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Re: "Cursoriality", etc.



GSP1954@aol.com wrote:
> 
> Michael asserts that elephants can fast walk (amble) well over 20 mph. This
> is simply not possible. 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 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.

I'll point out that races are even worse than speedometers for timing
running paces of animals, mostly due to the fact that animal behaviors
are much different in captivity than in the wild.  I'll also point out
that "obviously" doesn't carry any weight at all.

Kingdon's work, which formed a large portion of _East African Mammals_
and was reprinted in _Walker's Mammals of the World_, disputes your
statements above.  He gives a normal fast pace for African elephants as
10-16 kph, while a charge may reach 35-40 kph.  The charge speeds equate
to 21-25 mph.  If Alexander's work is published, current (post 1979, the
publication date of EAM), and uses a large sample size I'll buy it, but
unless that's the case I'll go with Kingdon's estimates (largely because
the works which use them are among the most solid and influential works
in mammalogy today).
 
> 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. Bigger animals are relatively more energy efficient than
> smaller ones, recent measurements on elephants confirm this.

Very true.  The efficiency of a mouse compared to an elephant is just
atrocious; however, mice only need a few ounces of food a day . . .
 
> Finally, animals are excellent at accelerating. Rhinos reach top speed in
> just a few seconds.

Yup.  Once you get past that initial inertia momentum helps you a *lot*.
 
Chris