Re: tyranno scavenging issues

[Jura <jura@reptilis.net>]

GSP wrote:
>The researchers use a speed of about 1.5 km/h as the foraging speed for a 
>reptilian tyrannosaur. This is actually reasonable for reptilian energetics, 
>and is superior to past studies that try to attribute unsustainably fast 
>walking speeds to reptiles. However, the way they estimate a reptilian 
>walking speed as a fraction of top speed is spurious. Sustainable walking 
>speed is not related to top speed. Tortoises can walk at speeds not much 
>lower than those of lizards than can run far faster. It is dependent upon 
>aerobic exercise capacity, which is very  low in all reptiles of all sizes, 
>so a reptilian tyrannosaur would not have been able to forage at speeds 
>exceeding 2 km/h. 

=========================================

While I agree that sustainable walking speed is related to aerobic capacity, 
the statement that aerobic capacity is low in reptiles of all sizes is false. 
While many extant reptiles suffer from a carrier's constraint issue that limits 
aerobic endurance (an anatomical issue, not a thermophysiological one), there 
are some groups that have found ways around it. Most are scleroglossans (teids, 
varanids, scinks). For these animals, assumptions of 1.5 km/hr are far too low. 
Auffenberg has observed normal foraging speeds of oras to be 4.8 km/hr, which 
is roughly twice as fast as you give them credit for. Along with Auffenberg, 
work by Bennet, Garland, Gleeson and others have shown high stamina in a 
variety of scleroglossans. So there are a fair amount of exceptions to the low 
aerobic reptiles rule.

Jura

======================================================

"I am impressed by the fact that we know less about many modern [reptile] types 
than we do of many fossil groups." 
- Alfred S. Romer  Osteology of the Reptiles

http://reptilis.net