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Re: "Cursoriality", etc.



> Date:          Sat, 27 Sep 1997 00:02:44 -0400 (EDT)
> Reply-to:      GSP1954@aol.com
> From:          GSP1954@aol.com
> To:            tons@ccs.netside.com
> Cc:            dinosaur@usc.edu
> Subject:       Re: "Cursoriality", etc.

> Michael asserts that elephants can fast walk (amble) well over 20 mph. This
> is simply not possible.

My information comes from direct observation and from several written 
sources as well as personal communication with the mammalian currator 
of the Columbia SC zoo(I don't know exactly what his doctorate is in 
but he finished at U of SC).  

>When an animal cannot achieve a suspended phase, and
> elephants cannot (even juvenile elephants doing the best they can cannot
> run), then speed is simply a function of stride length versus stride
> frequency. Although elephant legs are long, they have limited excursion arcs
> because they are so big. Maximum walking stride frequency is also limited by
> size. For an elephant to walk at 25 mph would require that its stride
> frequency be twice as high as possible.

I remember hearing that it was impossible for a bumblebee to fly, 
until reading a recent paper decribing the probable mechanism.  Some 
of my responses on line have a Zen quality to them.
> 
> I carefully timed an Asian elephant that won an elephant race in Thailand. It
> was the biggest bull in the bunch. It was obviously going full tilt. Speed
> was 12 mph. This is similar to the top speed Alexander observed chasing
> African elephants. They used film to measure the speed. Speedometer speeds
> are notoriously unreliable for a number of reasons and generally no longer
> used in scientific studies. As for humans being run down by elephants, most
> people cannot run very fast, especially on irregular ground. Able to achieve
> long suspended phases, most trained sprinters could easily outrun an
> elephant. Using antecdotal accounts of humans being squished by elephants is
> not a scientific way to estimate their speed. 

See the above comment.  However, observations in the field are not 
without any merit and not unusually contradictory.  That's where it 
all starts.  Most adult humans can run faster that 12 mph.  I have 
never seen anyone run down by an elephant.  Just making a point that 
if they can run faster than humans then they must be able to run 
faster than 12 mph. I do have a little personal experience with the 
animals;  you, no, I cannot run faster than a charging elephant.  And 
you're right about speedometers.  However, I will look into this 
more, since it never hurts to be skeptical.
> 
> Also note that energy efficiency is largely independent of speed at any given
> body mass. The dramatic increase of energy efficiency in hopping kangaroos is
> extremely unusual.

Agreed.  My point was that it happens in an extant animal.  Is it 
peculiar to their mode of locomotion (probably) or could it happen in 
theropods?  Did theropods hop? No, not tyrannosaurs!

>Bigger animals are relatively more energy efficient than
> smaller ones, recent measurements on elephants confirm this.

Locomotion is metabolically expensive.  Rate of oxygen comsumption in 
excess of basal rates increases linearly with velocity.  However, you 
are right in that energy utilization per unit weight for a given 
increment in speed is  less for larger animals. IOW, larger animals 
expend less energy to move a given mass a given distance. 
> 
> Finally, animals are excellent at accelerating. Rhinos reach top speed in
> just a few seconds. 

Agreed.

Michael