milewski's Journal

Muntjaks (Cervidae: Muntiacus) occur in southern and East Asia. They are comparable with duikers (Bovidae: Cephalophus), which occur in Africa.

https://www.inaturalist.org/observations/51907267

Muntiacus feae
https://www.dreamstime.com/stock-photo-fea-muntjac-deer-s-tenasserim-muntiacus-feae-rare-species-native-to-china-laos-myanmar-thailand-image51955354 and https://www.dreamstime.com/stock-photo-fea-muntjac-deer-s-tenasserim-muntiacus-feae-rare-species-native-to-china-laos-myanmar-thailand-image51955105

Muntiacus reevesi
https://www.dreamstime.com/stunning-stag-muntjac-deer-muntiacus-reevesi-feeding-edge-woodland-beautiful-stag-muntjac-deer-muntiacus-reevesi-image139600368

Muntiacus vaginalis
https://www.dreamstime.com/southern-red-muntjac-crossing-path-forest-kaziranga-deer-species-native-to-south-asia-southern-red-image286131596

However, there is a categorical difference between muntjaks and duikers, w.r.t. caudal flagging.

In muntjaks, the tail is relatively large, with white pelage on its ventral side (https://www.inaturalist.org/observations/41672710 and https://www.alamy.com/stock-photo-muntjac-deer-muntiacus-reevesi-tail-uplifted-visual-signal-of-apprehension-27334104.html).

The white extends variably around the perineum and on to the inner surface of the upper hind legs (https://www.inaturalist.org/observations/196475597 and https://www.dreamstime.com/side-profile-barking-deer-muntjac-indian-muntjac-red-muntjac-muntiacus-muntjak-antler-winter-season-evening-image290333571).

The white surface is starkly displayed by erecting the tail.

Muntiacus reevesi (https://www.dreamstime.com/stock-photo-chinese-muntjac-muntiacus-reevesi-also-known-as-reeves-s-wildlife-animal-image56542499 and https://newforestguide.uk/biodiversity/new-forest-deer/muntjac-deer/):

displayed when fleeing

https://www.alamy.com/stock-photo-muntjac-deer-running-away-showing-white-flash-under-tail-21609669.html

https://www.inaturalist.org/observations/194582416

https://www.inaturalist.org/observations/193973921

https://www.inaturalist.org/observations/106546121

https://www.inaturalist.org/observations/80361071

https://www.inaturalist.org/observations/48649354

https://www.inaturalist.org/observations/41828696

https://www.inaturalist.org/observations/10593946

https://www.inaturalist.org/observations/203262951

https://www.inaturalist.org/observations/153367326

https://www.alamy.com/rear-view-of-a-muntjac-deer-with-its-tail-up-in-the-forest-of-dean-image416053307.html

displayed by infants and juveniles during suckling

https://www.inaturalist.org/observations/46359553

Muntiacus vaginalis:

https://www.inaturalist.org/observations/110068081

https://www.dreamstime.com/stock-photo-muntjac-national-park-photo-taken-resting-tree-image89607003

https://www.dreamstime.com/stock-photo-muntjac-national-park-photo-taken-resting-tree-image89606944

https://www.dreamstime.com/stock-photo-muntjac-national-park-photo-taken-resting-tree-image89606982

@matthewinabinett @jeremygilmore @tonyrebelo @variani18 @christiaan_viljoen @paradoxornithidae @beartracker @chewitt1 @gareth_bain @kfinn

Please also see the following

• https://www.inaturalist.org/journal/milewski/85161-variation-in-walking-gaits-in-ungulates-why-some-hoofed-mammals-cross-walk-whereas-others-amble-part-1#
• 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#
• https://www.youtube.com/watch?v=nh9e1xoUJ4Q

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

• the 'normal' or 'default' walking gaits in unguligrade mammals are intermediate between 'diagonal-sequence' and 'lateral-sequence' gaits, and
• there has been no apt term for this in the literature - the detailed work of Innis Dagg (https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2907.1973.tb00179.x and https://originalwisdom.com/wp-content/uploads/bsk-pdf-manager/2019/03/Dagg_1973_Gaits-in-mammals.pdf and https://uwspace.uwaterloo.ca/handle/10012/14529) and Hildebrand (https://www.originalwisdom.com/wp-content/uploads/bsk-pdf-manager/2019/04/Hildebrand_1977_Analysis-of-Asymmetrical-Gaits.pdf and https://academic.oup.com/jmammal/article-abstract/58/2/131/892924?login=false) notwithstanding.

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

• Mazama https://www.inaturalist.org/observations/184029864 and https://www.inaturalist.org/observations/148448279 with
• Papio https://www.inaturalist.org/observations/197758249 and Nasalis https://www.naturepl.com/stock-photo-proboscis-monkey-nasalis-larvatus-male-walking-on-the-mudflats-of-a-image01352001.html

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,

• the hind foot is placed after the opposite fore foot is placed (https://www.inaturalist.org/observations/148448278); by contrast, in the monkeys, the hind foot is placed before the opposite fore foot is placed (https://www.youtube.com/watch?v=EZhO2dhlIFI and https://www.sciencephoto.com/media/1223177/view/chacma-baboon-walking);
• the hind foot superimposes on the print of the fore foot on the same side; by contrast, in the monkeys the hind foot lands to the side of the fore foot (https://depositphotos.com/photo/male-hamadryas-baboon-77413598.html);
• cross-walking tends to occur only in furtive/halting locomotion; by contrast, in the monkeys, cross-walking terrestrially tends to occur with a bold demeanour;
• the feet tend to be lifted high off the ground, as if to avoid making rustling sounds against low plants; by contrast, in the monkeys, the feet swing low;
• some spp. may tend to bob the head back and forth in synchrony with their limb-movements; by contrast, all the monkeys hold the head steady; and
• the figure intermittently 'freezes' vigilantly/suspiciously with one or two feet suspended off the ground (https://www.inaturalist.org/observations/145704914 and https://www.inaturalist.org/observations/143222891 and https://www.inaturalist.org/observations/173412545 ); by contrast, in the monkeys, there is no sudden cessation of movement in an attempt to blend into the environment in concealment from predators.

Part of the reason why ruminants and monkeys deviate, in opposite directions, from the synchronous placement of the diagonally-opposite feet may be

• their different body-proportions, and
• the fact that the former are unguligrade, whereas the latter are plantigrade (hind) and facultatively digitigrade (fore, https://mammals-locomotion.com/walking.html).

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

• there is an 'ape-like' conformation, with relatively long fore legs that facilitate climbing, and
• the hind feet are plantigrade (https://en.wikipedia.org/wiki/Plantigrade).

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,

• the proportionately long hind leg of the ruminants takes a long time to swing fully from lifting to placement, thus landing well after the diagonally-opposite fore leg, whereas
• the proportionately short hind leg of the monkeys takes a short time to perform the analogous swing.

Finally, two relevant differences between the ruminants and the monkeys are that

• in adults of the latter, cross-walking is categorically the only terrestrial walking gait; by contrast, most/all of the ruminants that cross-walk are capable of grading into a semi cross-walk when walking rapidly; and
• when speeding up from walking to running, the former trot, whereas the latter immediately canter/gallop; indeed, no primate is known to trot.

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

https://www.inaturalist.org/observations/200929949

https://www.inaturalist.org/observations/196352729

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

• conspicuously dark pelage on the brisket (https://www.merriam-webster.com/dictionary/brisket),
• conspicuously dark pelage on the ventral surface of the thorax (https://www.inaturalist.org/observations/45881470),
• conspicuously pale pelage on the entire inner surface of the upper foreleg (including the axilla, https://www.merriam-webster.com/dictionary/axilla), and
• conspicuously pale pelage on the inner and posterior surface of the lower foreleg.

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

https://www.inaturalist.org/journal/milewski/92119-impalas-aepyceros-and-giraffes-giraffa-share-the-same-walking-gait-namely-an-amble#

https://www.inaturalist.org/journal/milewski/92356-illustrations-of-the-walking-and-stotting-gaits-of-the-pronghorn-antilocapra-americana#

https://www.inaturalist.org/journal/milewski/91695-why-cross-walking-gaits-seem-unrecognisably-different-in-ruminants-and-like-size-terrestrial-monkeys#

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#

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#

https://www.inaturalist.org/journal/milewski/91587-walking-gaits-in-cervidae-deer-tend-to-cross-walk-as-opposed-to-the-ambling-typical-of-many-bovids-part-3-discussion#

@beartracker @magcl @ptexis

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,

• to pick their way quietly through the undergrowth, then 'freeze' on two legs upon hearing an ominous rustling, and
• to wade through water and snow, and to step over fallen logs, in the case of the species of deer with the longest legs, namely the moose (Alces alces, https://www.shutterstock.com/da/video/clip-1110160859-bull-moose-walks-off-road-into-wilderness and https://www.youtube.com/watch?v=zUE5FK3l_Lo and https://www.youtube.com/watch?v=MV3yLbKke-c).

It is only in two categories of ruminants that all 'diagonality' seems to have been abandoned while walking.

These are

• giraffes, which achieve stability by means of the cantilever-effect of the long and massive neck, and
• 'plains game', adapted to open environments where hiding is impractical, and compensating for this in various ways in their anti-predator strategies.

'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

• humped withers,
• migration/nomadism, and
• extreme speed and endurance when galloping and cantering.

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

• dependence on woody plants,
• sedentariness (excluding nomadism, let alone migration),
• intimate gregariousness, and
• extreme bounding while fleeing.

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

• absent in giraffes,
• used by wildebeests and hartebeests only for display, and
• peculiarly absent in impalas.

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

• body size and shape (https://pixabay.com/photos/giraffes-impala-safari-animals-5916620/ and https://www.shutterstock.com/da/image-photo/giraffe-impala-kruger-national-park-south-79715629 and https://www.alamy.com/giraffe-and-black-faced-impala-at-a-waterhole-image225907584.html and https://www.alamy.com/giraffe-couple-and-impala-in-kruger-national-park-south-africa-specie-giraffa-camelopardalis-family-of-giraffidae-image242053468.html and https://www.mediastorehouse.com.au/fine-art-storehouse/giraffe-giraffa-camelopardis-blacked-faced-12529903.html), and
• ways of fleeing from predators.

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

• https://www.inaturalist.org/journal/milewski/85161-variation-in-walking-gaits-in-ungulates-part-1-why-some-hoofed-mammals-cross-walk-whereas-others-amble#, and
• https://www.inaturalist.org/journal/milewski/79019-field-notes-from-an-excursion-with-the-dromedary-camelus-dromedarius-northern-kenya-1990-1991#

@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.

• various walking gaits, and
• various display gaits, the function of which is partly to signal individual fitness to predators and/or conspecifics.

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://stock.adobe.com/video/pronghorn-antelope-walking-in-the-plains/191515413?as_campaign=ftmigration2&as_channel=dpcft&as_campclass=brand&as_source=ft_web&as_camptype=acquisition&as_audience=users&as_content=closure_asset-detail-page

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://www.shutterstock.com/da/video/clip-1093543127-pronghorn-antelope-walking-through-utah-desert-during

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:

https://www.youtube.com/watch?app=desktop&v=EMncnjX7vcU

https://pngtree.com/freebackground/pronghorned-antelope-running-through-field-hunting-color-fauna-photo_3819221.html

Scroll in https://content.govdelivery.com/accounts/USDOI/bulletins/3478106

Scroll in https://www.azcentral.com/picture-gallery/news/local/glendale/2015/09/24/11-things-you-might-not-know-about-luke-air-force-base/72030292/

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

https://www.alamy.com/stock-photo-pronghorn-antelope-antilocapra-americana-fawn-running-in-grassland-26797480.html

DISCUSSION

The pronghorn conforms to a category of ungulates that I have called 'plains game'.

This is because it combines the following features/traits:

• exposed habitat, lacking cover,
• gregariousness,
• cursoriality and migration (https://www.youtube.com/watch?app=desktop&v=ig2VR6aAu4M),
• lateral placement of the eyes (https://www.inaturalist.org/observations/86028387 and https://www.inaturalist.org/observations/20720325 and https://www.youtube.com/watch?v=j5QQ85aXipc and https://www.inaturalist.org/observations/123766827 and https://www.inaturalist.org/observations/79483159),
• conspicuous colouration, even at distance (https://www.inaturalist.org/observations/67782104 and https://www.inaturalist.org/observations/70291649 and https://www.inaturalist.org/observations/116295944 and https://www.inaturalist.org/observations/9807652 and https://www.inaturalist.org/observations/197435261 and https://www.inaturalist.org/observations/33663443 and https://www.inaturalist.org/observations/2678702 and https://www.inaturalist.org/observations/53522820),
• minor sexual dimorphism (https://www.inaturalist.org/observations/144092409 and https://www.inaturalist.org/observations/128676306 and https://www.inaturalist.org/observations/187659485 and https://www.inaturalist.org/observations/138672584 and https://www.inaturalist.org/observations/146685807),
• reluctance to jump over fences (https://tpwd.texas.gov/publications/pwdpubs/media/pwd_lf_w7000_1787.pdf and https://www.facebook.com/watch/?v=854823252123488 and https://www.greatfallstribune.com/videos/news/2017/05/05/watch-pronghorn-crawling-underneath-fences/101298706/ and https://www.youtube.com/watch?v=hnVHZBin5x4 and https://www.youtube.com/watch?v=XyvfiNDtiAI and https://www.inaturalist.org/observations/115502513 and https://www.youtube.com/watch?v=VyVwSi4A6ps and https://www.youtube.com/watch?v=aJMTc8wqDl0), and
• seasonal reproduction.

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

• most resembling 'plains game', e.g. Cervus canadensis, and
• with the most lateral placement of the eyes, e.g. Dama dama.

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.

• the hind foot lifts only once the contralateral fore foot lands (= what I term 'nearly ambling'), and/or
• the hind foot lands slightly anterior to the track of the ipsilateral fore foot (possibly shown in https://www.inaturalist.org/observations/775048).

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

• exaggerated cross-walking (resembling that in cervids e.g. Odocoileus, https://www.sierraclub.org/sierra/assisted-migration-helps-animals-adapt-climate-change), and
• exaggerated trotting (= proud-trotting, resembling that in bovids e.g. Alcelaphus).

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.

Stotting in the pronghorn less bouncy than in the sympatric Odocoileus hemionus hemionus. The footfall-pattern is similar, but the height is so much less that stotting hardly seems to demonstrate fitness in the pronghorn.

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 white piloerection of a 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,

• under which circumstances does ambling occur?
• why - in adaptive terms - has the pronghorn retained a cross-walking gait, despite otherwise conforming to 'plains game'? and
• why does stotting occur mainly for intraspecific display and in adults, rather than - as in most other ruminants - mainly for anti-predator display and in infants and juveniles?

Also see

• https://www.inaturalist.org/journal/milewski/52136-the-mane-as-a-little-known-aspect-of-the-erectile-bleeze-of-the-pronghorn-antilocapra-americana#
• https://www.inaturalist.org/posts/52201-the-peculiar-showiness-of-the-subauricular-gland-of-the-pronghorn-antilocapra-americana#
• https://www.inaturalist.org/posts/52221-why-the-pronghorn-antilocapra-americana-has-a-striped-neck#
• https://www.inaturalist.org/journal/milewski/52296-interpreting-the-buccal-semet-of-the-pronghorn-antilocapra-americana#

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

• to be accentuated by dark, short pelage in females and juveniles, but
• to lack this accentuation in adult males - in which the dark horns draw attention undistracted by the ear pinnae.

The sexual dimorphism of the head adornments in the pronghorn is limited, because

• the horns in males are smaller than in cervids of similar body mass, and
• females, too, possess horns, albeit small and individually variable ones.

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 (https://www.inaturalist.org/observations/208917977).

In cervids sympatric with the pronghorn, the anterior surface of the ear pinnae is conspicuously dark-edged in winter pelage. It is possible that a similar seasonal pattern applies to the pronghorn.

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.alamy.com/close-up-portrait-of-a-pronghorn-antilocapra-americana-looking-at-the-camera-utah-united-states-of-america-image218519416.html

https://www.flickr.com/photos/tomblandford/53083685549

https://www.reddit.com/r/wildlifephotography/comments/19180dc/pronghorn_antelope_near_agate_utah/

https://www.gettyimages.com.au/detail/photo/portrait-of-female-pronghorn-antelope-royalty-free-image/1470317568?phrase=pronghorn+antelope&adppopup=true

https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-pronghorn-usa-north-america-royalty-free-image/2025130414?phrase=pronghorn+antelope&adppopup=true

https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-standing-on-grassy-field-royalty-free-image/964990848?phrase=pronghorn+antelope&adppopup=true

https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-western-montana-royalty-free-image/1833226632?phrase=pronghorn+antelope&adppopup=true

https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-female-close-up-royalty-free-image/1289599649?phrase=pronghorn+antelope&adppopup=true

https://pbase.com/clinton62/image/147356192

https://www.facebook.com/USFWS/photos/a.419357095774/10159745741580775/?type=3

https://www.agefotostock.com/age/en/details-photo/pronghorn-doe-close-up-close-up-on-face-of-pronghorn-doe-chewing-on-grass-custer-state-park-south-dakota/MEV-12906106

https://www.shutterstock.com/da/image-photo/wild-pronghorn-antelope-doe-south-dakota-2421372029

https://www.shutterstock.com/da/image-photo/young-californian-whitetailed-deer-looking-camera-1557667202

https://www.shutterstock.com/da/image-photo/pronghorn-winter-antilocapra-americana-yellowstone-national-1813213273

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.alamy.com/close-up-portrait-of-a-pronghorn-antilocapra-americana-looking-at-the-camera-utah-united-states-of-america-image218519416.html

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.shutterstock.com/da/image-photo/pronghorn-antelope-on-prairie-detailed-close-114676864?consentChanged=true

https://www.masterfile.com/image/en/841-06806323/pronghorn-antilocapra-americana-buck-custer-state

https://psmag.com/environment/fracking-away-the-wildlife-44012

https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-royalty-free-image/172124570?phrase=pronghorn+antelope&adppopup=true

https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-male-close-up-royalty-free-image/1525989497?phrase=pronghorn+antelope&adppopup=true

https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-close-up-shot-royalty-free-image/528094801?phrase=pronghorn+antelope&adppopup=true

https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-male-close-up-royalty-free-image/1289599538?phrase=pronghorn+antelope&adppopup=true

https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-buck-feeding-on-sagebrush-grand-royalty-free-image/723508899?phrase=pronghorn+antelope&adppopup=true

https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-profile-royalty-free-image/528094863?phrase=pronghorn+antelope&adppopup=true

https://www.gettyimages.com.au/detail/photo/male-pronghorn-antelope-antilocapra-americana-royalty-free-image/128144230?phrase=pronghorn+antelope&adppopup=true

https://www.masterfile.com/image/en/841-06446816/pronghorn-antilocapra-americana-buck-yellowstone-national

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.alamy.com/pronghorn-antilocapra-americana-male-portrait-yellowstone-national-park-wyoming-usa-image217620926.html

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/

@variani18 @ludwig_muller

Please see

• https://www.inaturalist.org/posts/57595-the-bambis-part-4-a-new-species-of-klipspringer-in-southern-africa#
• https://www.inaturalist.org/journal/milewski/57660-the-bambis-part-5-possible-new-species-names-for-klipspringers-in-southern-africa#
• https://www.inaturalist.org/posts/57741-correcting-the-misidentification-of-klipspringer-subspecies-tyleri-in-inaturalist#

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/klipspringer-male-kruger-national-park-south-africa-royalty-free-image/685029237

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

https://www.dreamstime.com/stock-photo-klipspringer-closeup-portrait-oreotragus-oreotragus-small-african-antelope-image44207351

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.

• a consistent habit of opening the mouth while galloping,
• long-range visual vigilance,
• long-distance signalling by means of 'semaphoric' pale patches on the pelage, and
• a lack - relative to other forms of 'plains game' - of displays of individual fitness to scanning predators.

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

• extremely large eyeballs, both absolutely for a mammal and relative to body size, and
• bony orbits that protrude from the skull laterally, to a degree possibly exceeding that in any other ungulate.

The long-distance signalling of the pronghorn is indicated partly by a conspicuously pale patch on the hindquarters (https://www.inaturalist.org/observations/211220855 and 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

• extreme piloerection of the acetabulo-ischiopygal bleeze, which expands it into a disc-like feature with accentuated borders (https://www.flickr.com/photos/189038430@N06/53349701594/in/faves-58287925@N05/ and https://www.reddit.com/r/AnimalPorn/comments/b7nc5f/pronghorn_doe_in_alert_posture_oc/#lightbox and https://www.facebook.com/watch/?v=595650625349272 and https://www.agefotostock.com/age/en/details-photo/pronghorn-gabelbock-gabelantilope-antilocapra-americana-in-winter-attentive-animal-scared-erecting-its-white-hairs-on-its-rump-yellowstone-area-usa/VX1-3111450 and https://pngtree.com/freebackground/pronghorn-antelope-buck-running-through-field-digital-fauna-animal-photo_3822003.html), and
• peculiarly luminous whiteness when thus piloerected, appearing like a flashing beacon, even (to the human eye) at distances of more than one kilometer (https://pngtree.com/freebackground/pronghorn-antelope-in-saskatchewan-field-wild-animal-rural-horizontal-photo_3839252.html and https://pngtree.com/freebackground/pronghorn-antelope-male-sprinting-across-saskatchewans-grassy-expanse-photo_3839357.html).

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

• stotting, to the extent that it occurs among adults, is displayed mainly sociosexually, rather than to potential predators,
• 'style-trotting' is rather poorly-developed, and
• neither stotting nor proud-trotting occur in juveniles, even while playing.

This raises the question:

Selenium:

https://www.horizons-mag.ch/2017/04/03/the-world-map-of-a-trace-element/

https://www.researchgate.net/figure/Selenium-distribution-and-availability-in-regions-of-the-continental-United-Sates-Panel_fig3_228832815

https://extension.uga.edu/publications/detail.html?number=B1390&title=selenium-in-georgia-soils-and-forages-importance-in-the-livestock-industry

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://meridian.allenpress.com/jwd/article/32/1/9/121989/TOXICOLOGIC-EVALUATION-OF-A-HIGH-SELENIUM-HAY-DIET

https://customequinenutrition.com/blogs/nutrients/selenium-101

https://www.researchgate.net/figure/Indicators-of-environmental-selenium-status-for-the-USA-Selenium-rich-environments_fig2_40455792

https://bioone.org/journals/journal-of-zoo-and-wildlife-medicine/volume-32/issue-3/1042-7260_2001_032_0373_PCDIHR_2.0.CO_2/PRESUMPTIVE-COPPER-DEFICIENCY-IN-HAND-REARED-CAPTIVE-PRONGHORN-ANTILOCAPRA-AMERICANA/10.1638/1042-7260(2001)032[0373:PCDIHR]2.0.CO;2.short

https://link.springer.com/article/10.1007/s10344-012-0645-z

https://www.pharmanord.com/history-of-selenium-research