I think everybody would agree that the cheetah is the fastest animal, at around 70 mph = 31 m.sec-1. But I was wondering which was the fastest relative to body size.
I've just calculated that the cheetah at a size of (say) 140 cms has a maximum speed of 22 m.sec-1.metrebodylength-1.
This question came into my head because a spider just ran across my desk, at a speed of at least 0.5 m.sec-1. Not that fast really, except that I estimate its size at 3mm before flattening (I have quick reactions, and besides, it came back again). Relative to body size, this makes 166 m.sec-1.metrebodylength-1, eight times faster than a cheetah.
Fleas don't qualify because they jump. But can anybody think of an animal that runs faster than my spider before it became an ex-spider?