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Re: ora speeds



>"Jura" posted the assertion by Auffenberg that oras  > regualry walk at nearly 
>5 km/h. But when I asked    > Auffenberg for his data set he said he had lost 
>it. > It is not possible for an animal with such a low aerobic exercise 
>capacity to sustain such speeds.

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A couple things:

1) Auffenberg's observations agree with those of another study:

Lederer, G. 1942. Der Drachenwaren (_Varanus komodoensis Ouwens). Zool. Gart. 
(Leipzig)(n.s.) 14(5/6): 227-244 

If I remember HP David Marjanovic correctly, these measurements were taken from 
animals at a zoo. Yet, they still represent an independent account of these 
animals moving at these speeds. If one doesn't mind translating German (better 
if one already knows German), then one might find a data set there.

2) Oras, and varanids in general, DO NOT possess low aerobic abilities. They 
are highly aerobic lizards (though degree of aerobiosis varies between species; 
much as it does in mammals).

Bennet(1972) was one of the first to show this. He compared _Varanus gouldii_ 
to _Sauromalus hispidus_. He found the monitor to consume twice as much oxygen 
as the iguanid, have a much lower lactic acid build up, and recover from 
exercise 3 times as fast under high temperatures.

Later work (Hopkins et al, 1995/Frappell et al, 2002) showed that, not only do 
monitors show gas exchange abilities on par with mammals, but their aerobic 
limitations are exactly the same as the ones found in mammals.

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> I timed a large sample of oras from videos and found 
> that they move at a typically reptilian pace of 0.5-> 2 km/h. 

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How, exactly, does one go about doing this?

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> When they move at 5 km/h they are hauling, usually  > in response to a 
> stimulus such as a carcasse 
> or combat.

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While I usually avoid citing nature documentaries when I can, if one watches 
the Komodo dragon special of The Crocodile Hunter, one can watch an ora 
trotting along at 8 km/hr (according to Steve Irwin). The animal appears very 
nonchalant in its movements (none of that muffled machinegun stuff), and while 
Steve was winded by the time it stopped, the ora showed no signs of aerobic 
distress.

Furthermore, Auffenberg's data (which shows 8-10 km/hr trots to not be 
uncommon) has shown that these animals are capable of speeds between 14-18 
km/hr. Now if an ora is "hauling" at only 5 km/hr, then it must be dying at 18 
km/hr.

In a separate post you mentioned that oras achieve their speed by anaerobiosis. 
This would be in contrary to data compiled on locomotion for these animals (no 
undulations at high speeds), and with data on behaviour during intense activity 
(killing and eating its own weight in wild boar in 17 minutes without 
exhaustion), all of which show them to be aerobic animals. Furthermore, studies 
on other monitors (Bennett 1972) show reliance on anaerobiosis only at very 
high temperatures. So, where are you getting your data about them be anaerobic?

Jura

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"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