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Re: Sauropod browsing energetics



2011/3/23 Scott Hartman <skeletaldrawing@gmail.com>:
> they
> aren't figuring in the extra cost of having the long neck (e.g. M is
> held constant)!  All that extra tissue in the neck has to be grown and
> maintained like any other part of the body;

At equal mass, the cost would be the same in a long-necked animal than
in a short-necked one, for the latter would have to maintain an
equivalent mass in other parts of the body.

> plus mechanically speaking
> simply having the longer neck necessitates greater muscle exertion
> _all the time_ (less so if held upright, but still extra work
> regardless),

At equal mass, wouldn't be necessary also greater muscular exertion to
support an equivalent mass in other parts of the body of the similarly
massive animal? (however, I cannot say which would require more - may
nuchal tendons not help supporting a long neck? may not relative head
reduction somewhat diminish the proportional increase in this effort?)

> The real question
> should be "what is the extra cost to maintain that longer neck 24/7
> (and also how it impacts survival to reproductive age) and whether
> THAT cost is lower than the energy saved while browsing with a longer
> neck?"
>
In addition, we should assess which animal of equal mass required more
energy to harvest a given area: if one moving a long neck and walking
relatively less, or other walking more with a short-neck.

> 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.
>
As Don says, this may hold unless we also consider the absolute amount
of energy employed (greater always in the larger animals), and the
capacity of the production of the ecosystems in the range of
distribution of the species in providing enough energy for a
sustainable population of large herbivores with those energetic
requirements.