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SPEED & METABOLISM CORRECTIONS
I'm not going to continue on this theme beyong this note, but some comments by
Troutman and others on speed, size and metabolism need to be addressed.
MT cited Auffenberg's data suggesting oras walk nearly 5 km/h. I asked
Auffenberg to send his data and he had none. My survey of many ora vidoes
shows they normally walk at reptilian speeds, 0.4-2 km/h. In more recent works
Auffenberg has cited similarly slow speeds for large monitors.
It is not their sprawling legs, which are as energy and physically efficient
as erect limbs, that prevents reptiles from often walking at high speeds. Nor
is it viable for reptiles to move as fast as mammals, but to do so for shorter
periods of time. No matter what their size of limb design, it is not possible
to animals with reptilian aerobic scope to forage or cruise at speeds
exceeding 0.1-2 km/h. To walk faster requires reptiles to use anaerobic power.
For various metabolic and toxic reasons the latter CAN ONLY BE USED FOR BRIEF
EMERGENCY BURSTS OF SPEED (attack or flight), it is never used to sustain
activity. My assertion that reptiles cannot sustain high walking speeds is
standard physiology documented by Bennett and others. The notion that animals
with reptilian aerobic scopes can walk as fast as mammals and dinosaurs is
sheer speculation, and so extremely implausible it must be rejected unless
The speed difference between mammals and dinosaurs (estimated from trackways)
on one hand and reptiles on the other is dramatic. Plotted out, almost all
reptiles sampled are below 2 km/h with peak speed below 1 km/h, almost all
mammals and dinosaurs above 3 km/h with peak speed 4 km/h. It costs four times
as much energy to walk 4 km raher than 1 km in an hour.
The concept, expressed by another list member, that dinosaur giants could walk
fast with reptile energetics is false. First, erect legs originally evolved in
small dinosaurs, and they had to evolve elevated aerobic capacity in order to
power the speeds their long striding legs were prone too. Sauropod descended
from such small dinosaurs. Second, even giant reptiles cannot sustain speeds
over 2 km/h, but giant dinosaurs regularly walked twice as fast.
Off tomorrow to see the new feathered Chinese dinosaurs at the National
Geographic. Looking forward to it!