A photo-guide to the two most different subspecies of the roan antelope: Hippotragus equinus koba of West Africa versus Hippotragus e. equinus/cottoni of southern Africa

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INTRODUCTION

The roan antelope (Hippotragus equinus, https://www.inaturalist.org/taxa/42332-Hippotragus-equinus) is an unusually widespread species of African bovid.

It spans the continent from far-West Africa to Eritrea, and southward to subtropical South Africa (https://upload.wikimedia.org/wikipedia/commons/e/e1/Roan_Antelope_Hippotragus_equinus_distribution_map.png and https://www.researchgate.net/figure/21-The-geographic-range-of-roan-antelope-in-the-1800s-Du-Plessis-1969-and-today-IUCN_fig2_278698501).

Given this vast range, we might expect that distinct subspecies occur (https://www.researchgate.net/figure/The-distribution-of-roan-antelope-in-Africa-Anonymous-2006-with-subspecies-delineations_fig1_290478320).

However, Groves and Grubb (2011, pages 198-201, including Table 53, in https://zmmu.msu.ru/files/%D0%91%D0%B8%D0%B1%D0%BB%D0%B8%D0%BE%D1%82%D0%B5%D0%BA%D0%B0%20%D0%9F%D0%B0%D0%B2%D0%BB%D0%B8%D0%BD%D0%BE%D0%B2%D0%B0/grubb-groves-2011_taxonomy_ungulates.pdf), in their taxonomic revision of all the ungulates of the world, failed to verify any subspecies of the roan antelope.

Their revision was based on museum specimens, ignoring photographic evidence such as that now available electonically.

Factors that have retarded/complicated verification of subspecies of the roan antelope in the past include:

individual variation combined with small numbers of specimens from any given geographical area (Groves and Grubb 2011),
far more sexual dimorphism in South Sudan than at similar latitudes in West Africa (Groves and Grubb 2011),
questionable disjunction in the distribution of the nominate subspecies, between South Africa and Namibia, and
the lack, to this day, of photos of bakeri/doggetti/scharicus in inaccessible South Sudan (https://news.mongabay.com/2007/06/massive-wildlife-population-discovered-in-southern-sudan/).

MY APPROACH: HIPPOTRAGUS EQUINUS KOBA Vs HIPPOTRAGUS EQUINUS EQUINUS/COTTONI

My perusal of observations in iNaturalist, and photos elsewhere on the Web, has shown certain fairly consistent differences, particularly in colouration, between the subspecies at the extremes of the geographical range.

Most of these subspecific differences were unbeknownst to Groves and Grubb (2011), and to this day no other taxonomist seems to have noticed them.

Please bear in mind that all of the following are subject to individual variation - which is more important than sexual differences.

The ground-colour of the West African subspecies (H. e. koba) tends to be relatively bright-hued (Groves and Grubb 2011), with minimal grizzling and relatively short pelage. The hues are difficult to compare photographically, owing to vagaries of illumination and technique.

However, the extreme length and pallor of the beard, shown in the following captive specimens of Hippotragus equinus equinus/cottoni, are - as far as I know - never seen in H. e. koba:
adult female https://www.alamy.com/a-close-up-profile-portrait-of-a-roan-antelope-hippotragus-equinus-it-shows-the-head-and-neck-together-with-large-antlers-image429376262.html?imageid=51F04DDC-EFAB-4CE4-B304-781CE27CA2CB&p=224192&pn=3&searchId=907fcf51e051a28f272ac53440026b09&searchtype=0
juvenile https://www.shutterstock.com/image-photo/close-roan-antelope-beautiful-herbivore-1713171139.

Another fairly obvious difference is that, in the West African subspecies (H. e. koba) relative to the southern African subspecies (H. e. equinus/cottoni), dark pelage can be

far more extensive on the face and throat (https://www.shutterstock.com/image-photo/roan-antelope-hippotragus-equinus-savanna-found-1391679614), and
less extensive at the base of the tail (https://www.alamy.com/stock-photo-roan-antelope-hippotragus-equinus-adult-w-regional-park-w-transborder-59189738.html?imageid=66386DE1-36D7-4F8B-A3A8-783EC28B2A82&p=86574&pn=5&searchId=5ed1e1ea051df95555f6aaed35fb537c&searchtype=0).

Let us now examine, in particular, the tendency - consistently visible in photos - for the dark pelage on the face to be more extensive in the West African than in the southern African subspecies.

HOW TO SCRUTINISE THE FACE

A conspicuously pale feature to focus on is the preorbital tuft, located anterior and ventral to the eye.

Dear Reader, can you spot the difference between https://www.inaturalist.org/observations/61091684 and https://www.shutterstock.com/image-photo/roan-antelope-hippotragus-equinus-mammal-1521109436, in the size and shape of the preorbital tuft?

In infancy in both subspecies, the nucleus of the dark 'mask' appears, on

the rostrum (https://www.zoochat.com/community/media/roan-antelope-calf.145764/ and https://www.alamy.com/roan-antelope-hippotragus-equinus-image566951467.html?imageid=031CC98A-793F-47AF-9248-77E53A2E1B61&p=2178539&pn=1&searchId=a5e37347722537f38c2dc3ebc9b10b9f&searchtype=0),
the malar stripe, ventral to the orbit, and
a connection between these, just ventral to the preorbital tuft (https://www.alamy.com/stock-photo-roan-antelope-hippotragus-equinus-juvenile-portrait-native-to-africa-48665346.html).

From this nucleus the darkness spreads (https://www.alamy.com/roan-antelope-hippotragus-equinus-female-both-sexes-have-long-curved-scimitar-shaped-ribbed-horns-black-and-white-facial-markings-long-ears-image398724544.html?imageid=9C93FB19-3D12-4AE0-BF38-AAFEA8A9CAEE&p=77483&pn=1&searchId=a5e37347722537f38c2dc3ebc9b10b9f&searchtype=0), according to age and sex,

towards the horns (https://www.alamy.com/frontal-close-up-of-roan-antelope-father-and-his-son-hippotragus-equinus-image479269495.html?imageid=8B030ADF-1FEC-44C5-939D-2B5288991D72&p=811389&pn=1&searchId=fd85e4ffd7cf9015fd0b98a2e8d73017&searchtype=0),
between the orbit and the base of the ear pinna (https://www.gettyimages.ae/detail/photo/portrait-of-a-male-roan-antelope-south-africa-royalty-free-image/541054616?phrase=these+roan+antelope&adppopup=true and https://www.inaturalist.org/observations/5280586),
in a narrow extension across the white sides of the muzzle towards the upper lip (https://www.inaturalist.org/observations/6572161), and
across the ventral surface of the mandibles (https://www.inaturalist.org/observations/16099553).

This spread tends ultimately to be greater in H. e. koba than in H. e. equinus/cottoni; in fully mature males of the former, the face becomes mainly black.

In H. e. koba, even the following are subject to discoloration in some individuals:

the pale on the nose (i.e. between the rostrum and the rhinarium, (https://www.inaturalist.org/observations/5095492 and https://www.inaturalist.org/observations/6510349 and https://www.inaturalist.org/observations/9979068), and
the pale posterior to the eye (https://www.naturepl.com/stock-photo-roan-antelope-hippotragus-equinus-male-in-profile-fathala-reserve-nature-image01387428.html).

VARIOUS DETAILED DIFFERENCES

Now, let us approach various facial and other features in detail:

In the West African subspecies,

the medium-tone of the forehead can be completely eclipsed by blackish in mature males,
the whitish preorbital tuft tends to be short, leaving a broad tract of blackish on the cheek (https://www.inaturalist.org/observations/6005429),
there is an extension of the facial dark feature on the otherwise whitish sides of the muzzle,
the blackish on the lower jaw can extend to the throat, including both sexes and juveniles (https://www.africaimagelibrary.com/-/galleries/west-africa/senegal/-/medias/4c631c20-2120-11e0-ba98-f50f3d063bc0-roan-antelope-hippotragus-equinus-reserve-de-bandia-senegal and https://www.inaturalist.org/observations/40148214)
pale countershading on the ventral surface of the torso tends to be poorly-developed (https://www.inaturalist.org/observations/195737269),
there tends to be a residual trace of flank-banding posterior to the elbow (https://www.inaturalist.org/observations/39846679),
an indistinctly darkish feature on the mid-line of the rump tends to be poorly-developed (https://www.inaturalist.org/observations/194805493), and the shaft/stalk of the tail is not dark in some individuals, and
a dark/pale pattern on the pasterns and fetlocks tends to be well-developed (https://www.inaturalist.org/observations/6441919 and https://www.inaturalist.org/observations/34295716).

PAIRWISE PHOTO-COMPARISONS

In the following pairwise comparisons, I illustrate the above aspects of ssp. koba of West Africa relative ssp. equinus/cottoni of southern Africa:

DISCUSSION

One of the most remarkable facts about the roan antelope is how little it varies across a vast - and somewhat disjunct - geographical distribution.

As a result, populations more than ten thousand kilometres apart (Senegal, https://upload.wikimedia.org/wikipedia/commons/3/3c/Senegal_%28orthographic_projection%29.svg, versus North West Province of South Africa, https://upload.wikimedia.org/wikipedia/commons/f/fc/North_West_in_South_Africa.svg) appear so similar, in photos, that their subspecific distinction could be doubted.

However, there are two differences that, although slight, may as well be categorical in the overall impression they leave on the human viewer. These are

the southern African subspecies qualifies for the description of 'roan' colouration, whereas the West African subspecies does not, and
in adult males in full-frontal view, the conspicuousness of the face is owing mainly to the blackish component in the West African subspecies, vs the whitish component in the southern African subspecies.

Were it the historical case that the species had become well-known in West Africa (francophone) before South Africa (anglophone), it would probably not have been given the name 'roan antelope' (French: 'antilope rouanne'). A more apt name for H. e. koba might have been 'antilope masquee' ('masked antelope').

This is because the ground-colour in West Africa is not reminiscent of roan colouration in the domestic horse (https://upload.wikimedia.org/wikipedia/commons/f/fc/Red_roan_Quarter_Horse.jpg and https://en.wikipedia.org/wiki/Roan_(color) and https://www.deviantart.com/hunter-raider/art/Coat-Color-Guide-2023-Roan-965502025).

Perhaps the first diagnostic feature to focus on, in most photos, is the preorbital tuft, which is whitish, surrounded by dark, short pelage.

The following, of H. e. equinus/cottoni, show the maximum development of the whitish preorbital tuft:
https://www.shutterstock.com/image-photo/closeup-resting-roan-antelope-hippotragus-equinus-2177832261 and https://www.chesterzoo.org/our-zoo/animals/roan-antelope/.

The following, of H. e. koba, shows how much smaller this feature is in the West African subspecies:
https://www.shutterstock.com/image-photo/roan-antelope-hippotragus-equinus-savanna-found-1391679644.

The difference in the size of the preorbital tuft is

apparent already in infants, and
consistent with the overall difference: H. e. equinus/cottoni is the hairier/shaggier also on the neck/throat, torso, and anterior surface of the ear pinnae.

However, it is noteworthy that

the latter generalisation does not extend to the dark tuft - typical of the whole species - at the tip of the ear pinna. In both subspecies, this feature varies mainly ontogenetically and individually, not geographically, and
the facial emphasis on darkness in H. e. koba does not apply to the ear pinna, which in mature males not only loses the dark tuft seen in juvenile males, but also tends to lose any apical darkness whatsoever.

The West African subspecies is larger-bodied than the southern African subspecies. Mature males weigh respectively about 300 kg and 250 kg (https://sportsafield.com/2021/its-a-roan/).

To the trained eye, this difference is hinted at by the proportionately slightly smaller post-withers mane-tuft in H. e. koba (https://www.inaturalist.org/journal/milewski/87946-has-the-post-withers-mane-tuft-of-hippotragus-evolved-in-mimicry-of-oxpeckers-buphagus-part-1#).

The caudo-ischial flag (https://www.inaturalist.org/posts/85734-oryx-in-posteriolateral-view-an-interspecies-comparison-of-adaptive-colouration#) is somewhat more poorly-developed in H. e. koba than in H. e. equinus/cottoni.

The converse is true in the case of an incipient/residual pedal flag. This pattern is slight, even in H. e. koba.

Publicado el enero 13, 2024 01:27 MAÑANA por

milewski

A photo-guide to the two most different subspecies of the roan antelope: Hippotragus equinus koba of West Africa versus Hippotragus e. equinus/cottoni of southern Africa

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