Does the sable antelope (Hippotragus niger) possess a caudal flag?

In terms of adaptive colouration, a flag is a feature too small to advertise the stationary figure at distance, but presenting enough dark/pale contrast to draw attention to the animal when it moves.

Flags are biologically significant because many animals rely on a combination of concealment and advertisement. Concealment is mainly an anti-predator strategy. Advertisement is used sexually and socially, and in certain species is also part of an anti-predator strategy.

A caudal flag, by definition, refers to the tail (https://www.etymonline.com/word/caudal#:~:text=caudal%20(adj.),%2B%20%2Dal%20(1).), in some cases including the surfaces immediately adjacent to the tail.

The colouration of the tail in the sable antelope (Hippotragus niger) makes this a candidate for a caudal flag.

This is because the tail is

However, there are several aspects detracting from the conspicuousness of the colouration of the tail in the sable antelope, and potentially disqualifying a caudal flag in this species.

These are

The strongest case for a caudal flag can be made for the northernmost subspecies, Hippotragus niger roosevelti, in which the black tail is particularly conspicuous in

The sable antelope sometimes raises the tail towards the horizontal while fleeing. However, this seems to be mainly during initial acceleration, being otherwise done in a loose/erratic/non-stereotyped way (https://www.mindenpictures.com/stock-photo-sable-antelope-hippotragus-niger-buck-fleeing-the-river-bank-chobe-naturephotography-image00548856.html and https://www.youtube.com/watch?v=g0u0TbaAY7A and https://www.alamy.com/stock-photo-sable-antelopes-hippotragus-niger-bovidae-at-full-gallop-in-mopane-36820723.html?imageid=501E220A-5A08-4F53-AFB3-D6BB8482AB1F&p=26096&pn=1&searchId=0e6e39bb562061c5ecf0ff4fe4026297&searchtype=0 and https://howieswildlifeimages.files.wordpress.com/2017/03/20151014-d4s_4575.jpg).

However, anti-predator flagging of the tail is shown in the following footage:

Estes (1991, pages 125-127) mentions the following displays of the tail:

Skinner and Chimimba (2005, page 664) state:
"Territorial defence...displays...lateral presentation of the body to the trespasser, the tail held out stiffly and twitching, as the two [mature male rivals] stand near to tail."

DISCUSSION

The sable antelope certainly does display its tail to some extent, both in sexual and social contexts and in anti-predator defence.

It may not be particularly significant that the tail is raised as a sign of dominance/confidence/assertiveness, in intraspecific interactions. This is because such displays are widespread among ungulates and carnivores.

On balance, does the sable antelope does not possess a caudal flag?

I am unsure, but an argument can be made that the colouration of the tail in this species be regarded more as part of the ischio-abdominal bleeze.

Compare, for example, the sable antelope with the red hartebeest (Alcelaphus caama).

Both species possess

  • blackish tails with distinct tassels, and
  • conspicuously pale buttocks, contrasting to some degree with both the dark tail and the somewhat dark rump and haunches.

Consequently, in both species an argument can be made for a bleeze on the hindquarters.

However, there is a difference in emphasis.

In the sable antelope, the main elements of conspicuousness are the white abdomen and buttocks, to which the tail seems accessory. By contrast, in the red hartebeest the tail is arguably the crucial element of conspicuousness (https://somethingovertea.files.wordpress.com/2020/01/addoredhartebeest4.jpg).

This is partly because the tassel is larger (https://www.wildwbsafaris.com/p25/species-list/red-hartebeest-in-south-africa.html and https://www.stuporterphotography.com/image/I0000zJVlHwxOnLE) in the red hartebeest than in the sable antelope.

Furthermore, the raising of the tail while running is

Both species style-trot, but only the red hartebeest raises the tail during this display (https://pixels.com/featured/red-hartebeest-running-robert-goodell.html and https://www.dreamstime.com/stock-photo-red-hartebeest-wildlife-background-running-dust-gallops-faded-sunset-light-as-seen-wilds-africa-dusk-image41321838 and https://m.facebook.com/kifaruluxurylodge/photos/pcb.1016673712307255/1016673658973927/?type=3&source=48&).

Also, the darkness of the tail is more precocial in the red hartebeest (https://www.alamy.com/stock-photo-red-hartebeest-alcelaphus-buselaphus-caama-calf-standing-kalahari-96170557.html?imageid=C3A5938E-50E3-4E2B-89C7-C0C178EDD2FB&p=11592&pn=1&searchId=6cb6d804e8c2d0cca41f0eed698c3a54&searchtype=0 and https://www.dreamstime.com/stock-image-baby-red-hartebeest-antelope-image13753251) than in the sable antelope (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 and 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).

As a result, I would argue that

  • the red hartebeest possesses a caudal flag (regardless of whether it qualifies for a bleeze on the hindquarters), whereas
  • the sable antelope does not possess a caudal flag (the conspicuous darkness of the tail instead being one of several elements composing the ischio-abdominal bleeze).

In the case of females of H. niger roosevelti:
My interpretation is that, in the absence of darkness on the rump, haunches, and upper hindlegs, the tail is the most important element in the ischio-abdominal bleeze (http://www.wild-about-you.com/GameEastAfricanSable.htm and https://www.wildlifeofkenya.com/categories/ongulates/antelope-sable/ and https://www.alamy.com/stock-photo-adult-female-sable-antelope-in-the-shimba-hills-reserve-mombasa-kenya-18912923.html?imageid=96807F0A-EBB3-41F0-8578-4D5BBF1428DB&p=30436&pn=1&searchId=5025017ea04e94a5648cb5917feeee17&searchtype=0 and https://www.alamy.com/roosevelts-sable-image356968100.html?imageid=08F419C3-5193-455E-872A-53BAAAAB6F29&p=557829&pn=1&searchId=5025017ea04e94a5648cb5917feeee17&searchtype=0 and https://www.alamy.com/sable-antelope-hippotragus-niger-in-the-grassy-savannah-of-shimba-hills-national-park-kenya-image233626771.html?imageid=68D04909-9A31-4BE8-9D45-5B22E243FE3A&p=785530&pn=1&searchId=5025017ea04e94a5648cb5917feeee17&searchtype=0 and https://www.alamy.com/stock-photo-adult-female-sable-antelope-in-the-shimba-hills-reserve-mombasa-kenya-18911692.html?imageid=BB9A5394-F007-4212-82BE-CC43A1025C5B&p=30436&pn=1&searchId=5025017ea04e94a5648cb5917feeee17&searchtype=0 and https://www.alamy.com/stock-photo-sable-antelope-hippotragus-niger-roosevelti-shimba-hills-national-31135025.html?imageid=77492FE9-AB45-46AE-9209-A7B55BA5735F&p=74587&pn=1&searchId=5025017ea04e94a5648cb5917feeee17&searchtype=0).

AUDITORY INSTEAD OF VISUAL SIGNALLING?

One adaptive interpretation of the lack of caudal flags in Hippotragus is as follows.

The sable antelope and the roan antelope (Hippotragus equinus) are unusually vocal for antelopes. In the case of the former species, Estes (1991, pages 125-127) mentions that

  • when the mature male individual of a group disciplines adult group-members, it bellows aggressively, while the victimised individual 'often cries out' in fear,
  • when an individual female, in pre-oestrus condition, was aggressively courted by the mature male of the group, this was 'punctuated by his bellows and her drawn-out cries'. and
  • 'an 'abandoned' calf eventually begins calling..., uttering ever-louder cries. Mothers that have misplaced calves...wander around giving the same birdlike call in a lower register until they find them'.

Also see in https://www.inaturalist.org/journal/milewski/86153-most-ungulates-are-surprisingly-inept-at-using-their-horns-against-predators-part-2-is-the-sable-antelope-hippotragus-niger-really-an-exception#, under the heading ADDITIONAL NOTES.

I therefore suggest that vocalisation is, in part, an auditory substitute for caudal flagging in Hippotragus.

However, this applies only to sexual and social functions of flagging, excluding anti-predator contexts. Hippotragus (and hippotragins generally) seems to lack the caudal flagging seen in various other ungulates as they interact with predators.

Posted on October 19, 2023 11:53 PM by milewski milewski

Comments

Scroll to 8th photo in http://elelur.com/mammals/sable-antelope.html#photo_8 for fully mature male Hippotragus niger niger, clearly showing the size and shape of the tail.

Posted by milewski 7 months ago

Always fascinated by the Angolan giant sable, though I've only seen taxidermy of some specimens at AMNH

Posted by paradoxornithidae 7 months ago

Reference:
Estes R D and Estes R K (1969) The Shimba Hills sable population. First progress report, Hippotragine Antelope Study. National Geographic Society.

Masculine rivalry in Hippotragus niger roosevelti

Page 12:
"The sable's Lateral Intimidation Display, in which two bulls stand parallel or facing with heads high, necks arched, chins in, and tails stiffly out, is most impressive."

Page 13:
"Sub-adult males...When confronted by a demonstrating mature bull, the inferior animal puts his head low, clamps his tail between his legs, and scurries around behind the displaying male...Intimidated females behave similarly."

Posted by milewski 5 months ago

Add a Comment

Sign In or Sign Up to add comments
Member of the iNaturalist Network   |   Powered by iNaturalist open source software |   Documentation for developers