Bipedal versatility in ruminants, part 1

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Ruminants (deer, bovids, musk deer, giraffes, pronghorns and chevrotains) stand and run on all fours. However, some species are able to free-stand bipedally to forage or to quarrel, and it is here that intriguing patterns await discovery by naturalists.

I refer to standing upright with the back vertical but without propping the forelegs on branches or other supports.

What is obvious from perusal of photos on the Web is that ruminants differ categorically in their bipedal versatility. I have seen thousands of photos of, for example, the impala (Aepyceros melampus), without finding any evidence of free-standing bipedally. By contrast it takes only a few minutes to find such evidence in the case of deer (Cervidae) resembling the impala in body size and proportions.

In this, part 1, I show that many species of deer are bipedally versatile. In part 2, we will see that other families of ruminants lack this versatility except for a few genera of bovids. In part 3, I will offer some explanations of these findings.

The following show that a dozen or more species of deer in at least eight genera, including both sexes, are able to free-stand bipedally. The photographic evidence is clear for both foraging and social antagonism. Free-standing bipedally while quarreling is seen not only in females but also in males while the growing antlers (still in velvet) risk permanent damage from any attempts to butt each other.

In quarreling while free-standing bipedally, a typical action for deer is to flail the fore hooves downwards threateningly. The mouth is held horizontal and the ears are turned back. This suggests that the muzzle-ring functions as a buccal semet in this context; and in the relatively few species possessing suitable patterns on the ears there is also evidence of auricular semets.

Alces alces

This species sometimes forages by standing upright (, but I do not know whether this includes free-standing bipedally

Rangifer tarandus

I suspect that this species forages for lichens in trees during winter by free-standing bipedally, but I have yet to find photos

Odocoileus virginianus

Odocoileus hemionus

Dama dama

Cervus canadensis

Cervus elaphus

Cervus nippon

Rusa unicolor

Elaphurus davidianus

Axis axis

Muntiacus reevesi

to be continued...

Posted on September 03, 2021 09:46 AM by milewski milewski


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