View Full Version : A little question about animal size and strength

07-24-2008, 03:09 AM
I don't know how reliable my source was, but in an online discussion about Spider-Man, someone apparently mentioned that "the proportional strength of a spider" would actually be less than that of a human. This caused me some hesitation, because I have this idea for a character who can shapeshift into a wolverine. Except his mass doesn't change, so he transforms from a 150 pound man to a huge, 150 pound wolverine. That's about five times the weight of a regular wolverine, and my original idea is that he would therefore have five times the power a wolverine.

Maybe this is a dumb question, but could confirm whether or not I'm right in this? Wolverines are insanely tough for their size, and I kind of like the idea of a man-sized one wreaking havoc. :)

Elliot Cowan
07-24-2008, 03:15 AM
You are correct, yes.

07-24-2008, 03:58 AM
That's a tricky question. Strength does not increase proportionally with mass. A 600 lb Grizzly Bear is stronger than a wolverine, but not twenty times as strong.

And the standard comparison is that an ant can lift more than its own weight. But a giant ant would not even be able to support its own weight on its legs.

07-24-2008, 04:41 AM
You can kind of do whatever you want especially if you don't try to play Mr Science and use a numerical value for the shape shifter's strength. Just have examples of what he does do...peel the roof off a limo...bite a chunk out of a tire...but remember that wolverines eat til they are full and can digest bones certainly and maybe even teeth. It's been a while since I read about them.

As far as the spider thing and arguments like that, they make an awful lot of assumptions and if you follow the arguments to the logical conclusion they would assert that dinosaurs could never have walked, and obviously that's wrong. Humans have a different muscle recruitment than other animals. Without going into a whole dissertation on muscle and nerve physiology, we are built for endurance more than strength. A chimp could beat any same sized human in an arm wrestle (short burst of strength lasting seconds) but a human could out-do a chimp in shovelling coal over a day, in the wame way that a human can run further than a horse over a span of a week. We usually only get about 10% of muscle fibers contracting at any given time within a given muscle, but that 10% rotates around so that some muscle fibers are actually resting while those around them are contracting. If we could recruit the entire muscle (like in some disease states, medications and extreme emotional stress) we'd be able to do amazing bursts of strength, like lift a car off a child, (or pull the tendons off your own bones).

07-24-2008, 09:03 AM
It's the square-cube law in operation. In essence, as mass increases by the cube, strength only increases by the square. Let's say that you were 6' tall, could lift 200 lbs., and weighed 200 lbs. If you suddenly doubled in height, you could lift 800 lbs. (x4), but would weigh 1600 lbs. (x8).

All this means is that larger creatures, while lifting more, lift less in proportion in to their size. Thus, an ant lifts almost 20xits size, whereas an elephant only lifts about 1/4xits size.

So...your werewolverine may be able to lift a little more than an average human, but that's about it...


07-24-2008, 08:50 PM
Here is the Finnbars argument expanded:

If you take a cube and double the length of every side, you increase the volume by a factor of 8. In other words, the volume of an object varies as the cube of the change in dimensions. And since mass is proportional to density, then mass increases as the cube of the change in dimensions. So your double size cube is also 8 times heavier than your original. Or to simplify, to make something twice as large perform at the same level as it's smaller counterpart, the muscles will have to be eight times stronger.

That said, I honestly wouldn't worry about the physics. If your guy can transform into a wolverine, no one reading your story is going to care that the animal's muscles didn't get eight times larger. And if it is a 'magical' wolverine, since it is clearly not a normal wolverine, then it's muscles will be 'magical' too, won't they?


07-24-2008, 08:55 PM
It would very much depend on muslces position. An animals skeleton and musculature tend to maximise its strength for the scale it is. Therefore just increasing the size tends to decrease relative strength (i.e they may be stronger, but probably not 5 times stronger).

An ant the size of a human probably couldn't even stand up. Chimps are about our size but have 8 times the up body strength because they evolved as consistent brachiaters (swinging from arms) and we moved out of that environment so our muscle postion moved to be able to be more dexterous but as a result became less strong. There are a lot of trade offs.