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Re: surface/volume ratio and water loss in smallest amniotes

There is a lot of factors to consider when looking at this problem, none of 
which are overwhelming:

1) Total water budget of the ptero (can be easily estimated from its volume and 
then modeling either a lizard metabolism vs. a bird metabolism.
2) Surface area of the animal.
3) Stress load on the animal (water loss increases with greater physical 
stress.......model this with both a lizard's load and a bird's load).
4) Permeability of ptero integument (model various types...this part should be 
5) Flying with the air current vs. flying against the air current (see #3 
6) Velocity of the air over the body (this varies between curved surfaces and 
flattened surfaces).....best to model this on a computer.
7) Relative humidity (best to just use estimated average RH).

It is amazing that tiny invertebrate flappers can fly against the wind, but 
many do.  NOVA recently had a show on the migration of the Monarch butterfly.  
Truely amazing animals.

I wouldn't be surprised if theory (and experiment) suggests that there is no 
absolute boundary for the size/volume ratio of vertebrates, nor of the absolute 
minimum size of a vertebrate.


---------- Original Message ----------
From: "Richard W. Travsky" <rtravsky@uwyo.edu>
To: dinosaur@usc.edu
Subject: Re: surface/volume ratio and water loss in smallest amniotes
Date: Wed, 10 Feb 2010 21:19:06 -0700

On Wed, 10 Feb 2010, David Peters wrote:
> Speaking of 2/3, 3/4... [...]
> Would the lack of smaller birds/bats/pterosaurs be more of a flight 
> problem (too small for windy conditions or incoming rain drops)?

Out in the open seems likely.

If flying is done in forested areas then wind effects could/would
be mitigated somewhat.

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