Three odd gaits in one brief video

Today I stumbled upon a video clip so packed with biological interest that I would recommend watching it before it vanishes from the Web: https://www.getaway.co.za/environment/aardvark-outwits-brown-hyena/, the location being https://en.wikipedia.org/wiki/Mabula_Game_Reserve.

We see an individual of the aardvark (Orycteropus afer, https://en.wikipedia.org/wiki/Aardvark) foraging in broad daylight, which is already exceptional because this is one of the most strictly nocturnal of large African mammals.

Then enters an individual of the brown hyena (Parahyaena brunnea, https://en.wikipedia.org/wiki/Brown_hyena), an ostensible specialist on scavenging and an exceptional sighting in its own right although this species is not strictly nocturnal.

Bear in mind that the protagonists are about like-size (brown hyena adult averages 40 kg), but with divergent morphological specialisations. The aardvark is the largest specialised eater of termites and ants on Earth, with extremely muscular legs and large claws. The brown hyena has bone-crushing teeth (see https://en.wikipedia.org/wiki/Brown_hyena#/media/File:Hyaena_brunnea_1zz.jpg) and extremely economical hindquarters in which the shortness of the hind feet is compensated by extreme swing of the tarsal joint (https://www.inaturalist.org/observations/33937313). The aardvark is designed to dig extremely rapidly whereas the brown hyena is designed to walk long distances on an empty belly.

Action: the brown hyena chases the aardvark at full sprint, apparently intent on killing it in defiance of any reputation as a mere scavenger. Can the bite of this 'postcarnivore', unaccompanied by any sharp claws, possibly subdue such nuggety prey?

The brown hyena catches up, but the aardvark manages to somersault down a hole, frustrating the would-be killer. Then, a group of the blue wildebeest (Connochaetes taurinus taurinus), an odd-looking species in its own way, chases the brown hyena off the scene, in a surprising show of aggression towards this 'mere scavenger'.

What interested me particularly is that this footage revealed one new gait every minute. These species can all gallop, but they are strangely divergent in the sequence of limb-movements when not sprinting - perhaps because they are so peculiar morphologically that they look like chimeras.

The aardvark seems like a badger-on-ballet-shoes with a conical tail, a tubular snout and hare-like ears. The brown hyena has a strangely sloping back and long neck, nosferatu-ears, and a cross-grained cape-like mane. The blue wildebeest also has a sloping back and a strange mane and tail. And each is odd in its locomotory gearing, although not necessarily rhyming with reason.

The aardvark is perhaps the only fully terrestrial, digitigrade mammal which uses a perfect cross-walk, the legs moving in diagonal pairs (see https://www.kimballstock.com/results.asp?db=a&txtkeys1=aardvark and https://creatures-of-the-world.fandom.com/wiki/Aardvark?file=Aardvark_fs.jpg). This has not been pointed out in the literature but is obvious once one develops a search-image for walking gaits.

The brown hyena has its own odd walk in that the 'hock' seems hypermobile (see https://www.inaturalist.org/observations/68997824 and https://upload.wikimedia.org/wikipedia/commons/b/be/Brown_Hyena_%28Parahyaena_brunnea%29_%286472940707%29.jpg). But what is really unusual is that, instead of trotting like other carnivores, it paces like a camel. (Watch for this after the aardvark vanishes and the brown hyena gives up on digging.) Also see https://www.earthtouchnews.com/natural-world/predator-vs-prey/guess-what-this-brown-hyena-had-for-dinner/.

And, for its part, the blue wildebeest is also more reluctant to trot than most other ungulates, gearing up from a walk straight into a canter (see https://videohive.net/item/wildebeests-walking-and-running/26412070 for a different species of wildebeest).

So here we have an expose of specialised gaits which have yet to be explained in adaptive terms. The aardvark has slowed down the trot to convert the same limb-movements into a walk. The brown hyena has speeded up its walk in replacement of any trotting gear. And the blue wildebeest has just skipped the trot, going from first gear straight to third.

'Go figure'.

Posted on August 02, 2021 11:47 AM by milewski milewski

Comments

Thank you for all the wealth of information in your beautifully written posts!! Delightful :-) And your passion for the animals shines through enchantingly.

Thank you.

Posted by karoopixie almost 3 years ago

@karoopixie Many thanks for your appreciation, it means so much and I trust that our community can enjoy many more of the wonders of nature together.

Posted by milewski almost 3 years ago

I noted the following in Perth Zoo, on 3 May 2003:

SURICATA SURICATTA

I observed Suricata suricatta, walking slowly and interruptedly as the animal investigated its environment.

Its walking gait was more like a cross-walk than those of many mammals. Instead of 'scuffing up', the hind foot is placed just behind the fore foot, before the latter is lifted. This was a plodding, pedestrian gait, not flowing as are the walking movements of so many mammals.

https://www.picfair.com/pics/011534327-walking-meerkat

https://www.alamy.com/suricate-slender-tailed-meerkat-suricata-suricatta-walking-in-the-savannah-side-view-south-africa-kgalagadi-transfrontier-national-park-image255390809.html

https://www.dreamstime.com/meerkat-walking-ground-meerkat-suricate-suricata-walking-ground-outstretched-tail-seen-profile-genus-image251432391

https://www.agefotostock.com/age/en/details-photo/meerkat-suricata-suricatta-adult-running-tswalu-game-reserve-kalahari-north-cape-south-africa-africa/IBK-5054309/1

https://www.agefotostock.com/age/en/details-photo/meerkat-suricata-suricatta-adult-running-tswalu-game-reserve-kalahari-north-cape-south-africa-africa/IBK-5054307/1

Suricata suricatta climbs rather well (https://www.kimballstock.com/preview.asp?db=a&image=AFW+12+KH0032+01) for a species associated with open vegetation and burrowing. Perhaps its walking gait - which is relatively stable and deliberate - is associated with this scansorial ability.

When the animal switched to purposeful walking in a particular direction, it seemed to break into a 'dog-trot', i.e. a diagonal gait just qualifying as a run, not a walk.

DASYURUS GEOFFROYI (https://www.inaturalist.org/taxa/40169-Dasyurus-geoffroii)

This marsupial seemed to walk similarly to S. suricatta.

PONGO

This ape walks like a baboon, but differs in that it places the hind foot slightly in front of the fore foot on the same side.

In order to do this, it has to place the hind foot beside (and slightly in front of) the fore foot.

The left hind foot is placed left of the left fore foot, and the right hind foot is placed left of the right fore foot - or vice versa, unless walking shows 'handedness'.

So, the obvious discord between the fore and hind limbs is solved by the hind foot passing the fore foot, not by the 'scuffing up' seen in various mammals.

I have yet to find any photos or videos that show the walking gait of Pongo clearly.

https://es.123rf.com/photo_142329757_adult-orangutan-walking-on-the-ground-in-the-wildlife-conservation-center.html

https://www.snexplores.org/article/orangutans-take-low-road

Posted by milewski about 1 year ago

@botswanabugs @paradoxornithidae @karoopixie

CAN ELEPHANTS RUN?

My reference is Hutchinson J R Famini D, Lair R, and Kram R (2003) Are fast-moving elephants really running? Nature 422 (6931): 493-494.

https://www.nature.com/articles/422493a

https://www.newscientist.com/article/dn3583-elephants-need-for-speed-defies-definition/

These authors measured speeds up to 25 km/h in Elephas maximus (https://www.inaturalist.org/taxa/43697-Elephas-maximus).

(The average sprinting speed for human athletes, over short distances, is 29 km/h (https://marathonhandbook.com/average-human-sprint-speed/). However, most human individuals (probably <20 km/h) would be rapidly outdistanced, under field conditions, by the average individual of E. maximus.)

"Our elephants maintained the same walking footfall pattern...and always kept at least one foot in contact with the ground."

However, the duty factor is the fraction of a complete sequence of footfalls for which a given foot is in contact with the ground.

Usually, running is defined as having duty factor <0.5. Their experimental animals were found to have duty factor as little as 0.37.

"The elephants routinely exceeded Fr 1.0 (https://en.wikipedia.org/wiki/Froude_number), reaching Fr values as high 3.4 - speeds that are inconsistent with a quadrupedal walking gait".

The argument may be too technical for many naturalists, and I suspect that the 42 individuals studied were mainly juveniles.

However, this study may help to explain how elephants can outrun humans, despite being technically unable to run. These proboscideans make the most of the fact that their legs are absolutely longer than those of humans (https://www.youtube.com/watch?v=6_4HTPgGSuw), using as rapid as possible a version of their walking gait.

Posted by milewski about 1 year ago

TRICHOSURUS VULPECULA (https://www.inaturalist.org/taxa/42808-Trichosurus-vulpecula)

In January 2002, I observed footage of Trichosurus vulpecula on Barrow Island, Western Australia (https://www.imdb.com/title/tt0903440/).

This marsupial is an approximate ecological counterpart for the primate Otolemur crassicaudatus (https://www.inaturalist.org/taxa/43567-Otolemur-crassicaudatus) in southern Africa, albeit with a smaller brain and quite different reproduction.

So, I was intrigued to see that, when walking fairly slowly on the ground, T. vulpecula does not share the diagonal gait of the primate.

Instead, it uses the normal mammalian gait of moving one foot at a time (https://www.shutterstock.com/video/clip-16301536-possum-walking-wandering-city-night-sydney-australia and https://www.youtube.com/watch?v=-ragkqclJaE and https://www.youtube.com/watch?v=04SRsOnqfNs), much like wombats (Vombatidae, https://www.inaturalist.org/observations?place_id=any&taxon_id=43001&view=species) and Tachyglossus (https://www.inaturalist.org/taxa/43239-Tachyglossus-aculeatus).

This slow gait is hard to illustrate, but can possibly be seen in https://www.inaturalist.org/observations/148595730 and https://www.inaturalist.org/observations/95931242 and https://www.inaturalist.org/observations/148594933.

However, what was apparent was that T. vulpecula on the ground readily breaks into what looked like a slow trot, slightly faster than a walk, hardly lifting its feet above the ground. This is its slightly hasty 'walk'.

This gait is clearly illustrated in https://www.inaturalist.org/observations/15969919 and https://www.inaturalist.org/observations/142497978 and https://www.inaturalist.org/observations/141580695 and https://www.inaturalist.org/observations/89760978 and https://www.inaturalist.org/observations/32861038 and https://www.inaturalist.org/observations/18927510.

What this means is that T. vulpecula resembles the domestic dog (Canis familiaris) in its slow gaits. However, if in the diagonal gait it never actually has all four feet off the ground (even for a split-second), T. vulpecula does, after all, 'cross-walk' like its primate counterpart.

Posted by milewski about 1 year ago

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