Adaptive colouration in the puku (Kobus vardoni), an anomalously plain-coloured grazer, part 2

...continued from https://www.inaturalist.org/journal/milewski/91107-adaptive-colouration-in-the-puku-kobus-vardoni-an-anomalously-plain-coloured-grazer-part-1#

INCONSPICUOUS PATTERNS (cont.)

Incipient/residual band at junction of belly/lower flank

This feature, although faint, is consistent among individuals, regardless of sex and age.

https://www.inaturalist.org/observations/37703217

https://www.inaturalist.org/observations/35174260

https://www.inaturalist.org/observations/183532379

https://www.alamy.com/puku-kobus-vardonii-in-south-luangwa-national-park-zambia-puku-south-luangwa-national-park-zambia-image554646007.html?imageid=400C7F4A-C4FC-4712-8446-982514BD414B&p=2184918&pn=1&searchId=660be775941111ad3ff09a1a1eb9c3a4&searchtype=0

https://www.shutterstock.com/image-photo/wildlife-chobe-national-park-botswana-2222434941

https://www.shutterstock.com/image-photo/puku-kobus-vardonii-senganus-male-standing-1624748146

https://www.shutterstock.com/image-photo/male-puku-walking-south-luangwa-2420659305

https://www.shutterstock.com/image-photo/male-puku-154457786

https://www.alamy.com/stock-photo-puku-kobus-vardonii-weibchen-und-jungtier-south-luangwa-national-park-107698960.html?imageid=DEACA7BA-3104-41F5-9F48-5333C521C15C&p=205512&pn=1&searchId=660be775941111ad3ff09a1a1eb9c3a4&searchtype=0

Pale on ventral/anterior surface of neck

https://www.alamy.com/pukus-kobus-vardonii-in-south-luangwa-national-park-zambia-pukus-south-luangwa-national-park-zambia-image554645884.html?imageid=70DB440A-4BA2-4A2A-9C83-4AA4775EDD6D&p=2184918&pn=1&searchId=660be775941111ad3ff09a1a1eb9c3a4&searchtype=0

White on inner surface of upper hindleg

https://www.alamy.com/stock-photo-female-puku-kobus-yardonii-walking-31832363.html?imageid=905185DD-F0A5-4B72-8489-BBF2792AFDF8&p=34420&pn=1&searchId=660be775941111ad3ff09a1a1eb9c3a4&searchtype=0

https://www.shutterstock.com/video/clip-8387497-african-elephants-walking-past-pukus

Plainness on anterior surfaces of legs

https://www.shutterstock.com/image-photo/male-puku-158764706

https://www.shutterstock.com/image-photo/puku-antelope-south-luangwa-national-park-350486321

COMPARISON WITH KOBUS KOB

Nominate subspecies Kobus kob kob

The puku and Kobus kob constitute a 'superspecies', distributed from Senegal to Ethiopia and southwards to Botswana (https://upload.wikimedia.org/wikipedia/commons/8/81/Kobus_kob_distribution.svg and https://upload.wikimedia.org/wikipedia/commons/a/a6/Leefgebied_Puku-Kobus_vardonii.png).

I have shown the colouration of the subspecies Kobus kob kob (https://www.inaturalist.org/journal/milewski/90862-kobus-kob-kob-as-the-west-and-central-african-counterpart-for-the-common-impala-aepyceros-melampus-part-1#).

Comparison with K. k. kob highlights the puzzle of plain colouration in the puku. This is because the former is the smaller-bodied and less associated with open vegetation, yet possesses the more conspicuous features in the form of

• dark on the anterior surfaces of the legs,
• dark on the tail-tassel, and dark on the fetlocks (constituting a pedal flag).

Of the conspicuous features seen in K. k. kob, the only one retained in the puku is the posterior auricular flag.

Subspecies Kobus kob thomasi

The following photo-pair shows that the puku is a dull-coloured version of the Uganda kob (particularly superciliary whitish, and dark on anterior surfaces of legs):
https://www.alamy.com/stock-photo-uganda-kob-kobus-kob-thomasi-23820043.html?imageid=B51D937E-CF43-4818-8D6A-3F9904633452&p=4071&pn=1&searchId=bf0df45f6cdd487771c0a27ea33653bf&searchtype=0
versus
https://www.gettyimages.co.uk/detail/photo/puku-luangwa-national-park-zambia-habitat-is-royalty-free-image/128122833?phrase=puku+kobus+vardonii&adppopup=true and https://www.alamy.com/impala-antelope-at-murchison-falls-national-park-safari-reserve-in-uganda-the-pearl-of-africa-image222662810.html?imageid=1F4848EE-8015-4423-A54C-763925F1ECD2&p=370223&pn=1&searchId=4206b8d7157b1538d730f9c70124285d&searchtype=0 and https://www.alamy.com/puku-kobus-vardonii-standing-side-profile-zambia-image179830705.html?imageid=1B0FF3CF-E751-4143-8839-8165628469EA&p=524999&pn=1&searchId=acc709c179443e5d1df94979b0f1c3a2&searchtype=0

https://www.alamy.com/impala-antelope-at-murchison-falls-national-park-safari-reserve-in-uganda-the-pearl-of-africa-image222662790.html?imageid=2F624F51-ECFF-4EBD-870A-6DE913DE0A75&p=370223&pn=1&searchId=4206b8d7157b1538d730f9c70124285d&searchtype=0

Darkness on the tail-tassel is also less well-developed than in the Uganda kob.

https://www.shutterstock.com/image-photo/uganda-kob-muchison-falls-national-park-1533550322

https://www.shutterstock.com/image-photo/some-uganda-kobs-walking-through-green-87766975

https://www.shutterstock.com/image-photo/baby-kob-his-mother-kobus-murchison-1687419769

https://www.shutterstock.com/image-photo/uganda-kob-kobus-thomasi-national-parks-2083558879

https://www.shutterstock.com/image-photo/ugandan-kob-kobus-thomasi-rainy-day-2103703763

https://www.shutterstock.com/image-photo/uganda-kob-kobus-thomasi-national-parks-2015207261

https://www.shutterstock.com/image-photo/beautiful-uganda-kob-front-centre-jackson-1897215655

DISCUSSION

There are various residual/incipient features in the colouration of the puku. These are noteworthy in assessing relationships between the puku and

• other members of genus Kobus,
• reduncins (including Redunca),
• other gregarious bovids, and
• gregarious cervids in summer pelage.

However, none if these qualifies unambivalently as a conspicuous feature, according to the system of bleezes, flags, and semets ().

The only feature that may perhaps qualify is the pattern on the back-of-ear, consisting of

• an individually variable dark apex, and
• a pale (probably sheeny) ventral panel on the proximal part of the posterior surface of the ear pinna.

The dark apex resembles that (https://www.superstock.com/asset/rear-view-impala-female-head-aepyceros-melampus-nakuru-national-park/1566-1419927) of the common impala (Aepyceros melampus), but is

• not as clear and consistent, and
• somewhat sexually dimorphic, as opposed to monomorphic in the common impala.

The following exceptionally fortunate photo (https://www.gettyimages.co.uk/detail/photo/pukus-impalas-royalty-free-image/560130395?phrase=puku+kobus+vardonii&adppopup=true) shows clearly the evolutionary convergence in the posterior auricular flags of the puku and the common impala.

The pale panel resembles - but is less well-developed than - those in various cervids, e.g. the sika deer (https://www.istockphoto.com/photo/rear-view-of-a-sika-deer-resting-in-an-animal-farm-gm1729392605-541626097?searchscope=image%2Cfilm and https://www.istockphoto.com/photo/close-up-of-fallow-deer-head-gm498401388-79628877?phrase=axis+deer+deer+close+up+macro&searchscope=image%2Cfilm and https://www.dreamstime.com/close-up-head-female-deer-garden-close-up-head-female-deer-garden-image288507716).

The partial loss of the dark/pale contrast on the back-of-ear in mature males is consistent with similarly subtle sexual dimorphism in

• a closely-related congener in the form of Kobus kob thomasi (https://www.alamy.com/stock-image-male-uganda-kob-in-the-mating-ground-murchison-falls-national-park-163136469.html?imageid=F9982B0E-06BC-4A0A-8930-4CCA61C74E5B&p=141869&pn=4&searchId=d179b29ae52b90cc3e3f784ad42733e9&searchtype=0), and
• unrelated forms in a different family, e.g. the wapiti (https://www.inaturalist.org/posts/55532-previously-overlooked-facial-expressions-in-the-wapiti#).

The maximum case for conspicuousness of the pattern on the hindquarters can be seen in https://tandemstock.com/assets/63532549.

The inconspicuousness of the tail of the puku is consistent with that in all other reduncins.

The tail in genus Kobus is possibly less conspicuous than in any other genus of gregarious bovids.

The incipient/residual band at the junction of belly and lower flanks seems convergent with a feature in e.g.

• the Svalbard reindeer (Rangifer tarandus platyrhynchus, https://www.gettyimages.com.au/detail/news-photo/svalbard-reindeer-in-van-mijenfjorden-np-an-endemic-news-photo/1749532742?adppopup=true and https://www.mindenpictures.com/stock-photo-svalbard-reindeer-rangifer-tarandus-platyrhynchus-male-spitsbergen-naturephotography-image00555746.html and https://www.flickr.com/photos/91429690@N03/8300115241 and https://www.agefotostock.com/age/en/details-photo/svalbard-reindeer-rangifer-tarandus-platyrhynchus-bull-walking-in-snow-shedding-its-antlers-svalbard/SSJ-h-81087251 and https://www.gettyimages.com.au/detail/photo/svalbard-reindeer-royalty-free-image/1177589438?phrase=svalbard+reindeer&adppopup=true), and
• the Nubian ibex (Capra ibex, https://es.123rf.com/photo_188992913_vista-invernal-de-la-cabra-mont%C3%A9s-nubia-en-el-valle-del-desierto-de-arava-cerca-del-ca%C3%B1%C3%B3n-shkhoret.html)

This feature, however faint, is puzzling because it seems to undermine the countershading (https://en.wikipedia.org/wiki/Countershading) that is part of cryptic colouration (https://www.alamy.com/stock-photo/female-puku.html?sortBy=relevant and https://www.shutterstock.com/image-photo/solitary-male-puku-antelope-kobus-vardonii-1085192054).

Therefore, the adaptive significance of the darkish belly/flank-band - whether dark in other ruminants or faint as in the puku - remains to be explained.

The puku has lost the pedal flag seen in Kobus kob (https://www.alamy.com/impala-antelope-at-murchison-falls-national-park-safari-reserve-in-uganda-the-pearl-of-africa-image222662810.html?imageid=1F4848EE-8015-4423-A54C-763925F1ECD2&p=370223&pn=1&searchId=bf0df45f6cdd487771c0a27ea33653bf&searchtype=0).

Posted on March 21, 2024 02:45 AM by milewski