Long Skinny Legs
Biology
Level
2
Why do large land mammals generally not have long, skinny, spindly legs insects typically have?
They retain heat using their thicker limbs (being warm-blooded)
They don't need long, flexible limbs to crawl into tight spaces as insects do
Large land mammals are tall enough as they are. They don't need extra height to reach their food
Because of the way an animal's strength-to-weight ratio scales as it gets bigger
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1 solution
The key here is that muscle strength and body weight scale differently.
The body weight is varies with the volume, which varies with the third degree of length, ∝ l 3 .
Muscle strength scales with the muscle diameter ∝ l 2 . This is because muscles are composed of fibre bundles (myofibrils), and as one would think, the muscles get stronger when there are more fibres, rather than when there are longer fibres.
So, if an ant were scaled to be ten times it's size, to make it as big as a dog, its mass would be 1000 times, but its strength only would have grown 100 times. To make this, work the scaled ant-dog would need 10 times thicker legs even after the initial scaling.
And, that's why land mammals do not have skinny legs.