Animal Locomotion: Understanding Quadruped Gaits and Their Evolution, Slides of Computer Graphics and Animation

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Animal Gaits

Ancestral Tetrapods

 All land based vertebrates evolved from an original ‘tetrapod’ ancestor  The tetrapod was like a primitive reptile- closer to a fish  The 4 legs were adaptations of swimming fins and the creature moved on land by a combination of ‘paddling’ with its legs and ‘swimming’ with it’s spine  All present day quadruped vertebrates are based on the same underlying construction, but with various adaptations  Even snakes, birds, dolphins, and whales evolved from the ancestral tetrapod and still show many similarities

Quadrupeds

Stances

 Some animals, such as humans and bears walk flat footed (palmate)  Some, like horses and cattle walk more on their fingers (digitate)  Smaller or stockier animals sometimes walk with wide stances (sprawling gaits) (these include insects, many reptiles, and some small mammals)  Larger animals tend to walk with straighter legs

Quadruped Walk

Walk

 The basic slow gait of most quadrupeds is the walk  Very slow walks may involve 3-4 legs on the ground, but normal walks involve 3 legs on the ground with a brief moment with only 2  The duty factor is therefore relatively high (.6 ~ .8)  Actual timing of walk gaits may vary from the diagram

Walks

Trot

Trot

 The trot is a medium paced gait where alternate diagonal legs step nearly in sync (though often slightly led by the forefoot)  The duty factor is usually relatively low (<.4) and there are moments where all 4 legs are off the ground (actually, cats sometimes trot at a higher duty factor…)  Before Muybridge, most horse trainers believed a trotting horse always had at least one foot on the ground

Pace / Rack

Pace / Rack

 The rack or pace has similar

qualities to the trot, but

horses are rarely trained to

perform this gait

 This gait is considered to be

the least comfortable for a

rider, but supposedly offers

better traction than the trot

 Most camels use this as

their primary gait

Transverse Gallop

Transverse Gallop

 The gallop is the fastest quadruped gait  The gallop involves an alternation between the front and back pairs of legs, but slightly out of sync  There are several subtle variations on gallops, but they are generally separated into transverse and rotary gallops  Horses tend to prefer the transverse gallop, as do most other quadrupeds

Rotary Gallop

Rotary Gallop

 Rotary gallops involve a

circular LR-RL timing (as

opposed to the zig-zagging

LR-LR timing of the

transverse gallop)

 Many dogs use a rotary

gallop at high speeds, as do

a few other quadrupeds

Feline Gallop

Feline Gallop

 For feline (cat-type) gallops, the timing is like: front-back-pause  After the back legs push off, all four legs are in the air  This sometimes known as a leaping gait

Bound

Bound

 Some quadrupeds gallop in

such a way that the front

and back pairs of legs are in

sync

 This is known as a bounding

gait

Hexapod Gaits

Off-sync back to

front wave gait

Tripod gait

Octapod Gaits

 Spiders are octapods (8 legs)

 They tend to have very similar gaits to

hexapods

 Off-sync back to front wave gait for slow

movement

 Quadrapod gait (not quadruped)