/wikipedia/commons/4/44/Lepus_europaeus_%28Causse_M%C3%A9jean%2C_Loz%C3%A8re%29-cropped.jpg. The following are not necessarily bloodshot but clearly show the blood vessels: https://i.redd.it/7jyb9cu0s5r61.jpg and https://www.jungledragon.com/image/69607/black-tailed_jackrabbit.html.

UNGULATES

Among ungulates, the examples I have found are mainly in the subfamily Bovinae (https://en.wikipedia.org/wiki/Bovinae) of the family Bovidae.

PLEASE NOTE: In each case I illustrate the ear first flesh-coloured, then bloodshot in what is presumably hot weather, the latter being asterisked*.

CERVIDAE

Rusa unicolor

https://www.pond5.com/stock-footage/item/59088273-sambar-deer
https://www.shutterstock.com/image-photo/sambar-deer-124184467
https://www.shutterstock.com/image-photo/closeup-face-male-sambar-deer-forest-1268977681

*https://www.shutterstock.com/image-photo/female-sambar-deer-on-alert-tigers-2045928401
*https://www.shutterstock.com/image-photo/female-sambar-deer-on-alert-tigers-2045928404
*https://www.shutterstock.com/image-photo/female-sambar-deer-on-alert-tigers-2045928407
*https://www.shutterstock.com/image-photo/female-sambar-deer-rusa-unicolor-khao-1884819523
*https://fineartamerica.com/featured/male-sambar-deer-close-up-ndp.html
*https://stock.adobe.com/images/face-of-sambar-deer-in-forest-thailand/202200603

Odocoileus hemionus

https://windling.typepad.com/.a/6a00e54fcf73858834017ee3ca2116970d-pi
https://www.dreamstime.com/stock-photo-young-mule-deer-buck-listens-carefully-large-ears-predators-image92730853
https://thumbs.dreamstime.com/z/deer-huge-ears-mule-looking-directly-camera-has-grass-s-mouth-57985614.jpg

*https://www.dreamstime.com/eyes-have-mule-deer-colorado-aspen-grove-doe-froze-seconds-july-pm-natural-beauty-curiousn-intrigued-image161491889
*https://img0.etsystatic.com/074/0/11096458/il_340x270.822181242_p1yy.jpg

BOVIDAE

Strepsiceros strepsiceros

https://www.dreamstime.com/royalty-free-stock-photos-female-kudu-antelope-image16919768
https://www.dreamstime.com/stock-image-kudu-antelope-female-image22113571
https://t3.ftcdn.net/jpg/00/98/70/28/240_F_98702838_yzg7r4EIDx6tcQUl8DhgNX2NGpFtNLKB.jpg

*https://i.pinimg.com/736x/10/e4/3b/10e43b9e1c3d3b1e31029f4737399a04.jpg
*https://i.pinimg.com/236x/a1/51/3b/a1513b0f6d11dd0be857b46055270457.jpg
*https://www.dreamstime.com/stock-photo-close-up-female-kudu-looking-directly-ahead-isolated-large-ears-image63183597
*https://www.agefotostock.com/age/en/details-photo/kudu-antelope-ears/ESY-012245060
*https://elements.envato.com/greater-kudu-cow-looking-forward-with-pointed-ears-75HYTFX
*https://www.alamy.com/stock-photo-portrait-of-a-kudu-antelope-tragelaphus-strepsiceros-kruger-national-36406290.html
*https://www.facebook.com/thesavetheearthfoundation/photos/beautiful-kudu-antelope/10156804168193883/
*https://www.dreamstime.com/royalty-free-stock-photo-kudu-doe-portrait-image23041455
*https://www.dreamstime.com/royalty-free-stock-photography-portrait-female-kudu-southern-africa-image12102547
*https://www.dreamstime.com/greater-kudu-tragelaphus-strepsiceros-handsome-antelope-spiral-horns-animal-green-meadow-habitat-okavango-delta-moremi-image150420507
*https://www.dreamstime.com/greater-kudu-tragelaphus-strepsiceros-handsome-antelope-spiral-horns-animal-green-meadow-habitat-okavango-delta-moremi-image150422312
*http://www.shadowsofafrica.com/media/catalog/product/cache/1/image/900x/040ec09b1e35df139433887a97daa66f/r/u/ruaha_kudu_1.jpg

Ammelaphus imberbis

*https://www.dreamstime.com/stock-photo-female-lesser-kudu-wild-tragelaphus-imberbis-hiding-shade-acacia-tree-tsavo-east-national-game-park-kenya-slim-image85101068

Taurotragus oryx

https://www.dreamstime.com/young-female-eland-antelope-portrait-common-eland-taurotragus-oryx-also-known-as-southern-eland-eland-antelope-image221318581

*https://behindthethrills.com/wp-content/uploads/2011/08/BabyEland1.jpg

https://previews.123rf.com/images/joefke/joefke0908/joefke090800091/5391145-Female-eland-antilope-Stock-Photo-eland.jpg
https://www.theanimalfacts.com/wp-content/uploads/2015/04/Eland-featured.jpg

*https://www.dreamstime.com/stock-photo-mature-common-eland-buck-very-large-aka-southern-antelope-old-male-standing-savanna-nairobi-national-image83380150

Syncerus caffer

https://www.dreamstime.com/royalty-free-stock-image-cape-buffalo-standing-looking-image29646066
https://www.dreamstime.com/stock-photo-cape-buffalo-feeding-lily-pads-choebe-river-image85656649
https://www.dreamstime.com/stock-photo-african-cape-buffalo-portrait-large-curved-horns-beady-eyes-image75599885
https://www.dreamstime.com/cape-buffalo-facing-camera-sunlit-savannah-cape-buffalo-facing-camera-sunlit-savannah-image158242664
https://l7.alamy.com/zooms/39ef80e3333847bab1dbd0cba76cee93/close-up-of-cape-buffalo-greater-kruger-national-park-south-africa-ayh13n.jpg

*https://www.dreamstime.com/stock-image-cape-buffalo-image3988891
*https://www.istockphoto.com/photo/cape-buffalo-with-beautiful-ears-gm948580952-258972570
*https://www.dreamstime.com/royalty-free-stock-photo-cape-buffalo-image9337875
*https://www.dreamstime.com/stock-photos-cape-buffalo-bull-image12757143
*https://www.dreamstime.com/stock-images-cape-buffalo-syncerus-caffer-image3673374
*https://www.alamy.com/stock-photo-close-up-of-cape-buffalo-greater-kruger-national-park-south-africa-17107256.html
*https://www.dreamstime.com/stock-photo-cape-buffalo-portrait-grazing-grass-s-mouth-image72100055

(for comparison, in the following there is a bleeding injury on the ear pinna: https://www.dreamstime.com/royalty-free-stock-photography-male-cape-buffalo-synceros-caffer-south-africa-s-mala-mala-game-reserve-image37431597)

Bos indicus

https://www.istockphoto.com/photo/pretty-little-calf-standing-alone-in-a-stall-gm467528694-60384158
https://www.alamy.com/stock-photo-young-calf-with-big-floppy-ears-seen-in-the-town-of-guane-colombia-126933243.html

*https://www.alamy.com/stock-photo-zebu-cattle-10830070.html
*http://jeffshea.org/photos/thailand-loei-prov-long-eared-cow-2008-img-6452/

Raphicerus campestris, Ourebia ourebi, and Litocranius walleri (see comments below)

הועלה ב-ספטמבר 14, 2021 01:31 אחה"צ על ידי milewski milewski

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פורסם על-ידי milewski לפני יותר מ 2 שנים

Photos of ear pinnae of steenbok (Raphicerus campestris), show panels that hypothetically open and close, to regulate body temperature. 

The following show the panels of somewhat bloodshot, bare skin, exposed in what is presumably hot weather. The mechanism seems to be pilo-erection of the rows of stiff whitish hairs.

https://s-media-cache-ak0.pinimg.com/564x/94/ce/d9/94ced97ffa3078f6f1989753413cd31b.jpg

https://www.shutterstock.com/image-photo/marshmallow-hot-chocolate-710181256

http://elelur.com/data_images/mammals/steenbok/steenbok-08.jpg

https://www.inaturalist.org/observations/18013088

The following show the panels closed, in what is presumably cool weather. The mechanism seems to be the relaxation of the pilo-erection, allowing the hairs to return to covering the bare skin.

https://depositphotos.com/30111255/stock-photo-steenbok-standing-in-scrub-in.html

https://www.redbubble.com/i/canvas-print/Young-Male-Steenbok-Up-Close-by-Mytmoss/4662454.5Y5V7#&gid=1&pid=3

https://www.shutterstock.com/image-photo/steenbok-aka-steinbuck-steinbok-antelope-male-140463946

https://www.shutterstock.com/image-photo/steenbok-aka-steinbuck-steinbok-male-portrait-140509582

Scroll to second photo in https://africawild-forum.com/viewtopic.php?p=234338#p234338

פורסם על-ידי milewski לפני יותר משנה

Litocranius walleri is, like Raphicerus campestris, a member of the Antilopini (https://en.wikipedia.org/wiki/Antilopini).

The anatomy of the ear pinna in Antilopini differs from that in Bovinae, despite both belonging to the family Bovidae.

In Antilopini, the heat-radiating surface is less obvious than in Bovidae, because a) a bloodshot appearance tends to be hidden by pigmentation, and/or b) the mechanism of regulation is not only changes in the flow of blood, but also the opening and closing of hair-curtains.

The following show the hair-curtains open, presumably in hot weather:

https://www.alamy.com/female-gerenuk-litocranius-walleri-head-portrait-samburu-national-reserve-kenya-africa-image262992354.html?imageid=AC66618E-6178-4227-9100-CEBB0561B02C&p=215444&pn=2&searchId=a7d844d3e9452cbe08975d0b9758921b&searchtype=0

https://www.dreamstime.com/royalty-free-stock-photography-antelope-close-up-detail-african-gerenuk-face-big-ears-image30627197

https://m.facebook.com/AfricanWildlifeFoundation/photos/a.451901523948/10160403738853949/

The following shows the hair-curtains relatively closed:

https://www.alamy.com/head-and-neck-of-a-female-gerenuk-litocranius-walleri-image266445709.html?imageid=EA271F84-AD3E-4641-B71C-BDD25DC0F376&p=195735&pn=1&searchId=0a18ce30c898a9b9641d54da74fc2b1d&searchtype=0

The ear pinnae of Litocranius differ from those of Raphicerus and Ourebia, in that a) the bare skin is intensely pigmented in the former but not in the latter, and b) the hair-curtains may not extend to the centre of the pinna in the former, whereas they do in the latter.

פורסם על-ידי milewski לפני יותר משנה

The following is a particularly striking photo of the bloodshot effect on the ear pinnae of Strepsiceros strepsiceros zambesiensis:

https://es.123rf.com/photo_55900798_kudu-en-parque-nacional-kruger-sud%C3%A1frica.html?vti=mrg5kps8d5ojsz19kg-2-109

פורסם על-ידי milewski לפני יותר משנה

The following shows the bloodshot effect in infants in Strepsiceros. This is noteworthy because heat-stress is not expected at small body sizes.

https://www.istockphoto.com/photo/calf-kudu-buck-wildlife-gm484853222-71562255?phrase=tsessebe%20antelope%20calf

פורסם על-ידי milewski לפני 12 חודשים

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