White on the buttocks: a previously overlooked species-difference in dikdiks of the Madoqua kirkii-Madoqua damarensis complex?

@dejong @tbutynski

In recent Posts, I have shown previously overlooked variation among the species/subspecies in two genera of bambis, namely Ourebia (https://www.inaturalist.org/journal/milewski/70050-the-three-main-types-of-oribi-ourebia-at-a-glance#) and Raphicerus (https://www.inaturalist.org/journal/milewski/70293-the-bambis-part-9-bleezes-flags-and-semets-in-the-bovid-genus-raphicerus#).

I now turn to another genus of bambis, namely Madoqua (https://www.inaturalist.org/observations?place_id=any&taxon_id=42358&view=species).

The species and subspecies of Madoqua may seem too taxonomically complicated for many naturalists to disentangle.

De Jong and Butynski (2017, https://www.lolldaiga.com/wp-content/uploads/De-Jong-Butynski-2017-Madoqua-E-Africa.pdf) have greatly clarified the distinctions among various forms in the kirkii-complex and superficially similar Madoqua guentheri.

However, they seem to have overlooked what is perhaps major variation in adaptive colouration among the species and subspecies in this geographically bewildering set of taxa.

I refer to the incidence, extent, and flaring of whitish pelage on the buttocks - which in some taxa is displayed to potential predators.

What I have noticed, after perusing hundreds of photos, is that there is a range of apparency of white on the hindquarters, as follows:

• maximal in M. guentheri, minimal in M. damarensis (restricted to southern Africa), and intermediate in the kirkii-complex of East Africa, and
• within the kirkii-complex: maximal in nominate kirkii and hindei, vs minimal in thomasi and cavendishi.

In M. guentheri, there is a well-developed, white buttock flag (https://www.inaturalist.org/observations/85335207). This is normally folded out of sight, but is activated in alarm.

In M. damarensis, there no buttock flag. Furthermore, whitish pelage is absent from the buttocks, being restricted to the inner surface of the uppermost hindleg, where it is obscured from view (https://www.alamy.com/damara-dik-dik-on-arid-landscape-image265477351.html?imageid=9918B4C6-E7A2-4558-A9A9-8A4C5986763B&p=925654&pn=2&searchId=812e1b51f3bb17a7cc79ddae25b30690&searchtype=0), even when the animal flees.

In thomasi and cavendishi, the white pelage on the inner upper hindleg hardly reaches the inner surface of the buttock (cavendishi: https://www.inaturalist.org/observations/35760408 ; cavendishi/thomasi: https://www.inaturalist.org/observations/19457512).

Instead, there is a darkened effect, owing to the grey, grizzled pelage on the inner buttock being viewed from a certain angle (also see https://www.inaturalist.org/observations/16658138 and https://www.alamy.com/stock-photo-a-damara-dik-dik-antelope-in-tarangire-national-park-tanzania-125863282.html?imageid=D2243709-A771-41B3-8555-80339AB1FF98&p=149870&pn=1&searchId=a091ff7a0a8c31eef18a8931488c16a4&searchtype=0).

In nominate kirkii and (to a lesser extent?) hindei, considerable whitish is normally apparent on the buttocks. It remains unknown whether this can be activated by piloerection.

What emerges is that, w.r.t. the colouration of the buttocks, the southern and western forms of the kirkii-complex in East Africa may be more similar to the widely disjunct damarensis of southern Africa than they are to nearby kirkii, the nominate, northeasternmost form.

This raises the possibility that there are two species, one of them extremely disjunct - in a biogeographic parallel to sympatric Raphicerus campestris, which also shows wide disjunction between southern and East Africa.

These would be

• a southwesterly species, comprising damarensis (disjunct), thomasi, and cavendishi (https://www.inaturalist.org/observations/57105762), and
• a northeasterly species, comprising nominate kirkii (https://www.alamy.com/stock-photo-dik-dik-madoqua-species-meru-national-park-kenya-the-animal-is-facing-34546136.html?imageid=3A6956A3-7664-4DCD-8AE0-84154B73F32F&p=33818&pn=1&searchId=a091ff7a0a8c31eef18a8931488c16a4&searchtype=0 and https://www.inaturalist.org/observations/137631006) and hindei (https://www.inaturalist.org/observations/66784701).

If so, the basic geographical feature separating the two spp. would be the eastern arm of the Great African Rift (https://en.wikipedia.org/wiki/Great_Rift_Valley#/media/File:Great_Rift_Valley.png), from Lake Turkana (https://en.wikipedia.org/wiki/Lake_Turkana) in the north to Lake Manyara (https://en.wikipedia.org/wiki/Lake_Manyara) in the south.

Such geographical separation would be analogous with that previously recognised between

• Connochaetes albojubatus and Connochaetes mearnsi, and
• Kobus ellipsiprymnus and Kobus defassa.

The following show the buttock flag in Madoqua guentheri:
https://www.inaturalist.org/observations/108449533
https://www.inaturalist.org/observations/109570355.

The following shows that there is no analogous flag in cavendishi/thomasi:
https://www.inaturalist.org/observations/34632953.

GUENTHERI

Many photos of M. guentheri show a whitish horizontal mark on the hindquarters (just below the small tail), which I have never seen in any other species in the genus:

https://www.inaturalist.org/observations/44891973

https://www.inaturalist.org/observations/48668687

https://www.inaturalist.org/observations/92503134

https://www.inaturalist.org/observations/46592563

https://www.inaturalist.org/observations/42815125

https://www.inaturalist.org/observations/34171472

https://www.inaturalist.org/observations/10498051

This indicates a fur-fold which opens out into a broad, white, buttock flag.

This resembles the buttocks in Raphicerus campestris (https://dewetswild.com/tag/steenbok/#jp-carousel-37747). However, it is more pronounced, with a more complex, origami-like unfolding - both vertically and horizontally - of panels of pelage.

KIRKII (nominate)

The following show that there is more extensive white on the hindquarters than in damarensis.

This white pelage is visible without any particular activation, partly because the panel of grizzled, grey pelage of the outer buttock is shorter than in damarensis, thomasi, and cavendishi.

The adaptive colouration thus seems to confirm that damarensis is a different species from nominate kirkii, and not merely a subspecies.

second photo in https://www.inaturalist.org/observations/130962038

https://www.inaturalist.org/observations/104469910

https://www.inaturalist.org/observations/104465769

https://www.inaturalist.org/observations/56610068

https://www.inaturalist.org/observations/127865878

https://www.inaturalist.org/observations/6998029

https://www.inaturalist.org/observations/19215378

https://www.alamy.com/stock-photo-dik-dik-in-the-kenyan-savanna-92694497.html?imageid=D085B884-1918-469D-90A0-4757E0777A4A&p=277251&pn=1&searchId=a091ff7a0a8c31eef18a8931488c16a4&searchtype=0

https://www.inaturalist.org/observations/54460753

https://www.inaturalist.org/observations/104983315

https://www.inaturalist.org/observations/53348887

https://www.inaturalist.org/observations/36294376

https://www.inaturalist.org/observations/135184955

https://www.inaturalist.org/observations/66263881

https://www.inaturalist.org/observations/104982491

https://www.inaturalist.org/observations/66064513

https://www.inaturalist.org/observations/104982477

https://www.inaturalist.org/observations/104982469

https://www.inaturalist.org/observations/66101649

https://www.inaturalist.org/observations/104982481

https://www.inaturalist.org/observations/104982488

https://www.inaturalist.org/observations/104982474

https://www.inaturalist.org/observations/104982464

https://www.inaturalist.org/observations/94054422

https://www.inaturalist.org/observations/94037750

https://www.inaturalist.org/observations/54885436

https://www.inaturalist.org/observations/67329073

https://www.inaturalist.org/observations/43545138

https://www.inaturalist.org/observations/57490463

The following shows that the whitish on the buttocks can be seen at some distance:
https://www.inaturalist.org/observations/67328340

The following is the only photo of nominate kirkii, in posteriolateral view, that could be confused with damarensis on the basis of the colouration of the hindquarters: https://www.inaturalist.org/observations/104982462.

HINDEI

The following show that considerably more white is visible on the hindquarters than in damarensis. This seems, at least partly, because the pelage of the outer buttock is shorter than that of damarensis.

Whether this qualifies as a buttock flag remains unclear, because this would depend on

• a flaring mechanism (see https://www.inaturalist.org/observations/59156961) that remains to be observed, and/or
• an ultraviolet aspect to the colouration of the pelage.

https://www.inaturalist.org/observations/93574203

https://www.inaturalist.org/observations/106353312

https://www.inaturalist.org/observations/69253350

https://www.inaturalist.org/observations/65705924

https://www.inaturalist.org/observations/104985979

https://www.inaturalist.org/observations/88356487

https://www.inaturalist.org/observations/38088841

https://www.inaturalist.org/observations/49698957

https://www.inaturalist.org/observations/9839405

https://www.inaturalist.org/observations/120567853

https://www.inaturalist.org/observations/106400612

https://www.inaturalist.org/observations/136176636

https://www.inaturalist.org/observations/132019130

https://www.inaturalist.org/observations/106400622

https://www.inaturalist.org/observations/7094056

https://www.inaturalist.org/observations/104985978

https://www.inaturalist.org/observations/103589197

https://www.inaturalist.org/observations/63258767

https://www.inaturalist.org/observations/68337080

The following, at the lower Tana River in eastern Kenya, do not show any white on the buttocks:
https://www.inaturalist.org/observations/8035356
https://www.inaturalist.org/observations/8035355.

CAVENDISHI

The following show that, if white is more evident on the hindquarters of cavendishi than on those of damarensis, the difference is slight.

https://www.inaturalist.org/observations/102103762

https://www.inaturalist.org/observations/121609294

https://www.inaturalist.org/observations/121987458

https://www.inaturalist.org/observations/28289382

https://www.inaturalist.org/observations/130009932

https://www.inaturalist.org/observations/126027728

https://www.alamy.com/dik-dik-at-serengeti-national-park-tanzania-it-is-standing-next-to-a-cabin-at-serengeti-serena-lodge-image229026902.html?imageid=F97CE3DF-A3FE-4CD8-AFAF-78F527703883&p=147085&pn=1&searchId=a091ff7a0a8c31eef18a8931488c16a4&searchtype=0

https://www.inaturalist.org/observations/54027328

https://www.inaturalist.org/observations/108501982

https://www.inaturalist.org/observations/108373392

https://www.alamy.com/kirks-dik-dik-is-a-small-antelope-native-to-eastern-africa-and-one-of-four-species-of-dik-dik-antelope-image348585446.html?imageid=55F02CD5-CE20-4865-8289-4C8CA506FED5&p=432935&pn=2&searchId=812e1b51f3bb17a7cc79ddae25b30690&searchtype=0

https://www.inaturalist.org/observations/107139654

https://www.inaturalist.org/observations/107139648

https://www.inaturalist.org/observations/105392544

https://www.inaturalist.org/observations/103901346

https://www.inaturalist.org/observations/95525881

https://www.inaturalist.org/observations/85640172

https://www.inaturalist.org/observations/68957254

https://www.inaturalist.org/observations/31994682

The following individual shows the maximum extent of whitish on the buttocks:
https://www.inaturalist.org/observations/43172082.

THOMASI

https://www.inaturalist.org/observations/21312691

https://www.inaturalist.org/observations/7812390

https://www.inaturalist.org/observations/764507

https://www.inaturalist.org/observations/61868136

The following does show some white on the buttocks:
https://www.inaturalist.org/observations/15041808.

INTERGRADATIONAL between cavendishi and thomasi, in Tarangire and Lake Manyara National Parks, Tanzania:

https://www.inaturalist.org/observations/19944469
https://www.inaturalist.org/observations/103939955
https://www.inaturalist.org/observations/135088492
https://www.inaturalist.org/observations/1818614
https://www.inaturalist.org/observations/864173
https://www.inaturalist.org/observations/105631501
https://www.inaturalist.org/observations/27609142
https://www.inaturalist.org/observations/104807392
https://www.inaturalist.org/observations/128035858
https://www.inaturalist.org/observations/102033238
https://www.inaturalist.org/observations/97421799
https://www.inaturalist.org/observations/93832001
https://www.inaturalist.org/observations/90118758

The following, in Arusha National Park, look like thomasi rather than hindei:
https://www.inaturalist.org/observations/67200531
https://www.inaturalist.org/observations/8708916.

DAMARENSIS

The following show that the occurrence of whitish on the hindquarters is limited to the inner surface of the upper hindleg, with hardly any sign of any extension on to the buttocks.

https://www.inaturalist.org/observations/41807012

https://www.inaturalist.org/observations/37693539

https://www.inaturalist.org/observations/86033865

https://www.inaturalist.org/observations/99881333

https://www.inaturalist.org/observations/37625508

https://www.inaturalist.org/observations/9704334

https://www.inaturalist.org/observations/52150014

https://www.inaturalist.org/observations/39830600

https://www.inaturalist.org/observations/14293979

https://www.inaturalist.org/observations/128717848

https://www.inaturalist.org/observations/14702761

https://www.inaturalist.org/observations/25626334

https://www.inaturalist.org/observations/33784213

https://www.inaturalist.org/observations/107650742

https://www.inaturalist.org/observations/90441472

https://www.inaturalist.org/observations/85993599

https://www.inaturalist.org/observations/85739109

https://www.inaturalist.org/observations/83787773

https://www.inaturalist.org/observations/33126151

Second photo in https://www.inaturalist.org/observations/74072495

https://www.inaturalist.org/observations/65453512

https://www.inaturalist.org/observations/59859034

tail raised, revealing the black bare skin around anus:
https://www.inaturalist.org/observations/66833293

The following does show some white:
https://www.alamy.com/a-damara-dik-dik-or-kirks-dik-dik-maquoda-kirkii-in-grass-during-the-wet-season-at-erindi-reserve-in-erongo-region-namibia-image367603484.html?imageid=BE2F0F65-D863-4D63-B019-455BE8C48547&p=767630&pn=1&searchId=a091ff7a0a8c31eef18a8931488c16a4&searchtype=0.

Posted on Οκτώβριος 05, 2022 0153 ΠΜ by milewski