Variation in walking gaits in ungulates, part 1: why some hoofed mammals cross-walk, whereas others amble

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Ungulates are defined by their feet, which bear hooves. Given this pedal specialisation, one might expect all ungulates to walk with similar gaits.

But this is not the case.

In this Post, I classify, illustrate, and explain the walking gaits of ungulates, which vary considerably and in ways related to habitats and niches.

Let us begin by referring to one of the most relatable of non-ungulate mammals, similar in body size to fairly small ungulates, and sharing some of their habitats, viz. baboons (genus Papio).

Baboons provide a useful starting point because they are anthropoid primates, walking with a simple gait that the human observer can easily understand.

Baboons cross-walk, moving the legs approximately in diagonal pairs ( and and and

Humans walk with a similar diagonal pattern of swinging the limbs, except that our bipedality means that our hands remain off the ground (

The gait of baboons, viz. the cross-walk, is a stable gait, because it spreads the weight over left and right sides.

The main disadvantage of the cross-walk is that the hind foot risks colliding with the corresponding fore foot, unless placed to its side. This means a slight sideways swing in the gait, detracting from forward propulsion.

In summary so far, the cross-walk is stable but somewhat inefficient. It is not a particularly smooth gait for any fairly long-legged mammal.


Now, returning from primates to ungulates:

Hippopotamidae are technically hoofed mammals, despite the fact that their feet are only slightly unguligrade.

Hippopotamus cross-walks ( and and and

Furthermore, this is a more 'perfect' cross-walk than in baboons, in which the fore foot swings forward noticeably before the opposite hind foot does.

In Hippopotamus, there is no risk of interference between hind and fore feet, because the legs are short relative to the long body.

The pygmy hippo (Hexaprotodon) walks surprisingly differently from its large relative. The synchrony between fore and diagonally opposite hind is lost, so that the stride pattern resembles 'one foot at a time' (t and and and scroll in

The difference within Hippopotamidae, between species differing ten-fold in body mass, seems to confirm that, in ungulates, the cross-walk is associated with a premium on maintaining stability.

For the rest of this Post, I will refer to the gait exemplified by the pygmy hippo as a 'semi cross-walk'.


From the least unguligrade of ungulates, let us now turn to some of the most unguligrade, viz. Giraffa.

Part of the reason for the evolution of hooves is increased locomotory efficiency and speed, at some expense of stability.

This is taken to extremes in Giraffa, in which

  • the length of the legs means increased efficiency in walking, without particular regard to stability,
  • the spread of weight between left and right is compromised, and
  • balance is maintained partly by means of the cantilevering effect of the long, massive neck.

The result is an ambling gait, in which the legs are swung not in diagonal pairs but instead in like-sided pairs ( and and and

To summarise so far:

Ungulates are like 'tetrapods on stilts', to varying degrees. No ungulate with legs proportionately longer than those of Hippopotamus uses a full cross-walk. This is presumably because such a gait would trade off necessary efficiency for superfluous stability, diminishing the advantage of being unguligrade in the first place.

Those ungulates - beyond Hippopotamidae - emphasising stability tend, presumably, to be associated with

Those ungulates emphasising locomotory efficiency tend instead to be associated with

  • firm, smooth ground,
  • open vegetation, and
  • cursoriality, with a tactic of fleeing from predators with speed and endurance.

The cross-walk, semi cross-walk, and amble constitute a continuum, in which the walking gaits represent gradations rather than a dichotomy. In the intermediate zone, where is the dividing line between the categories of semi cross-walk and amble?

Please bear in mind that the term 'amble' has been used ambiguously in the case of the horse (Equus caballus), which has been selectively bred for extreme versatility in its running gaits (

There are two ways to distinguish the semi cross-walk from the amble, as follows:

  • a criterion based on avoidance of collision of hind with fore hoof, and
  • a criterion based on lifting of hind hoof relative to landing of opposite fore hoof


When the hind hoof swings forward, the fore hoof on the same side lifts either

This subtle distinction is significant, for the following reason. The former means the placement of the hind hoof behind the track of the fore hoof, thus limiting the length of the stride and, correspondingly, the efficiency of locomotion, whereas the latter allows the hind hoof to be placed in or in front of the track of the fore hoof - thus not limiting the length of the stride as the animal goes from slow walking to rapid walking.

Semi cross-walk:











To illustrate this distinction even more clearly:

Please carefully follow the feet in these footages of walking in Camelus, which usually ambles:

...and, in turn, please note the configuration in the following of specialists in rocky terrain, which are the converse of Camelus in that they cross-walk. I refer to klipspringers (Oreotragus):





Semi cross-walk:

The following show the semi cross-walk of Alces. Please note that, by the time that the fore is about to be placed, the hind has already been lifted, for long enough that the lower leg has swung to the vertical.





The following, correspondingly, show the semi cross-walk of the largest-bodied of all antelopes.





The following, of Alcelaphus, shows the difference between the semi cross-walk of tragelaphins (including Taurotragus) and the amble of alcelaphins (including Alcelaphus). The hind hoof is lifted only once the fore hoof has touched the ground.


The following shows that Camelus, although similar to Alces in the proportional length of the legs, is similar in walking gait to alcelaphins, and different from Alces.


The horse has been both boon and bane, in the appreciation by naturalists of how ungulates walk.

Boon, because its gaits have been thoroughly studied and illustrated.

Bane, because

  • in the horse the term 'amble' has been transferred to specialised running gaits (e.g. the tolt), while
  • in both the horse and wild equids (e.g. see Estes, page 237), the normal walking gait has slipped to being nameless.

The reason for this namelessness is that the normal walking gait of the horse and other equids ( is exactly intermediate between a semi cross-walk and an amble.

(This applies also to e.g. the African savanna buffalo, see comment below.)

In the case of Hippopotamus and Giraffa, the walking gaits are - unlike the case of equids - obvious. The former cross-walks, while the latter ambles, despite both of these ungulates being megaherbivores.

This difference is unsurprising, given that

  • in Giraffa, a cross-walk would produce excessive interference between fore and hind feet, and
  • in Hippopotamus, the body would rapidly tip to the side if both legs on that side were simultaneously lifted.

However, the relative weakness of the legs in Hippopotamus also plays a part. Rhinoceroses resemble Hippopotamus in that the hind foot does not reach where the fore foot left off (, yet these megaherbivores walk similarly to equids. This is presumably because the muscularity of the legs aids in maintaining balance.

Given that both Giraffa and (usually) Camelus amble, it is easy to assume that all relatively long-legged ungulates amble.

However, this is not so. Alces has legs proportionately longer than in any other cervid, yet it cross-walks, much like the pygmy hippopotamus.

The adaptive explanation is that Alces relies on locomoting rapidly and efficiently over fallen logs and through deep snow.

As Valerius Geist has pointed out, "when fleeing from enemies they can clear obstacles about...1 m...high without jumping, thanks to their large body and long legs. A wolf or bear on the trail of a moose, however, has to jump to get over such an obstacle...Smaller predators following the moose therefore become fatigued much sooner than the moose. On uneven ground a running moose can pass a horse easily".

The above quote refers to the trotting gait of Alces, which is basically a speeded-up version of the cross-walk, in which all four feet are simultaneously off the ground for part of the cycle. However, the efficiency applies also to cross-walking - with feet lifted high - through cluttered terrain, while Alces forages and commutes.

Another instructive comparison is between the pygmy hippo and klipspringers, which are so extremely specialised for locomotion on rocks that they walk not only on their hooves but on the tips of their hooves ( and

Despite the pygmy hippo being hardly unguligrade and klipspringers being 'hyperunguligrade', both semi cross-walk.

This is presumably because - for different reasons - both emphasise stability over efficiency of locomotion. Klipspringers risk stumbling and injuring themselves on the rocks, while the pygmy hippo risks slipping on mud and tripping on ground-level clutter in rainforest.

(The following needs checking:
A basic difference between baboons ( and ungulates is:
when the former walk, two feet are off the ground at the same time; when the latter walk, there is only one foot off the ground at any moment, for most of the stride-cycle. The instability inherent in having two feet off the ground at the same time is compensated for, in the case of cross-walkers such as baboons, by the decidedly diagonal pattern involved.)

to be continued in

הועלה ב-ספטמבר 30, 2023 03:21 לפנה"צ על ידי milewski milewski


The aardvark (Orycteropus afer) cross-walks, similarly to baboons:

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Aces alces gigas is said to reach a height of 2.1 m at the withers, corresponding to a body mass of about 800 kg. One way to visualise this size is by comparison with the horse (Equus caballus)

On average, the thoroughbred racehorse has a height at the withers that is about 15 cm lower than the average height of adult male Homo sapiens:

The largest individuals of E. caballus have reached the same height, at the withers, as the largest individuals of A. alces:,%2C%20just%20above%20the%20shoulder.)

However, the body mass of the largest-bodied individual (1524 kg) of E. caballus was about double that reached by A. a. gigas. This is largely because the horse ( exceeds the moose ( in the girth of the torso and hindquarters.

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Phacochoerus ambles:

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In the African savanna buffalo (Syncerus caffer), the walking gait seems to be on the borderline between an amble and a semi cross-walk.

On one hand, the fore hoof lifts before the hind hoof on the same side lands - which indicates an amble.

On the other hand, the hind hoof lifts before the fore foot on the opposite side lands - which indicates a semi cross-walk.

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@matthewinabinett @beartracker

Estes (1991), on pages 112-113, states the following about the grey rhebok (Pelea capreolus), under the heading 'postures and locomotion':

"The rhebok has an ambling walk on level ground, which changes to a cross-walk on slopes and broken ground."

The following shows a semi cross-walk, confirming Estes:

However, the following indicate that the semi cross-walk, rather than an amble, is maintained even on level ground:

The following seems to show a remarkably full cross-walk in the grey rhebok, as it walks downslope:

These observations indicate adaptive convergence in walking gaits between Pelea and Oreotragus, which overlap in habitat. I have yet to find any photograph confirming that the grey rhebok ambles, even on level ground.

The trot, a gait not mentioned by Estes for the grey rhebok, is revealed in and This is a running version of the cross-walk. The grey rhebok thus differs from Oreotragus, which does not trot.

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