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Re: Sauropod browsing energetics

On 3/23/2011 4:40 PM, Scott Hartman wrote:

P.S. As a smaller pet peeve; as far as I know it's universally
acknowledged amongst locomotion researchers that the cost of
locomotion goes down with size as a percent of your daily energy
budget (hence the "smaller than 1" scaling factor in the equation they
publish).  So why do they keep referring to moving the "enormous mass"
of sauropods, and keep citing size as a factor behind neck elongation
and browsing?  If "neck elongation and not walking" is going to be a
browsing advantage for anyone, it should be especially so for smaller
vertebrates who have to spend a larger amount of their daily energy
budget per unit distance moved.

There is a practical limit to the amount of biomass per unit area a given habitat can produce. If your absolute daily nutritional needs are higher than can be produced on the maximum area your mouth can access in a day, it really does not matter how cheaply you get by on a mass-specific basis.

An economic analogy would be -- 1) assume I weigh 1000 kgs, and can feed myself for a measly one dollar per kilo. 2) Assume you weigh 1 kg, and you have to spend 100$ per kilo to live.

I would seem to have a big advantage.

But if the maximum allowable daily wage is capped at 900$, I will definitely starve at the rate of 100$ per day, whereas you *might* not, even though your mass-specific expenses are much higher than mine.

This is why I think that "walking" vs "standing still" scenarios almost are not relevant when talking about very large animals and food acquisition -- when equal average velocity, mass and 'cutter heads' (i.e., cranial morphology) are given, long necks (or trunks) can simply access a larger area per unit time than short ones can.