Does the sable antelope (Hippotragus niger) possess a bleeze? part 2: sexual and ontogenetic development of the ischio-abdominal pattern in the southern sable antelope (H. n. niger)

...continued from https://www.inaturalist.org/journal/milewski/88983-does-the-sable-antelope-hippotragus-niger-possess-a-bleeze-part-1#

Also see https://www.inaturalist.org/posts/86047-does-the-sable-antelope-hippotragus-niger-possess-a-caudal-flag#

Hippotragus niger,

• unlike other hippotragin bovids, shows obvious sexual dimorphism in colouration (https://goseedo.co.za/places/sable-ranch/ and https://www.alamy.com/two-giant-sable-antelope-with-sable-antelope-cow-south-africa-image625053.html?imageid=857E1C13-E861-4A0B-8B23-1C0C321BC978&p=5008&pn=1&searchId=0452b29cb4460d2129648a818706996d&searchtype=0), and
• like other hippotragin bovids, is born with colouration different from that of adults (https://www.alamy.com/in-this-june-20-2018-photo-a-baby-sable-antelope-born-may-13-nuzzles-his-mother-at-the-audubon-species-survival-center-in-new-orleans-about-a-year-after-moving-into-spacious-new-digs-in-new-orleans-african-animals-are-doing-just-what-officials-from-two-zoos-had-hoped-being-fruitful-and-multiplying-ap-photogerald-herbert-image511985143.html).

In this Post, I have chosen photos from the Web to show the development of the ischio-abdominal pattern from birth to full maturity, comparing females with males.

Neonates:

The buttocks and abdomen are already pale at birth. However, the colouration is inconspicuous, partly because the tail - apart from its tip - is not yet dark.

https://stock.adobe.com/images/newly-born-sable-antelope/327612832?prev_url=detail

https://www.zoobasel.ch/en/aktuelles/news/1152/rappenantilopen-nachwuchs-im-zoo-basel/

https://www.alamy.com/stock-photo-sable-antelope-hippotragus-niger-calf-mokala-national-park-south-africa-125537967.html?imageid=FCACD879-F138-4D2F-82DD-EAC0D9DD0114&p=361664&pn=1&searchId=70d6cc7e51432aae845f0cf4336901c8&searchtype=0

https://stock.adobe.com/images/young-sable-antelope-in-its-habitat/606417953?prev_url=detail

https://stock.adobe.com/images/sable-antelope-herd-and-portrait-in-south-africa/311059045?prev_url=detail

Infants/small juveniles:

From one to six months old, the body mass increases severalfold.

During this period, the tail gradually darkens (https://www.123rf.com/photo_6756331_young-roan-antelope-looking-toward-something-with-small-horns.html and https://www.alamy.com/stock-photo-female-sable-antelope-and-three-foals-31832572.html?imageid=51818820-A1ED-4766-AE1D-D046F48318E7&p=34420&pn=1&searchId=0e6e39bb562061c5ecf0ff4fe4026297&searchtype=0). However, this is not precocial compared to the mane, which is so precocial that it attains noticeable darkness before the horns have lengthened beyond a token appearance (mere short spikes).

By 6 months old, the ground colour has already darkened in some individuals, despite the horns being only a third of the length of the ear pinna.

https://www.alamy.com/sable-antelope-young-image781774.html?imageid=D76B1E66-D42C-4736-85FE-FE5C72BF65FF&p=4877&pn=1&searchId=6b10a9d1bb66e7ff82c62b28f6726248&searchtype=0

https://www.alamy.com/young-sable-antelope-hippotragus-niger-calf-in-grassland-south-africa-image68981373.html?imageid=2EE0C082-71E1-4C7E-AAA4-D1EEC76204A6&p=70019&pn=1&searchId=70d6cc7e51432aae845f0cf4336901c8&searchtype=0

https://www.alamy.com/a-matriarchal-herd-of-southern-sable-antelopes-hippotragus-niger-niger-walking-across-the-red-sand-dunes-of-the-kalahari-desert-namibia-africa-image467922320.html?imageid=D5B0A88D-AADB-4F0F-AC80-85AA44FB4088&p=147259&pn=1&searchId=70d6cc7e51432aae845f0cf4336901c8&searchtype=0

https://www.alamy.com/stock-photo-a-juvenile-sable-antelope-in-southern-african-savanna-141049135.html?imageid=79474391-CAF2-46E4-A242-116B78731477&p=291902&pn=1&searchId=70d6cc7e51432aae845f0cf4336901c8&searchtype=0

https://www.alamy.com/stock-photo-a-family-group-of-sable-antelopes-hippotragus-niger-in-natural-habitat-83028985.html?imageid=FB5FA007-BDAE-48BE-BE1A-7686C714CE27&p=70019&pn=1&searchId=70d6cc7e51432aae845f0cf4336901c8&searchtype=0

https://stock.adobe.com/images/sable-antelope-calf/64526610?prev_url=detail

https://stock.adobe.com/images/sable-antelope/221707903?prev_url=detail

In some individuals, the ground colour starts to darken, before the tail is dark (https://stock.adobe.com/images/sable-antelopes-hippotragus-niger-khwai-concession-okavango-delta/583889458?prev_url=detail).

Juveniles:

By 18 months old, when the horns have reached double the length of the ear pinnae,

• the ground colour has darkened and
• the tail has become dark and has acquired its tassel.

A crisp contrast between pale and dark has developed at the abdomen but not at the buttocks, whereconspicuousness remains limited because

• the border of the whitish pelage on the buttocks is blurry, and
• the ground colour on the haunches remains similar to that in infants.

What this means is that, at 18 months old, the ischio-abdominal bleeze remains ambivalent.

https://www.dreamstime.com/sable-antelope-kruger-national-park-image207176968

https://stock.adobe.com/images/sable-antelope-hippotragus-niger/114901543?prev_url=detail

https://stock.adobe.com/images/sable-antelope-hippotragus-niger/340288554?prev_url=detail

https://stock.adobe.com/images/sable-antelope-hippotragus-niger/138483689?prev_url=detail

Adolescent females:

By 3 years old, the horns are 3-4-fold the length of the ear pinnae. However, the development of the colouration w.r.t. the ischio-abdominal pattern has hardly proceeded over the 1.5 years additionally elapsed.

https://www.dreamstime.com/sable-antelope-kruger-national-park-image207177444

https://www.dreamstime.com/sable-antelope-kruger-national-park-image207177204

https://stock.adobe.com/images/female-sable-antelope/69829755?prev_url=detail

https://stock.adobe.com/images/rare-sable-antelope-hippotragus-niger-south-africa/16532032?prev_url=detail

Adult but not mature females:

At about 5 years old, the whitish pelage on the buttocks has acquired a fairly crisp border. However, the pattern remains ambivalent, because the haunches remain medium in tone.

https://www.shutterstock.com/image-photo/sable-antelope-kruger-national-park-2339481987

https://www.alamy.com/sable-antelope-hippotragus-niger-female-okonjima-nature-reserve-namibia-africa-image230532688.html

https://www.dreamstime.com/sable-antelope-kruger-national-park-image207177241

https://www.dreamstime.com/sable-antelope-kruger-national-park-image207177299

https://southafricadiscovery.files.wordpress.com/2011/10/img_0408.jpg

https://www.citizen.co.za/sandton-chronicle/news-headlines/2016/09/08/mokala-sable-has-come-a-long-way/

https://howieswildlifeimages.files.wordpress.com/2022/05/2021-09-12_m1x-p9120565.jpg

https://stock.adobe.com/images/sable-antelope-kruger-national-park/629029950?prev_url=detail

https://stock.adobe.com/images/rare-sable-antelope-hippotragus-niger/117717047?prev_url=detail

https://stock.adobe.com/images/pair-of-sable-antelope-females-moving-through-the-dense-bush-browsing/303841641?prev_url=detail

https://stock.adobe.com/images/female-sable-antelope-hippotragus-niger/73225436?prev_url=detail

Mature females:

From 6 years onward, the ground colour darkens further, and this finally extends to the haunches, at least in some individuals.

This brings the ischio-abdominal bleeze to completion by about 8 years old, in females.

https://www.alamy.com/sable-antelope-hippotragus-niger-niger-chamabonda-game-reserve-zimbabwe-image3084854.html?imageid=B596DC62-728F-4149-AD1F-82014E7DA4A0&p=9122&pn=1&searchId=0e6e39bb562061c5ecf0ff4fe4026297&searchtype=0

https://upload.wikimedia.org/wikipedia/commons/3/3a/Sable_%28Hippotragus_niger%29_female_crossing_the_road_%2816635641913%29%2C_crop.jpg

https://www.wild4photographicsafaris.com/photo-safaris/view/kruger-national-park-photo-safari-august-2023#images-7

https://www.alamy.com/sable-antelope-image472069428.html?imageid=63E4EF4B-C67D-4279-8ADA-838EB08A6134&p=1879136&pn=6&searchId=29384e0433d380722fb68e25119a69b6&searchtype=0

https://www.alamy.com/stock-photo-sable-hippotragus-niger-female-adult-and-calf-kruger-national-park-48784479.html?imageid=339B6EB3-38DD-4099-9717-51CB47A76D88&p=165079&pn=1&searchId=70d6cc7e51432aae845f0cf4336901c8&searchtype=0

https://www.alamy.com/sable-antelope-hippotragus-niger-family-two-parents-with-calf-chobe-national-park-botswana-image550660749.html?imageid=C7F2AB70-FBB3-4BAF-8580-10A8D6DA953B&p=2164234&pn=1&searchId=70d6cc7e51432aae845f0cf4336901c8&searchtype=0

https://stock.adobe.com/images/sable-antelope-herd-and-portrait-in-south-africa/311058799?prev_url=detail

In full maturity, some individuals attain colouration identical - except for the absence of a prepuce - to that of mature males (https://howieswildlifeimages.files.wordpress.com/2013/05/chobe-1-6_may1313901.jpg and https://howieswildlifeimages.files.wordpress.com/2013/05/chobe-1-6_may131413.jpg and scroll to 13th photo in https://howieswildlifeimages.com/2017/04/01/sable-antelope-emperor/).

Juvenile/adolescent males:

https://www.alamy.com/sable-antelope-hippotragus-niger-in-wooded-savanna-mokala-national-park-south-africa-image554349069.html?imageid=B4312978-4237-456C-B48C-9156D75EA608&p=824482&pn=2&searchId=55443a42a50ba8966706d442a2e6b767&searchtype=0

In the following, the individual on the right is a male of about 4 years old (https://stock.adobe.com/search?k=%22sable+antelope%22&asset_id=417366825).

By 2 years old, the ischio-abdominal bleeze becomes unambivalent in some individual males. This means that males can attain this bleeze about 4 years before females.

However, some individual males remain similar in colouration to females, even at about 3 years old (https://stock.adobe.com/images/one-sable-antelope-hippotragus-niger-walking-in-savanna-with-bushes/248840474?prev_url=detail).

Adolescent/adult males:

By about 6 years old, most male individuals have attained the full expression of the ischio-abdominal pattern. Some individuals are already fully dark. However, in most the ground colour has not yet become blackish.

https://www.robertharding.com/preview/764-5112/sable-antelope-hippotragus-niger-male-kruger-national-park/

https://stock.adobe.com/images/small-group-of-mature-sable-antelope-on-a-farm-in-south-africa/143805185?prev_url=detail

https://www.alamy.com/three-beautiful-sable-antelopes-walking-across-the-dry-yellow-savannah-in-hwange-national-park-zimbabwe-with-a-natural-bush-background-image371221194.html?imageid=0B7B0DCB-02DA-4CBB-8FAF-0235F47F2B64&p=364701&pn=1&searchId=0e6e39bb562061c5ecf0ff4fe4026297&searchtype=0

https://stock.adobe.com/images/sable-antelope-hippotragus-niger/5238202?prev_url=detail

https://www.alamy.com/three-male-sable-antelopes-standing-in-the-dry-yellow-grass-on-the-african-savannah-hwange-national-park-zimbabwe-image371220361.html?imageid=119695AA-4868-406F-B049-1443BE84384C&p=364701&pn=1&searchId=0e6e39bb562061c5ecf0ff4fe4026297&searchtype=0

Mature males:

Male individuals older than 8 years have generally become blackish, with the white of the abdominal and (to a slightly lesser degree) ischial surfaces crisply-defined. Females and males do not seem to differ in the age at which the fully mature colouration is attained in most individuals.

In other words, any specimen of the sable antelope showing fully 'black-and-white' colouration (which excludes the posterior surfaces of the ear pinnae) is probably >8 years old.

An unexplained quirk of colouration is that the hocks tend to be resistant to blackening (https://www.robertharding.com/preview/764-5112/sable-antelope-hippotragus-niger-male-kruger-national-park/). However, this seems insignificant adaptively, because the hocks never present pale/dark contrast, at any distance.

https://www.alamy.com/south-africa-kalahari-desert-sable-antelope-hippotragus-niger-adult-male-image208258011.html?imageid=E7AB9A38-1C88-4A45-9594-18715D10209B&p=158369&pn=5&searchId=4d6c3d36cc656d6b0d11b247299e7160&searchtype=0

https://www.alamy.com/sable-antelope-hippotragus-niger-gondwana-game-reserve-south-africa-image337985633.html

https://www.mediastorehouse.com.au/flpa/sable-antelope-hippotragus-niger-adult-male-6542627.html

Also see https://www.inaturalist.org/journal/milewski/87728-is-the-sable-antelope-the-only-ungulate-indeed-mammal-that-advertises-its-penis-with-black-and-white-punctuation#.

Posted on December 27, 2023 04:06 PM by milewski