The pronghorn (Antilocapridae: Antilocapra americana) is renowned for its extreme speed and endurance when running (https://www.youtube.com/watch?v=jR18k9c3MsE).
It is widely accepted that no animal on Earth exceeds the pronghorn in this combination.
Skeptical readers may perhaps suspect that the performance of the pronghorn my perhaps have been exaggerated.
However, the claims of speed and endurance are consistent with several other exceptional/extreme features, viz.
All of the above add up to a syndrome of apparent 'hypercursoriality' in the pronghorn.
This syndrome seems incongruous, because the predatory regime in which the pronghorn lives is less, not more, intense than that pertaining to 'plains game' in Africa and Eurasia.
https://www.perplexity.ai/search/Compare-the-maximum-RVcPX3W1Q5GD5EbGMHJ5Vw
The long-range visual vigilance of the pronghorn is indicated partly by fully lateral placement of the eyes on the head, permitting the pronghorn to scan the horizon behind it as well as in front and to the sides.
However, this in itself hardly differs from 'plains game' in Africa and Eurasia.
What distinguishes the pronghorn are
The long-distance signalling of the pronghorn is indicated partly by a conspicuously pale patch on the hindquarters (https://www.flickr.com/photos/189038430@N06/53350736417/in/faves-58287925@N05/ and https://pngtree.com/freebackground/pronghorn-antelope-buck-antlers-hunting-pronghorn-nature-photo_4107882.html).
However, various other forms of 'plains game' have comparable features of colouration.
What is extreme in the case of the pronghorn is
The limited incidence of displays of individual fitness in the pronghorn is not categorically different from various 'plains game' in Africa. For example, Damaliscus spp. tend not to stot, despite being extremely cursorial among Bovidae.
However, what is odd in the case of the pronghorn is that
This raises the question:
Selenium:
https://www.horizons-mag.ch/2017/04/03/the-world-map-of-a-trace-element/
https://drkhorsesense.wordpress.com/2021/03/11/lose-your-fear-of-selenium/
https://poisonousplants.ansci.cornell.edu/toxicagents/selenium_map.html
https://pubs.usgs.gov/publication/70006713
https://customequinenutrition.com/blogs/nutrients/selenium-101
Please see
There are two species of klipspringer, not one.
Oreotragus oreotragus occurs in South Africa (Drakensberg, Karoo, Western Cape, Northern Cape, Namibia as far north as Windhoek).
Oreotragus saltatrixoides occurs in the rest of Africa, including Mpumalanga, Limpopo, and Northwest provinces of South Africa, and northwestern Namibia.
OREOTRAGUS OREOTRAGUS
Orientation of ear pinnae vertical
Pattern on front-of-ear inconspicuous (= not qualifying as an auricular flag)
https://critterfacts.com/klipspringer/?doing_wp_cron=1713667813.4174098968505859375000
https://mostlybirding.files.wordpress.com/2019/01/pick-2018-48.jpg
OREOTRAGUS SALTATRIXOIDES
Orientation of ear pinnae horizontal
Pattern on front-of-ear conspicuous (= qualifying as an auricular flag)
https://www.gettyimages.co.uk/detail/photo/klipspinger-male-royalty-free-image/524447344
https://www.dreamstime.com/klipspringer-oreotragus-brookfield-zoo-illinois-march-image141868490
https://www.dreamstime.com/stock-photo-klipspringer-closeup-portrait-oreotragus-oreotragus-small-african-antelope-image44207213 and https://www.alamy.com/stock-image-klipspringer-oreotragus-oreotragus-or-small-african-antelope-164226024.html
In previous Posts, I have shown that certain species of Cervidae are sexually dimorphic in the colouration of their ears.
More particularly, mature males tend to lack certain conspicuously pale markings at/near the bases of the ear pinnae (https://www.inaturalist.org/posts/69281-intriguing-new-sexual-dimorphism-in-the-wapiti#).
I have hypothesised that the loss of the markings in question, as males grow from juveniles to adults, may be related to the presence of antlers in males only. The showiness of these head-adornments theoretically eclipses any intraspecific communication via the swivelling movements of the ear pinnae.
Some semblance of this kind of sexual dimorphism may also occur in a few Bovidae. I refer particularly to Kobus kob (https://www.inaturalist.org/journal/milewski/91107-adaptive-colouration-in-the-puku-kobus-vardoni-an-anomalously-plain-coloured-grazer-part-1#), which resembles cervids in that horns are restricted to males.
While scrolling through thousands of photos of the pronghorn (Antilocapra americana), I have come to suspect that the colouration of the ear pinnae of this member of the Antilocapridae is sexually dimorphic.
In this case it is dark, not pale, markings that differ. The tips and margins of the ear pinnae tend
The sexual dimorphism of the head adornments in the pronghorn is limited, because
Furthermore, in the pronghorn the ear pinnae have a peculiar shape, suggesting a subtle 'mimicry' of horns. The tips are pointed and turned somewhat medially, which gives an impression of 'bracketing' the horns, in a way.
With the above in mind, I scrutinised the Web for illustrations of this sexual difference. The results are inconclusive, as follows.
Adult females and juveniles:
https://www.featheredphotography.com/blog/2023/05/23/pronghorn-doe-portrait/
https://www.tmurphywild.com/product/pronghorn-antelope-juvenile-head/
https://www.flickr.com/photos/tomblandford/53083685549
https://www.reddit.com/r/wildlifephotography/comments/19180dc/pronghorn_antelope_near_agate_utah/
https://pbase.com/clinton62/image/147356192
https://www.facebook.com/USFWS/photos/a.419357095774/10159745741580775/?type=3
https://www.shutterstock.com/da/image-photo/wild-pronghorn-antelope-doe-south-dakota-2421372029
https://www.shutterstock.com/da/image-photo/antelope-close-bedded-down-meadow-30517435
https://www.agefotostock.com/age/en/details-photo/young-pronghorn-antelope/AAM-AAES61669
https://roadsendnaturalist.files.wordpress.com/2013/06/pronghorn-face.jpg
https://www.istockphoto.com/photo/deer-with-a-grass-straw-gm629027374-111821203
Adult males:
https://mjspringett.com/2013/05/24/pronghorn-2/pronghorn-2/
https://www.featheredphotography.com/blog/wp-content/uploads/2013/08/pronghorn-6378-ron-dudley.jpg
https://www.istockphoto.com/photo/pronghorn-face-gm147091243-7521697
https://www.masterfile.com/image/en/841-06806323/pronghorn-antilocapra-americana-buck-custer-state
https://psmag.com/environment/fracking-away-the-wildlife-44012
https://bestpaintbynumbers.shop/products/close-up-pronghorn-paint-by-numbers/
https://www.shutterstock.com/da/image-photo/pronghorn-antelope-sagebrush-meadow-buck-male-1577197222
https://www.shutterstock.com/da/image-photo/pronghorn-antelope-buck-feeding-on-sagebrush-1872295927
https://www.shutterstock.com/da/image-photo/pronghorn-antelope-morning-495783544
https://www.istockphoto.com/photo/pronghorn-deer-in-montana-gm1189769147-336992051
https://www.istockphoto.com/photo/horned-and-handsome-gm1086413868-291496309
https://www.istockphoto.com/photo/pronghorn-antelope-buck-gm474778752-64903423
https://www.istockphoto.com/photo/pronghorn-gm629792922-112192655
https://www.istockphoto.com/photo/a-stoic-pronghorn-gm833598046-135570567
https://www.onthewingphotography.com/wings/2017/06/22/buck-pronghorn-close-up-on-antelope-island/
@beartracker @maxallen @aguilita @jwidness @matthewinabinett @davidbygott @ptexis @taogirl @variani18
INTRODUCTION
The pronghorn (Antilocapra americana) is renowned for its extreme speed and endurance when galloping - a topic which I do not address in this Post.
Instead, my aim is to illustrate the following, lesser-known gaits of the pronghorn, viz.
The gaits of the pronghorn were well-documented more than 40 years ago (Bullock 1982, https://d1wqtxts1xzle7.cloudfront.net/38898576/Franklin_Vicuna_1974.pdf?1443280555=&response-content-disposition=inline%3B+filename%3DThe_Social_Behavior_of_the_Vicuna_p_477.pdf&Expires=1712873946&Signature=SECkGoREl0a4cUhkekReWb~lmpS6pcXk3a8mKqpPS1NBzaognfNWVSikWAgOp8og4Zg5hKKo7IwBdCpRhQJoFctQfmEmTybFmoOLzO4mw5I6veY5WEbKvheRW6Fs1KwCuTXl-7JONfeN1~hknoodkwwpFlnCA4Jx7k6Z6UzoL~T3CSTtUAgdBOhfXJBPHUTLzjELAzBrYbmWIsfTh3LCiJAjQyeqerYW32CUzD7OQs4nUk-yyMG028rFb-yvfhlYljCstpqVvzsPMc1ppUe1xlbg4xrtVh59t1-H7XDKRYeu-CXvagQt-pDu7aMuBrsYKaQXR0qcAwCElwV6b4jVbg__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA#page=272 and https://cdnsciencepub.com/doi/abs/10.1139/z82-243?journalCode=cjz and https://www.researchgate.net/publication/237992215_An_analysis_of_locomotor_body_movements_in_pronghorn_antelope and https://cdnsciencepub.com/doi/abs/10.1139/z82-243 and https://www.jstor.org/stable/3830497).
However, it is only now that there are enough photos of this species on the Web to illustrate certain gaits clearly. The terms I use do not necessarily correspond to those of Bullock (1982).
RESULTS
Cross-walking:
https://medium.com/usfws/rare-sonoran-pronghorn-are-rebounding-5de9c5343ded
https://www.inaturalist.org/observations/151154169
https://www.inaturalist.org/observations/111103776
https://www.inaturalist.org/observations/192148380
https://www.inaturalist.org/observations/7877948
https://www.inaturalist.org/observations/45872075
https://www.inaturalist.org/observations/45933776
https://www.inaturalist.org/observations/22592549
https://www.inaturalist.org/observations/198888097
https://www.inaturalist.org/observations/67474435
https://www.inaturalist.org/observations/60448113
https://www.inaturalist.org/observations/49918376
https://www.inaturalist.org/observations/14608967
https://www.inaturalist.org/observations/206380030
https://www.inaturalist.org/observations/188952650
https://www.inaturalist.org/observations/136027864
https://www.inaturalist.org/observations/120592993
https://www.inaturalist.org/observations/117610955
https://www.inaturalist.org/observations/112181226
https://www.inaturalist.org/observations/105114626
https://www.inaturalist.org/observations/34874373
https://www.inaturalist.org/observations/27069190
https://www.inaturalist.org/observations/646613
https://www.inaturalist.org/observations/172730233
https://www.inaturalist.org/observations/160784537
https://www.inaturalist.org/observations/86366821
https://www.inaturalist.org/observations/69182943
https://www.inaturalist.org/observations/126642775
https://www.inaturalist.org/observations/168931232
https://www.inaturalist.org/observations/149564088
https://www.inaturalist.org/observations/104441773
https://www.inaturalist.org/observations/72881424
https://www.inaturalist.org/observations/28156962
https://www.inaturalist.org/observations/194604847
https://www.inaturalist.org/observations/189136437
https://www.inaturalist.org/observations/188672871
https://www.inaturalist.org/observations/169802309
https://www.inaturalist.org/observations/169102077
https://www.inaturalist.org/observations/164225148
https://www.inaturalist.org/observations/141591681
https://www.inaturalist.org/observations/128406785
https://www.inaturalist.org/observations/58704010
https://www.inaturalist.org/observations/25524800
https://www.inaturalist.org/observations/369882
https://www.inaturalist.org/observations/198029380
https://www.inaturalist.org/observations/83973812
https://www.inaturalist.org/observations/38435151
https://www.inaturalist.org/observations/19730539
https://www.inaturalist.org/observations/81736547
https://www.inaturalist.org/observations/18340076
https://www.inaturalist.org/observations/13011401
https://www.inaturalist.org/observations/10091257
https://www.inaturalist.org/observations/180569759
https://www.inaturalist.org/observations/162597053
https://www.inaturalist.org/observations/112784916
https://www.inaturalist.org/observations/206481220
https://www.inaturalist.org/observations/167297136
https://www.inaturalist.org/observations/144115273
https://www.inaturalist.org/observations/124978685
https://www.inaturalist.org/observations/202996237
Semi cross-walking:
https://www.storyblocks.com/video/stock/pronghorn-antelope-walking-in-the-plains-hag1g3ixwj2v2c9nu
https://www.storyblocks.com/video/stock/pronghorn-antelope-tracked-while-walking-in-grass-ki1bmav
https://www.inaturalist.org/observations/169977981
https://www.inaturalist.org/observations/81226031
https://www.inaturalist.org/observations/165599558
https://www.inaturalist.org/observations/77144531
https://www.inaturalist.org/observations/108666122
https://www.inaturalist.org/observations/4682916
https://www.inaturalist.org/observations/180187343
https://www.inaturalist.org/observations/141759202
https://www.inaturalist.org/observations/116033559
https://www.inaturalist.org/observations/95166793
https://www.inaturalist.org/observations/190532708
https://www.inaturalist.org/observations/187425583
https://www.inaturalist.org/observations/187403044
https://www.inaturalist.org/observations/164915852
https://www.inaturalist.org/observations/161660531
https://www.inaturalist.org/observations/120618226
https://www.inaturalist.org/observations/112788711
https://www.inaturalist.org/observations/45924357
https://www.inaturalist.org/observations/37510543
https://www.inaturalist.org/observations/7975933
https://www.inaturalist.org/observations/173803819
https://www.inaturalist.org/observations/192932980
https://www.inaturalist.org/observations/24766943
https://www.inaturalist.org/observations/2313666
https://www.inaturalist.org/observations/202605521
https://www.inaturalist.org/observations/105126822
https://www.inaturalist.org/observations/16640889
https://www.inaturalist.org/observations/181843893 and https://www.inaturalist.org/observations/179269836
https://www.inaturalist.org/observations/181284223
https://www.inaturalist.org/observations/176878956
https://www.inaturalist.org/observations/172456278
https://www.inaturalist.org/observations/138443166
https://www.inaturalist.org/observations/135297540
https://www.inaturalist.org/observations/130235159
https://www.inaturalist.org/observations/123661093
https://www.inaturalist.org/observations/92061482
https://www.inaturalist.org/observations/90601957
https://www.inaturalist.org/observations/27175238
https://www.inaturalist.org/observations/25857516
https://www.inaturalist.org/observations/19058413
https://www.inaturalist.org/observations/12998710
https://www.inaturalist.org/observations/199628
https://www.inaturalist.org/observations/159245812
https://www.inaturalist.org/observations/192495811
https://www.inaturalist.org/observations/173367219
https://www.inaturalist.org/observations/124848728
https://www.inaturalist.org/observations/124652556
https://www.inaturalist.org/observations/105552317
https://www.inaturalist.org/observations/90042028
https://www.inaturalist.org/observations/77808716
https://www.inaturalist.org/observations/71174311
https://www.inaturalist.org/observations/66697932
https://www.inaturalist.org/observations/19299335
https://www.inaturalist.org/observations/1434006
https://www.inaturalist.org/observations/192755246
https://www.inaturalist.org/observations/184207314
https://www.inaturalist.org/observations/181446232
https://www.inaturalist.org/observations/170446653
https://www.inaturalist.org/observations/168856780
https://www.inaturalist.org/observations/153092774
https://www.inaturalist.org/observations/123618854
https://www.inaturalist.org/observations/116494036
https://www.inaturalist.org/observations/71882182
https://www.inaturalist.org/observations/62759588
https://www.inaturalist.org/observations/57729297
https://www.inaturalist.org/observations/39740119
https://www.inaturalist.org/observations/8697208
https://www.inaturalist.org/observations/178173951
https://www.inaturalist.org/observations/165313189
https://www.inaturalist.org/observations/40796530
https://www.inaturalist.org/observations/5173255
https://www.inaturalist.org/observations/200516676
https://www.inaturalist.org/observations/131997891
https://www.inaturalist.org/observations/128984894
https://www.inaturalist.org/observations/128984893
https://www.inaturalist.org/observations/108361908
https://www.inaturalist.org/observations/60921261
https://www.inaturalist.org/observations/28039844
https://www.inaturalist.org/observations/6186244
https://www.inaturalist.org/observations/171266598
https://www.inaturalist.org/observations/125877305
https://www.inaturalist.org/observations/116925430
https://www.inaturalist.org/observations/104078696
https://www.inaturalist.org/observations/62604018
https://www.inaturalist.org/observations/38034079
Ambling:
https://blog.gritrsports.com/big-game-profile-pronghorn/
https://www.oceanlight.com/spotlight.php?img=19627
https://www.inaturalist.org/observations/74202062
https://www.inaturalist.org/observations/172746714
https://www.inaturalist.org/observations/41200343
https://www.inaturalist.org/observations/60531788
https://www.inaturalist.org/observations/5119706
https://www.inaturalist.org/observations/38203216
https://www.inaturalist.org/observations/89398530
https://www.inaturalist.org/observations/26399635
https://www.inaturalist.org/observations/161080559
https://www.inaturalist.org/observations/137670731
https://www.inaturalist.org/observations/197367318
https://www.inaturalist.org/observations/137336427
https://www.inaturalist.org/observations/193225312
https://www.inaturalist.org/observations/153326755
https://www.inaturalist.org/observations/14970879
https://www.inaturalist.org/observations/160981894
https://www.inaturalist.org/observations/143827822
https://www.inaturalist.org/observations/165313190
https://www.inaturalist.org/observations/143377354
https://www.alamy.com/video/pronghorn-walking-in-a-field-582837040.html
https://www.inaturalist.org/observations/75666276
Proud-trotting:
https://www.inaturalist.org/observations/162332610
https://www.inaturalist.org/observations/6506049
https://www.inaturalist.org/observations/119916340
https://www.inaturalist.org/observations/28842659
https://www.inaturalist.org/observations/10151399
https://www.inaturalist.org/observations/196884072
https://www.inaturalist.org/observations/153327177
https://www.inaturalist.org/observations/142944555
https://www.inaturalist.org/observations/65214769
https://www.youtube.com/watch?v=58bODe6e7gA
Stotting:
Scroll in https://content.govdelivery.com/accounts/USDOI/bulletins/3478106
https://blissphotographics.com/pronking-pronghorn-levitating/
https://blissphotographics.com/pronghorn-levitation-stotting-or-pronking/
https://www.pinterest.com.au/pin/graceful-pronghorn-in-midair--320529698481685013/
https://www.inaturalist.org/observations/99162488
https://www.inaturalist.org/observations/26690567
https://www.inaturalist.org/observations/153327177
https://www.inaturalist.org/observations/20058575
https://www.inaturalist.org/observations/81342377
https://www.inaturalist.org/observations/18212065
https://www.inaturalist.org/observations/5028581
DISCUSSION
The pronghorn conforms to a category of ungulates that I have called 'plains game'.
This is because it combines the following features/traits:
Species of 'plains game' in the family Bovidae, in Africa and Eurasia, typically amble. I refer to all Alcelaphini and Hippotagini, and certain Antilopini, Reduncini, and possibly Caprini.
Based on its evolutionary convergences with 'plains game', we would expect the pronghorn to amble.
However, Bullock (1982) - despite the thoroughness of his study - did not find the pronghorn to amble.
So, is it true that the pronghorn is anomalous relative to bovid 'plains game', in lacking an ambling gait?
My study, as illustrated in this Post, offers a correction to Bullock (1982). In fact, the pronghorn does sometimes amble.
The pronghorn is partly aligned with Cervidae, a family in which ambling is absent in even those species
The following (https://www.inaturalist.org/observations/133255783 and https://www.youtube.com/watch?v=V8-1p8WhAYo and https://www.youtube.com/watch?v=r72AnyDaxS0) show the cross-walk typical of Cervidae.
On this basis, it would seem that the pronghorn incongruously combines cross-walking with extreme speed and endurance of galloping.
The diagnostic pattern of 'diagonal' walking gaits - including the cross-walk of the pronghorn - is that the hind foot lifts only once the contralateral foot lands, and the hind foot lands approximately in the track of the ipsilateral fore foot (https://www.inaturalist.org/observations/40017869 and https://www.inaturalist.org/observations/65114417 and https://www.inaturalist.org/observations/204861686 and https://www.inaturalist.org/observations/167405274 and https://www.inaturalist.org/observations/18491683).
Bullock (1982) documented that the pronghorn varies this in two ways, viz.
However, Bullock (1982) failed to document the full versatility of walking gaits in the pronghorn.
The following (https://www.inaturalist.org/observations/126912485) shows this versatility. The juvenile individual on the left is cross-walking, while that on the right is ambling.
In the case of 'display gaits', there is also something new to be investigated about the pronghorn. This is the possibility of two 'display gaits' additional to stotting (in the narrow sense).
These are
However, I have found few unambivalent illustrations of stotting/display gaits in the pronghorn, in either the strict or the loose sense. According to Bullock (1982), stotting is mainly an intraspecific (as opposed to anti-predator) display in the pronghorn, and observed mainly in the breeding season. However, this remains poorly documented photographically.
It is remarkable that infants seem not to stot during play behaviour (https://www.youtube.com/watch?v=ZwE_IFvABKw and https://www.youtube.com/watch?v=NQdzJm0A5co).
The pronghorn is extreme, among ungulates, in advertising itself by means of piloerection of the white bleeze on the hindquarters (https://www.inaturalist.org/observations/17052354 and https://www.inaturalist.org/observations/144032230 and https://www.inaturalist.org/observations/124828985).
However, any correlation between gait and the piloerection of this acetabulo-ischiopygal bleeze - which often occurs when the figure is stationary - is weak.
MAIN QUESTIONS RAISED
This investigation has raised three main questions about the gaits of the pronghorn, as follows. In this species,
Also see
It is widely known that the walking gait of giraffes (Giraffa) is unusual (https://www.researchgate.net/figure/Categorisation-of-giraffes-walking-gait-Reproduction-of-Hildebrands-plot-for_fig3_329382181 and https://academic.oup.com/jmammal/article-abstract/41/2/282/933378?redirectedFrom=PDF&login=false).
However, like many 'factoids' about Nature, this is subject to context.
It is true that giraffes have a 'parallel', not a 'diagonal', stride while walking (https://www.youtube.com/watch?v=n9redgIffu4 and https://www.youtube.com/watch?v=FBz1rQ5z8uE and https://www.facebook.com/watch/?v=1723826704314545and https://www.youtube.com/watch?v=Vh2yveXTKaU and https://www.youtube.com/watch?v=o9TuZCG1f0k).
However, the same is true also for many Carnivora.
The lion (Panthera leo), walking behind its intended prey, a giraffe, uses the same 'parallel' stride (https://www.youtube.com/watch?v=o9TuZCG1f0k and https://www.youtube.com/watch?v=-QnyACx936I and https://stock.adobe.com/images/big-lion-walking-shot-in-profile/210044363 and https://www.africanreferencephotos.com/photo/2209/Profile-of-Male-Lion-Walking.html).
And, in turn, the lion walks similarly to the brown bear (Ursus arctos, https://stock.adobe.com/search?k=bear+walking&asset_id=298297872 and https://stock.adobe.com/search?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=bear+walking&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=129616916).
(Yes, it is true that the brown bear walks like a giraffe, in the sense that the hind foot lifts only once the opposite fore foot has landed, and the hind foot lands (i.e. 'oversteps') considerably anterior to the print of the fore foot on the same side.)
Why is it, then, that this 'parallel' stride is seen as remarkable in giraffes, but not in Carnivora - including the domestic dog (Canis familiaris, https://www.youtube.com/watch?v=eqBcBsmMQVA)?
The obvious answer is:
because a gait that is normal in a plantigrade (e.g. brown bear) and digitigrade (e.g. lion) mammal seems much odder in mammals (giraffes) that are not only unguligrade, but extremely long-legged even among ungulates.
The above framing may explain, at least partly, why giraffes have a reputation for walking in an odd way.
For it is indeed remarkable that, in going from a 'flat-footed' animal, such as a bear, to an animal with 'stilts' for legs, such as a giraffe, the same gait is retained.
However, if this was a complete explanation, then all other hoofed mammals, including those with relatively short legs, would also walk like giraffes and Carnivora.
And this far from being true.
In fact, most ruminants walk in a different way, using a 'diagonal' stride. This applies to all deer (Cervidae, https://www.inaturalist.org/journal/milewski/91548-walking-gaits-in-cervidae-deer-tend-to-cross-walk-as-opposed-to-the-ambling-typical-of-many-bovids-part-1#) and many bovids (Bovidae, https://www.inaturalist.org/posts/85349-gaits-and-other-aspects-of-locomotion-in-hippotragin-bovids#).
Consider the tiger (Panthera tigris) following the sambar deer (Rusa unicolor) (https://www.naturepl.com/stock-photo-bengal-tiger-nature-image01234681.html and https://www.facebook.com/watch/?v=282670022702595 and https://www.youtube.com/watch?v=qX7oEFWuV2I).
The predator uses a 'parallel' stride (https://www.youtube.com/watch?v=MIBAT6BGE6U and https://www.youtube.com/watch?v=6fhAzkK_s_Y), whereas the prey uses a 'diagonal' stride (https://videohive.net/item/beautiful-male-sambar-rusa-unicolor-deer-walking-in-the-forest-of-ranthambore-national-park/25553355 and https://www.shutterstock.com/da/video/clip-1086299906-medium-shot-alert-male-sambar-deer-rusa and https://www.shutterstock.com/da/video/clip-1104756293-sambar-deer-rusa-unicolor-walking-carefully-dense).
One explanation for this anomaly is as follows.
Unguligrady is an adaptation mainly for rapid and enduring fleeing from predators. In the 'arms-race' between prey and predator, hoofed mammals have compensated for the disadvantage of being surprised by predators, by having more efficient sprinting than that of Carnivora.
However, all benefits are accompanied by certain costs. And in the case of ruminants, a cost of 'living on stilts' (= unguligrady) is the risk of instability while walking.
Ruminants compensate for this risk by tending to use diagonal patterns in their walking strides.
This allows deer, for example,
It is only in two categories of ruminants that all 'diagonality' seems to have been abandoned while walking.
These are
'Plains game' artiodactyls emphasise efficiency of walking over stability of walking. This is, hypothetically, why they use a 'parallel' stride, rather than a 'diagonal stride (https://www.youtube.com/watch?v=0WcG532I4is and https://www.google.com.au/search?sca_esv=361d108b9e725553&sxsrf=ACQVn0_rxEkkCe56q3nf8k8XrPxMiTH8Hw:1712749994086&q=Wildebeest+walking+video&tbm=vid&source=lnms&prmd=visnmbtz&sa=X&ved=2ahUKEwi_vPH3yreFAxUrVmwGHb1bClcQ0pQJegQIDBAB&biw=1004&bih=549&dpr=2.7#fpstate=ive&vld=cid:2130b2ac,vid:-_if9UL39Lc,st:0). Their walking gaits are like that of giraffes, but for different reasons.
So, where do impalas fit into this conceptual framework?
Well, impalas walk like giraffes (https://www.inaturalist.org/posts/49366-locomotory-and-postural-peculiarities-of-impalas-aepyceros-part-1#activity_comment_b2dbc656-b062-4be7-9b31-eb6fdd6dc640).
This can perhaps best be explained by comparing impalas with alcelaphin bovids (Alcelaphini).
Alcelaphins (wildebeests, hartebeests, and damalisks) epitomise 'plains game'. They are odd among ruminants in their combination of
It is as part of the above syndrome that the 'parallel' stride of alcelaphins, when walking, can be considered. Alcelaphins are locomotorily aberrant, as part of an extreme relationship to predation.
For their part, impalas are odd among ruminants in their combination of
We can, in light of the above, think of impalas as 'plains game adapted to relatively dense vegetation' (https://www.inaturalist.org/journal/milewski/89704-can-precociality-in-the-colouration-of-impalas-aepyceros-be-explained-by-their-confusing-nature-as-sedentary-plains-game-part-1#).
This would place them - albeit with some 'sheohorning' - into the third category above, namely 'plains game'.
And this leads us to realise something shared by all the ruminants that use 'parallel' - as opposed to 'diagonal' - strides while walking, namely an inability/reluctance to use the ordinary running method known as trotting (https://www.inaturalist.org/posts/49366-locomotory-and-postural-peculiarities-of-the-impala-part-1#).
A trot is a 'diagonal' way of running. It is a standard gait in Carnivora and ungulates.
However, it is
All of these ruminants have - in their own ways and for different reasons - abandoned trotting, as a gait for fleeing and commuting. It is in light of this common denominator that their adoption of a 'parallel' stride, when walking, can be appreciated.
What, then, should we call the 'parallel' gait used by giraffes, camels, 'plains game', and impalas alike?
I suggest that the best term is 'an amble'.
(This is not to be confused with a pace, which is also uses 'parallel' strides, but is a running gait, not a walking one.)
And this means that - to everyone's surprise - impalas and giraffes are evolutionarily convergent in ambling while walking (https://www.youtube.com/watch?v=K24qSp49HHg and https://www.youtube.com/watch?v=4jeoFaKDb70).
This is despite the obvious differences between impalas and giraffes in
Furthermore, any preoccupation that giraffes walk oddly - which remains true in its way but is easily misinterpreted - may now have been overtaken. The more current notion - given the ordinariness of their body-proportions - should be that impalas walk even more oddly.
And this invites the next step in my investigative stroll, as follows.
Warthogs (Phacochoerus) - equally surprisingly - seem to amble (https://www.inaturalist.org/posts/85161-variation-in-walking-gaits-in-ungulates-part-1-why-some-hoofed-mammals-cross-walk-whereas-others-amble#activity_comment_1c97f582-aac3-4d6d-b15f-c533aaba47b5).
This is in keeping with impalas inasmuch as these aberrant suids are 'plains game'. However, the new complication is that warthogs have certainly retained a trotting gait...
Please also see
The Rocky Mountain mule deer (Odocoileus hemionus hemionus) is well-known to have a conspicuous pattern of colouration on the hindquarters.
This is most noticeable in the winter pelage, and in posteriolateral view (https://www.inaturalist.org/observations/97295280 and https://www.inaturalist.org/observations/72504627 and https://www.inaturalist.org/observations/68344771 and https://www.inaturalist.org/observations/61732504).
However, what also requires description and explanation is a conspicuous pattern on the forequarters, which is most noticeable in profile and in a posture in which the inner foreleg is exposed.
The feature in question is complex, consisting of
In having a conspicuously pale inner surface, the foreleg differs from the hindleg (https://www.inaturalist.org/observations/36167595).
In this and other ways, the pattern makes little sense in terms of countershading (https://en.wikipedia.org/wiki/Countershading).
https://www.inaturalist.org/observations/101206028 and https://www.inaturalist.org/observations/101171620
https://www.inaturalist.org/observations/97075871
https://www.inaturalist.org/observations/75142350
https://www.inaturalist.org/observations/69512342
https://www.inaturalist.org/observations/68901309
https://www.inaturalist.org/observations/54358694
https://www.inaturalist.org/observations/52417150
https://www.inaturalist.org/observations/51659800
https://www.inaturalist.org/observations/16922321
https://www.inaturalist.org/observations/10708031
https://www.inaturalist.org/observations/4126822
https://www.inaturalist.org/observations/3213126
https://www.inaturalist.org/observations/205313614 and https://www.inaturalist.org/observations/205313616 and https://www.inaturalist.org/observations/205313613
There is a white patch on the hindquarters of Capreolus, in winter pelage.
This constitutes a flag if unexpanded (https://www.inaturalist.org/observations/200496200).
The same feature constitutes a bleeze if expanded.
This is a difference of scale, effected by complex piloerection.
This piloerection occurs sometimes when the figure is stationary, and sometimes when the figure is fleeing.
Then feature in question can be called ischioperineal, because it is located on the buttocks and the perineum, which connects the left and right buttocks.
unexpanded, constituting an ischioperineal flag:
https://www.inaturalist.org/observations/196664785
https://www.inaturalist.org/observations/200990145
https://www.inaturalist.org/observations/201069507
https://www.inaturalist.org/observations/202679662
https://www.inaturalist.org/observations/202192789
expanded, constituting an ischioperineal bleeze:
https://www.inaturalist.org/observations/197850307
https://www.inaturalist.org/observations/203074169
https://www.inaturalist.org/observations/202864456
expanded or not, according to individual:
https://www.inaturalist.org/observations/200720752
https://www.inaturalist.org/observations/201122384
@matthewinabinett @jeremygilmore @tonyrebelo @variani18 @christiaan_viljoen @paradoxornithidae @beartracker @chewitt1 @gareth_bain
Please also see the following
INTRODUCTION
A cross-walk is a diagonal walking gait, in which left fore tends to move together with right hind, and right fore tends to move together with left hind.
Among ungulates, a 'perfect' example is Hippopotamus amphibius (https://www.pond5.com/stock-footage/item/56467947-hippo-walking-isolated-hippopotamus-video-includes-alpha-cha).
Cross-walking occurs in certain small (body mass less than 35 kilograms) ruminants. More particularly, I refer to cover-dependent, nocturnal, solitary species with inconspicuous colouration (https://www.inaturalist.org/journal/milewski/91630-walking-gaits-in-cervidae-deer-tend-to-cross-walk-as-opposed-to-the-ambling-typical-of-many-bovids-part-2-odocoileinae#).
However, a naturalist can observe these ruminants attentively without noticing that the gait is a cross-walk.
Furthermore, baboons (Papio spp.), macaques (Macaca spp.), and the proboscis monkey (Nasalis larvatus) - all of which habitually cross-walk on the ground - seem to have yet another different action (https://www.gettyimages.com.au/detail/photo/proboscis-monkey-walking-through-mangrove-royalty-free-image/527127928?phrase=proboscis+monkey&adppopup=true and https://www.gettyimages.com.au/detail/photo/proboscis-monkey-walking-through-mangrove-swamp-royalty-free-image/114995835?phrase=proboscis+monkey&adppopup=true).
However, here again, the gait is a cross-walk.
So, how can these disparate impressions be reconciled?
A NOTE ON TECHNICAL TERMS
A problem in studying gaits is confusion of terms.
What I call a cross-walk is alternatively called a 'walking trot' or 'diagonal-sequence walk' (https://onlinelibrary.wiley.com/doi/abs/10.1002/ajpa.1330260203#:~:text=Diagonal%2Dsequence%20gaits%20have%20the,opposite%20side%20of%20the%20body).
'Diagonal-couplets gaits' (see the reference above) include both a running gait (trot) and a walking gait (which I call a cross-walk).
What I call an amble is alternatively called a 'walking pace' or 'lateral-sequence walk'. In my terminology, just as a trot is the running version of a cross-walk, so a pace is the running version of an amble.
I have invented the term 'semi cross-walk' because
AIMS
The aim of this Post is to explain why the walking gaits seem so different in ruminants and monkeys that it took me decades to realise that both kinds of mammals cross-walk.
RESULTS AND DISCUSSION
Please compare
Which reader would have known that all of these photos illustrate cross-walking?
There are six main reasons why cross-walking in ruminants and monkeys seems to consist of categorically different gaits.
These are as follows.
In the ruminants,
Part of the reason why ruminants and monkeys deviate, in opposite directions, from the synchronous placement of the diagonally-opposite feet may be
In the ruminants in question, the rump is higher than the withers (https://www.inaturalist.org/observations/83544190). This is part of a 'hunched' conformation in which - presumably to boost acceleration when predators pounce - the hind legs are longer and springier than the fore legs.
In the monkeys in question, the rump tends to be lower than the withers (https://es.123rf.com/photo_126109982_a-monkey-walking-in-the-street-on-the-sunny-day.html).
This is because
Both the ruminants and the monkeys deviate from Hippopotamus amphibius, in which fore and hind legs are similar in length (https://www.shutterstock.com/image-photo/rare-sighting-hippo-walking-out-water-60570064).
Therefore,
Finally, two relevant differences between the ruminants and the monkeys are that