Re: Sauropod browsing energetics

[Don Ohmes <d_ohmes@yahoo.com>]

On 3/24/2011 8:53 PM, Scott Hartman wrote:
> Hold up.  A longer neck will almost always mean you can browse more
> bites per step.

Almost always? In all but the most specialized (and unlikely) habitat 
case (populated by plants that are spaced very widely *and* of a size 
such that the shorter necked animal can access the entire plant).

> That's not at all the same as saying you can take
> more bites (browsing) per unit time.

Sure it is. Shortnecked animals have to take more steps, and no animal I 
have observed can graze or browse effectively while in mid-step.

Considering two animals that browse at equal rate between steps, but do 
NOT browse during steps -- the animal that must take the fewest steps to 
maintain browse access definitely wins the harvesting contest...

Especially when you consider the likelihood in reality of both 
horizontal (in the case where substrate is less than ideal) and vertical 
areas of browse that the short-necked "multi-stepper" cannot reach.

> If resource allocation and neck
> speed motion is such that your long neck takes more time to sweep from
> one side to the other than it would take to just take a few steps then
> it's wrong.

Heh. You are speculating that a sauropod body could move it's head a 
given short distance by walking, in less time than it could by swinging 
the neck. That's OK w/ me, but all the people that say the mighty 
sauropods could kill theropods by clubbing those pitiful bipeds with 
devastating neckslams are not going to like it. If they hear about this, 
and you need a safe place to hide out, you can crash in my barn until 
things cool down...

> Furthermore, even if it's true in a given environment
> it's only energetically favorable if the costs of having the neck
> don't outweigh the increase in browsing rate.

Whatever the "24/7" costs of having a long neck were/are, long necks 
were and are energetically affordable to those that have them.

Given that elephants are known to need to forage as much as 22 hours a 
day to find enough food, and sauropods were much bigger than elephants 
(apparently because they *had* to be) -- it seems doubtful that 
*anything* outweighed an increase in absolute browsing capacity, in 
terms of evolutionary advantage accruing to certain morphological traits.

I still say the entire debate is a question in search of a problem, or 
perhaps more accurately a debate in search of a question -- it would 
seem to me that to establish a plausible speculation that long necks in 
giant herbivores are primarily a response to something OTHER than 
resource acquisition, it first must be established that increasing 
resource acquisition was/is not a critical problem on the path to 
giantism, and/or long necks were/are not useful in increasing total 
resource acquisition capacity.

Not going to happen...