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Re: Scaling problems in Hutchinson 2004




MICHAEL HABIB wrote:

> To put it another way: perhaps a 40 ton sauropod could be built to run fast, 
> but really, what is the point?  Might as well reduce strain and put more 
> energy into making, say, a big belly.  To those on the list with expertise in 
> this area: is this reasonable?

Colin Pennycuick has done an interesting paper on maximum leg length suitable 
for running in a 1g gravitational field.  I don't remember the title offhand, 
but will post it when I find it.

> 2)  Are there any good references regarding scaling in aerial locomotion?  
> Presumably
>  size has an effect on acceleration (both linear accel and turning), top 
> speed, and relative speed in flying animals as well.  I'm particular 
> interested in refs on verts for this, anything on birds would be fabulous 
> (which, presumably, would be the bulk of that literature anyway).

Again, Colin has done some work in this regard.  His papers on flight 
performance in Whooper swans comes to mind.  One male specimen (JAP) is the 
largest individual bird of that species and is also the largest individual bird 
of any species known to fly by means of continuous flapping.  However, he is 
not as fast as some of the smaller females of his species.

> I find this (aerial scaling) to be less 'intuitive', in a way, because the 
> examples are not as easy to sort out.  Fast flying birds come from both 
> large-bodied and small-bodied lineages.  This could mean that small birds 
> that fly fast (like swifts) simply devote massive proportions of their bodies 
> to flight (which seems to be the case), but it might also imply that there 
> are tradeoffs that affect speed in both large and small taxa.

Continuous speed (as opposed to burst speed) in flying vertebrates is usually 
going to be primarily (but not totally) a function of wingloading and optimal 
CL (which is a function of planform).

>  For example, large birds presumably get more thrust per stroke, but they 
> also have to generate more lift (and may have to expend proportionally more 
> energy to recover strokes quickly).

I'm not quite sure what you mean by "recover strokes quickly".  If you are 
referring to the relative portion of the beat period that is spent in the 
downstroke versus the upstroke, that is generally chosen such that the specific 
power of the levitator muscles (Watts/gram weight of muscle) is about equal to 
that of the depressor muscles.