The three main types of oribi (Ourebia), at a glance
@tonyrebelo @ludwig_muller @oviscanadensis_connerties @jeremygilmore @beartracker @capracornelius @aguilita @davidbygott @dejong @tandala @michalsloviak @chewitt1 @matthewinabinett @paradoxornithidae @jacqueline_llerena @simontonge @jwidness @mathiasdhaen @bartwursten @henrydelange
(Also see https://www.inaturalist.org/journal/milewski/69937-adaptive-colouration-in-the-oribi-southern-forms-are-more-conspicuous-than-northern-forms# and https://www.inaturalist.org/journal/milewski/70005-are-there-two-species-of-oribi-ourebia-instead-of-one#.)
Dear reader, who among you would assume that the following belong to a single species?
https://www.inaturalist.org/observations/33442601
https://midlandsconservanciesforum.files.wordpress.com/2014/02/oribi.jpg
In explanation of this incongruity, I offer the following summary.
Species/subspecies of genus OUREBIA, on the basis of geographical radiation:
NORTHWESTERN
quadriscopa (plus dorcas, and possibly aequatoria)
sexually dimorphic in both body size and body shape
inconspicuous colouration, with small-scale flags (caudal and pedal)
tail dark brown on upper surface, pale on lower surface
buttocks pale brown, with whitish restricted to narrow bracketing of the tail
https://www.inaturalist.org/observations/49539984
https://www.inaturalist.org/observations/49107482
habitat wooded
NORTHEASTERN
montana (plus gallarum, cottoni, masakensis, and hastata)
sexually dimorphic in both body size and body shape
inconspicuous colouration, with small-scale flags (could and pedal)
tail medium brown on upper surface, pale on lower surface
buttocks pale brown, with whitish almost restricted to narrow bracketing of the tail
https://www.inaturalist.org/observations/32868111 and https://www.natureinstock.com/search/preview/oribi-ourebia-ourebi-murchison-falls-national-park-uganda/0_00127717.html
habitat semi-wooded
SOUTHWESTERN
ourebi (plus rutila)
sexually monomorphic in both body size and body shape
conspicuous colouration overall
tail black on both upper and lower surfaces
buttocks fully white
http://elelur.com/data_images/mammals/oribi/oribi-01.jpg
habitat treeless
Ear pinnae are larger in quadriscopa (https://www.inaturalist.org/observations/46208974) than in ourebi (https://www.inaturalist.org/observations/37228005 and scroll in http://watervalesafaris.com/conservation/oribi-breeding-program/conservation-post/)
The northeastern type barely qualifies for a caudal flag, because there is so little dark/pale contrast on tail/rump/buttocks.
A pedal flag (conspicuously pale pasterns) is present in quadriscopa etc. (https://www.inaturalist.org/observations/8490596) and montana etc. (https://www.alamy.com/oribi-ourebia-ourebi-murchison-falls-national-park-uganda-image239726666.html?imageid=8E7DCBEB-CA6B-4657-BA96-718F12A800C9&p=22059&pn=1&searchId=f7d66f1874b5dfa1e536bf9cbab6379c&searchtype=0 and https://project-zoo.fandom.com/wiki/Oribi?file=Oribi-antelope.jpg), but absent in ourebi etc.
On the basis of the above, I propose that there are two spp. of Ourebia, viz.
- COMMON ORIBI (consisting of the northwestern and northeastern forms, with adaptively inconspicuous colouration), and
- SOUTHERN ORIBI (consisting of the southwestern forms, with adaptively conspicuous colouration).
Comments
https://oribicoza.wixsite.com/oribicoza/identify-an-oribi
The following (https://psnp.info/p4td_/?m=20220913#jp-carousel-15901) clearly shows the inconspicuous colouration of the buttocks in the northeastern type (ssp. cottoni/masakensis in this case).
QUADRISCOPA:
The following (see second photo in https://www.inaturalist.org/observations/36680829) shows that, in some individuals, there is virtually no pale feature on the hindquarters, including the vicinity of the tail, in ssp. quadriscopa.
The following (https://www.inaturalist.org/observations/16068513) shows the (slight) pattern revealed by the sideways displacement of the tail.
Also see https://www.inaturalist.org/observations/16026430.
@milewski Thanks for copying me in with your various posts. You have certainly made a good case that there is something 'wrong' in our current conception of the genus Ourebia. I guess I would just echo @michalsloviak's comments that he made yesterday, about trying to get this work in front of people with the background knowledge, the access to properly referenced museum collections, and the funding to do the necessary genetic work. I don't know any personally, but may know a man who does, and I will certainly draw his attention to it. Anyway, well done for putting together such an interesting set of observations.
@simontonge Many thanks for your encouraging words.
NORTHEASTERN
http://elelur.com/data_images/mammals/oribi/oribi-03.jpg
The following may seem photographically poor. However, they happen to show the difference in adaptive conspicuousness of the hindquarters, at the distance relevant for scanning by predators.
SOUTHERN ORIBI, South Africa:
https://www.inaturalist.org/observations/45171350
COMMON ORIBI, central Mozambique, ostensibly extending to southeastern Zimbabwe, and possibly extending to the latitudes of South Africa in southern Mozambique:
https://www.inaturalist.org/observations/5465647
Ourebia montana cottoni/masakensis:
https://www.alamy.com/a-male-oribi-ourebia-ourebi-grooms-its-back-serengeti-national-park-tanzania-image335366649.html?imageid=1268AFB2-D1CE-45F0-A14C-0F19D2D06532&p=39397&pn=1&searchId=d592d238c126347ec4d3725c2a7bbfc9&searchtype=0
ALSO PLEASE SEE https://www.inaturalist.org/journal/milewski/71348-important-re-oribis-ourebia#.
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