Animal Gaits For Animators
My goal with this article is to put in one place a reference guide on quadrupeds’ gaits and their variations. I encourage you to read the whole piece at least once and to come back to a gait’s section when you need it. You’ll find an analysis of footfalls of the most common quadrupeds’ gaits, including which animals each gait suits best. Here, I analyze all six gaits in the order of the speed they provide the animal: walk, amble, trot, pace, canter, and gallop. Each gait has its unique characteristics, from the frequency of steps to the footfall patterns to the number of limbs off the ground at any given time (with increasing air time as speed increases). Each gait shares traits with the previous and following gait so the transition between gaits is smoother. For example, the amble can be seen as the average between the traits of a walk and a trot.
But before we dig into the details of how it works and why we need it, I need to quickly address the obvious why: Why do we move?
Animal locomotion, especially fast movement, can be extremely energy-consuming, so it wouldn’t have evolved if it weren’t indispensable. As with most things in the animal kingdom, it usually comes down to three main motivations: find food, avoid becoming food, and reproduce. Where we find our food source, how fast our lunch is moving, and how we protect ourselves from danger can drastically influence the way we move. Think of the difference between a monkey, a horse, and a turtle. Ultimately, if something we need isn’t exactly where we are, we need to go where it is. But if this was our only concern, we wouldn’t worry so much about how fast we get there. Speed, for the most part, becomes vital only when predators enter the picture, at least a speed relative to the predator’s. Animals who find safety inside their shells like turtles don’t need to move fast and can save a lot of energy that way. If your safety comes from outrunning whatever is chasing you, being faster means living another day. If you are the predator on the chase, outrunning your prey means feeding yourself another day, so both sides had evolutionary motives to achieve faster speeds.
Discovery Of The Bipod Gait [with Video]
Not all creatures move the same way; some gaits are better adapted to keeping up over longer distance, others for explosive movement and sprinting.
Clearly, Mother Nature had two main concerns in evolving solid gait styles: how fast can we move and how energy-efficient is that movement. Especially for predators, if they expend more energy than they stand to gain by reaching the food, moving wouldn’t be worth it.
Although there are definite similarities between almost all quadrupeds’ gaits, each species adds its own flavor to them. Carnivores and herbivores both have strengths and weaknesses in considering optimal movement. Because digesting grass requires a lot of work, herbivores’ gastrointestinal tracts tend to be longer, with the consequence that their trunk has evolved to be quite rigid to sustain it, thus limiting the length and speed of their stride. To compensate, most herbivores have relatively long legs with feet that are designed mostly for running.
Horse Gait Animation Horse Walking Twelve Key Frames
Carnivores’ limbs, on the other hand, are usually multipurpose: for attacking/defending, climbing, and hunting. Their limbs are shorter in proportion to their body shape in order to increase control. In contrast to herbivores, carnivores don’t need extra energy to digest meat, so they have evolved a more flexible trunk that can open up the angle of the limbs and stretch the length of each stride, increasing the speed of the gallop.
Beyond that, every creature has a different stance; for example, while rabbits and mice tend to always keep their legs bent, heavier animals such as elephants would find that position exhausting. In mice, the energy cost is reduced and manageable due to their small size; it gives them the advantage of always being ready to jump and sprint at any moment, so the energy cost is negligible compared to the opportunity it affords. On the other hand, elephants barely bend their legs even when they are running and prefer to swing the legs like a pendulum. Different creatures have different needs.
Although these differences might sound trivial, they are worth considering in our analysis, and it is useful to understand the limits of each creature. Beyond the macro mechanical differences, there are anatomical similarities in the design of everyone’s legs that help us save energy and move around with freedom.
Figure 5 From Autonomous Animation And Control Of Four Legged Animals
“ An evolutionary path along which an animal species changed progressively, increasing fitness at every stage, would not necessarily lead to the fittest imaginable structure.”
Locomotion in animals is made possible by the combination of muscles and bones. While bones are the structure that supports us, muscles are the engine that gets things in motion, and like engines, they need fuel. Our fuel is composed mostly of carbohydrates and fats, and together with oxygen, it transforms into energy that can be used by muscle cells to contract and manipulate the skeleton. Because we need the energy to move and we need to move to get the energy we need, it’s not surprising that locomotion and nutrition are so tightly intertwined. For an animal to be fit, there has to be a fine balance between the energy it gets from eating and the energy it expends moving. How do we build a structure that can have the speed and flexibility we need while conserving as much energy as possible? For the most part, we compromise.
When we think about a mechanical design in nature, we must remember that we are working within the limits of the evolutionary process. That means that each successive step must be more useful than the previous; we can’t take a step back with the intention of taking two forward in the future. We can’t magically put all the pieces together in the proper place at one time—we always need to build gradually and only move forward.
Quadruped Anatomy For Animators
Evolutionary constraints partially answer the question of why we don’t all have wheels. Wheels seem the best choice; after all, they are very energy efficient, they function passively downhill and can keep a lot of momentum after the initial push. But if we take the time to get a closer look, we see that this argument falls apart rather quickly. Clearly, it would be almost impossible to create a freely rotating mechanism in the body using the system of bones and muscles that we already possess. Mechanically, it would be hard to set in place, even without considering the amount of friction and heat it would produce. We would also need to get to that result gradually, with every step of the way being useful.
But let’s say we could. Would it be worth it? Probably not. All the good attributes I listed about wheels are true, but only as long as we are either on man-made roads or relatively smooth terrain. The moment we found an obstacle in front of us, we would be in big trouble. With a bit of math, we can see that a wheel cannot climb an obstacle that is higher than the radius of the wheel itself. And forget about climbing trees or having a solid grip on branches. The alternative system that may not be as elegant as a wheel but can still minimize energy expenditure while giving us more versatility and freedom of movement works similarly to a spring.
Our muscles have incorporated spring-like systems that help us move around in an efficient way. The leg design is a versatile system that allows us to walk, run, jump, and climb. We move our bodies around by manipulating our skeleton like a puppet. Muscles move our bones in a lever system through contractions, and each muscle has a counterpart that can move the bone in the opposite direction. Muscles aren’t directly connected to bones; they attach to them through tendons, which offer a safety net to avoid overextending the muscle and help save energy. Muscles are very energy-hungry and, for the most part, depending on which type of lever is applied, can also be very energy-inefficient. We usually trade the extra energy used for explosive, fast movement.
A Guide To Quadrupeds' Gaits
Tendons’ role in locomotion is not to be underestimated though. Apart from connecting muscles to bones, they retain an elastic quality that in any gait helps recover some of the energy expended by the muscle to proceed to the next step, by extending when the limb is bent and compressing upon straightening the leg.
The kinetic energy produced by the muscles in the first part of the step is stored as elastic energy in the tendons to be used in the second part of each step. Contrary to muscle contraction, which is an active process and requires energy to fire off, the elastic properties of the tendons make them work passively. This dynamic is always present even though, depending on the type of gait, it comes into effect at different levels.
Quadrupeds can have different
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