RE: "running" elephants

[John R Hutchinson <jrhutch@stanford.edu>]

Richard Forrest wrote:
There is a problem in considering elephants as models for dinosaur
locomotion:
A large elephant weighs 5 tons.
A large sauropod dinosaur weighed 80 tons - 16 times the weight.

To model the locomotion of a sauropod dinosaur on that of an elephant on
comparable top modelling the locomotion of an elephant from something
weighing about 300 kilos - a small horse, or a cow - which can do all sorts
of things elephants can't.
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I didn't see anything in my sentence about sauropods, or any other specific 
dinosaur, so I assume Richard is speaking in general to other 
persons.  I've worked on dinosaurs for quite a few years so I'm aware of 
the mass differences between larger sauropods and elephants, too.  (And 
also that some sauropods weighed much less than 80 tons, and some elephants 
can weigh more than 5 tons)   So of course I agree with the basic point.

[I should emphasize that our paper did not conclusively establish that 
elephants run; it is a preliminary report (hence the short paper) but I 
think it's very likely to be correct once we do the final work]

Additionally, I'm not a big fan of using particular extant animals as 
"models", analogs, or what have you for dinosaurs.  I prefer understanding 
the principles and mechanisms that make living animals work, and using 
multiple lines of evidence to see how those principles might apply to 
extinct animals.  I don't find analogs/models as very testable (even 
indirectly) or insightful.  They mostly head toward dead ends, not in new 
or fertile research directions.  [This is where I differ from what National 
Geographic's March article discussing my work said; it seemed to say that I 
see elephants as analogs for tyrannosaurs, which I actually do not but they 
thought it was vague enough]

IF elephants use a bouncing (biomechanically running) gait, such as Groucho 
running (a bouncing gait with more flexed limbs), the principle applicable 
to dinosaurs would be that even large dinosaurs might have been able to 
extend their range of locomotor performance by using a similar 
mechanism.  This is testable indirectly with computer models, etc.  Such a 
mechanism avoids an aerial phase and its impact on touchdown, has lower 
peak ground reaction forces, and is less jarring to the body (dampened 
propagation of forces throughout the body), but the downside is that it 
does not allow the same long strides and high speeds as running with an 
aerial phase, and it costs more energy per step because of the more flexed 
limbs.  We were a little surprised to find hints that elephants bounce, as 
we did not think that was a mechanism open to huge animals, especially 
elephants with their stereotyped columnar stance.  "Bounce" isn't a word 
often connected with elephants, but they do it (to a point).

Other points of potential dino-interest from the research includes the 
accurate measurement of near-max speeds in Asian elephants (15 mph), useful 
for those who think speed scaling methods for dinosaurs are useful, and the 
kinematic data (a huge set, 42 individuals and 188 trials, multiple strides 
per trial, wide size and speed range) are likewise useful for revising 
Alexander's trackway speed estimate equations, which badly need an 
overhaul.  And so on.  It's a preliminary report but we decided to publish 
it because there was a good fun story with a solid answer on speed and 
footfall pattern, it should stimulate more interest in elephants, and it 
promotes doing hands-on research with large animals rather than 
speculations, analogies, and anecdotes.

Cheers,
John



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John R Hutchinson
NSF Postdoctoral Research Fellow
Biomechanical Engineering Division
Stanford University
Durand 209, BME
Stanford, CA 94305-4038
http://tam.cornell.edu/students/garcia/.trex_www/naturepaper.html
http://www.stanford.edu/~jrhutch/fast_elephants/wanalee/index.html
(650) 736-0804 lab
(415) 871-6437 cell
(650) 725-1587 fax
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