How walking gait and plantigrady differ between the most terrestrial monkey (Erythrocebus) and other semi-terrestrial monkeys (Papio and Nasalis)

https://www.dreamstime.com/beautiful-baboon-park-there-walking-fear-image129501491

https://www.dreamstime.com/beautiful-baboon-park-there-walking-fear-image129501374

https://www.mtsobek.com/travel-journal/adventure-experts/a-rare-look-at-the-ethiopian-gelada-monkey/

@botswanabugs @beartracker @matthewinabinett @paradoxornithidae @jeremygilmore @tonyrebelo @jwidness

OBSERVATION OF (BRIEF, TRANSITORY) TROTTING IN PAPIO

In April 2003, I discovered a new gait while watching a documentary in the series https://www.amazon.com.au/Vets-Wild-Hb-Trude-Mostue/dp/0752217739) about the monkeys at Diani Beach, Kenya (https://en.wikipedia.org/wiki/Diani_Beach).

This gait was exhibited by an adult female individual of Papio cynocephalus (https://www.inaturalist.org/taxa/67683-Papio-cynocephalus).

The location is indicated by the following observations in iNaturalist (https://www.inaturalist.org/observations/30893826 and https://www.inaturalist.org/observations/14355101). The following (https://www.youtube.com/watch?v=raGkyVQ1kkM) helps to set the scene.

The individual in question was carrying a juvenile at the advanced, brown stage (https://www.inaturalist.org/observations/154785531 and https://www.inaturalist.org/observations/101393711), on the ventral surface of the mother's torso.

We see this mother hurrying across a road without resorting to the canter that is the normal relatively slow, running gait in Papio. It retains the diagonal limb-movements of the normal 'cross-walk' of baboons.

However, what was new to me was that it moved rapidly enough that all four feet seemed, for a split-second at a time, to be off the ground - bringing the gait just within the trotting gait that is so typical of the domestic dog (Canis familiaris) when taken for a brisk walk (scroll to first photo in https://www.whole-dog-journal.com/health/your-dogs-physical-characteristics-and-why-they-matter/).

The following (https://cz.123rf.com/photo_45516946_baby-yellow-baboon-papio-cynocephalus-riding-on-its-mothers-back.html) hints that mothers resort to the same nominal trot when the juvenile is riding dorsally.

My interpretation:
This is an easily overlooked gait in Papio, because it occurs only a) in adult females, b) when the juvenile is heavy enough, when riding, to interfere with the normal cantering gait, and c) where the urgency is limited and transitory.

I expect that, were this mother to locomote hastily enough to run unambivalently, it would break into a canter - with the juvenile disembarking and galloping for itself, to keep up.

In summary, what this glimpse, in a documentary, inadvertently showed is that baboons sometimes emulate the gait so familiar in dogs, viz. a trot so slow that it is functionally just a brisk walk. The following (https://www.shutterstock.com/image-photo/beagle-dog-running-trot-700120750) shows unusually clearly that, in this gait, all four feet are off the ground simultaneously for an instant. And the circumstances in which this occurs, in baboons, is when mothers are carrying a relatively heavy juvenile, and accelerate only slightly and briefly.

This observation is novel, because - as far as I know - trotting has not previously been recorded in any anthropoid primate.

The mean body mass of adult females of Nasalis larvatus in Borneo is 12 kg.