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There are a few works that have creatures in them that form some sort of ball out of themselves and then roll around in a much more willfull and directed manner than the rolling at the mercy of gravity kind of rolling that pillbugs and, if I remember correctly, some sort of dune spider is known for who prefers to roll down a dune than walk down it. While creatures rolling themselves up into a more or less round shape is a common occurence, what I want to know is if this sort of directed rolling locomotion is possible for creatures or even a viable way to get around.

My initial suspicions of how it might work is that they have a body-length organ filled with some sort of weight that effortlessly passes from one end of the organ to the other in a repeated controlled fashion like breathing that acts as a way for it to adjust its center of gravity in a way that in its rolled-up state it will begin to roll around but I just don't know if that sort of thing is possible/plausible or if creatures rolling around as if they were bowling balls with a mind of their own will firmly remain in the realm of fantasy.

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    $\begingroup$ Does tumbleweed qualify? $\endgroup$
    – alamar
    Commented Nov 3, 2021 at 19:37
  • $\begingroup$ Well, Moroccan flic-flac spiders should show that it is very much viable in a desert-like environment when you want to move fairly quickly. Taking a better look at those will definitely help you (fun fact, they can actually roll around willing and with a decent level of control, rather than depending on gravity all the time, though their rolling is closer to repeatedly doing front flips). $\endgroup$ Commented Nov 3, 2021 at 22:29
  • $\begingroup$ Rubrikon, please explain what you mean by "plausible." Plausible in Real Life? That's an off-topic question. Plausible on your world? Obviously the answer is yes because it's your world. Try to avoid asking things like "is this realistic" or "is this plausible" when what you should really be asking is "How could I make this happen?" (And you'll get better answers, "is this plausible" tends to get more "no, and here's why" answers.) Keep in mind that on a Stack that strives to suspend disbelief, whether or not something is plausible is irrelevant. Cheers. $\endgroup$
    – JBH
    Commented Nov 3, 2021 at 23:52
  • $\begingroup$ Chapter 11 of First Lensman (E.E "Doc" Smith, 1950) includes a description of the Zabriskan Fontema, a small rolling creature so amazingly unintelligent that it's used as an exemplar for the rest of the book series. $\endgroup$
    – user535733
    Commented Nov 4, 2021 at 2:36

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While it certainly is possible to roll, as many creatures do, there are some things you sacrifice while rolling. These issues are major strikes against the likelihood of a mostly rolling creature.

Firstly, these creatures lose a lot of sensory input. Their eyes and nose are covered, since a head gets tucked in, and hearing usually is impaired. This is not insurmountable. However, I would expect some improved sensory adaptations for determining range and distance of various things animals are interested in: prey, predators, and environmental hazards. These are easier to figure out when you are not constantly spinning and your head isn't near your butt.

Secondly, rolling is about harder to control and deals with natural environments poorly. Even small variations in the environment can send a rolling creature off course. Nevermind trying to overcome obstacles like large rocks or ditches. Unless you are going downhill, rolling is very energy intensive! You have to move your whole body at one time, bestowing both rotational and linear momentum to it, instead of just linear momentum from a few muscles.

Both of these issues make it quite likely that rolling remains an emergency, evasive maneuver instead of a main mode of transport.

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Yes, if in a city.

Rolling isn't very useful unless you have a hard surface everywhere.

When you roll on a soft surface, you get what is called rolling resistance. where all the energy you use to deform the surface is lost. This massively increases the amount of energy lost, and makes walking much more efficient. Cars and civilization have roads. Nature doesn't have roads.

Wheels handle wet weather and loose material badly.

Wheels tend to slip easily, and lose traction on loose soil. This means even if you have a hard surface you won't be able to use it well if it rains or if there's rocks around.

Wheels can't turn well or go over objects well.

Wheels have a much larger turning radius than legs. This makes going around things much harder. They also don't handle going over objects well, getting stuck at it or on top.

All this means that rolling as a primary locomotion method needs regular flat surfaces, no objects in the way, no sharp turns needed, and no regular rain.

So, just have a creature that evolved or was created in an urban environment, where we ensure there's lots of spaces like that for the sake of cars and wheel chairs.

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  • $\begingroup$ I get what you're saying about rolling resistance, but doesn't a paddle-wheel boat basically prove your issue moot? Whether or not resistance matters depends on how much energy is available to roll around. Proof of concept: walking through air and walking through water, which a human can do just fine until there's too much water. $\endgroup$
    – JBH
    Commented Nov 3, 2021 at 23:49
  • $\begingroup$ Animals have to move quickly and hunt and kill things for their food. Paddle wheel boats can rely on humans to fetch them coal and don't have to move quickly, and they were mostly only useful if the water was regular. $\endgroup$
    – Nepene Nep
    Commented Nov 4, 2021 at 10:14

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