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201223Jun19:49

How chee­tahs out­run greyhounds

Infor­ma­tion
pub­lished 23 June 2012 | mod­i­fied 05 Decem­ber 2012
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In a 060 mph stand off, most cars would be hard pressed to give a chee­tah a run for its money, and at their high­est recorded speed of 29m/​s (65mph) chee­tahs eas­ily out­strip the fastest greyhounds.

But, accord­ing to Alan Wil­son from the Royal Vet­eri­nary Col­lege, UK, there is no clear rea­son for the cheetah’s excep­tional per­for­mance. “Chee­tahs and grey­hounds are known to use a rotary gal­lop and phys­i­cally they are remark­ably sim­i­lar, yet there is this bewitch­ing dif­fer­ence in max­i­mum speed of almost a fac­tor of two”, he says. Team­ing up with Penny Hud­son and San­dra Corr, Wil­son decided to com­pare how chee­tahs and grey­hounds sprint to see if there were any mechan­i­cal dif­fer­ences between the two ani­mals’ move­ments and they pub­lish their find­ings in The Jour­nal of Exper­i­men­tal Biol­ogy.

Know­ing that cap­tive big cats are happy to chase a lure, the trio were con­fi­dent that they could get the chee­tahs at ZSL Whip­snade Zoo, UK, and the Ann van Dyk Chee­tah Cen­tre, South Africa, to sprint across force plates buried in a track in the ani­mals’ enclo­sure. The prob­lem would be get­ting the valu­able equip­ment to work in the open. “Force plates are cos­seted, loved pieces of equip­ment that peo­ple don’t gen­er­ally take out­side of the lab and bury in the ground in the Eng­lish sum­mer”, Wil­son chuck­les. How­ever, after suc­cess­fully installing eight force plates in the chee­tahs’ enclo­sure, along with four high speed cam­eras film­ing at 1000frames/​s, Hud­son tempted the chee­tahs to gal­lop along the track with a piece of chicken attached to a truck starter motor while she mea­sured the forces exerted on the ani­mals’ limbs, their body motion and foot­fall pat­terns. She also repeated the mea­sure­ments on gal­lop­ing grey­hounds back in the lab, film­ing the ani­mals at a slower 350frames/​s.

But, when Hud­son com­pared the ani­mals’ top speeds, she was sur­prised to see that the trained grey­hounds gal­loped faster than cap­tive chee­tahs, clock­ing up a top speed of 19m/​s com­pared with the chee­tahs’ 17.8m/s. Nev­er­the­less, Hud­son was able to iden­tify clear dif­fer­ences in the ani­mals’ stride pat­terns that could explain how wild chee­tahs would out­pace the dogs.

When run­ning at the same speed, the big cats’ stride was slightly longer than the grey­hounds’, although the chee­tahs com­pen­sated for this with a slightly lower stride fre­quency. Also, the chee­tahs increased their stride fre­quency as they shifted up through the gears – run­ning at 2.4strides/s at a leisurely 9m/​s, ris­ing to 3.2strides/s at their top speed of 17m/​s – whereas the grey­hounds main­tained a con­stant stride rate around 3.5strides/s across their entire speed range. Wil­son sus­pects that wild cats may be able to reach stride fre­quen­cies of 4strides/​s, which, in com­bi­na­tion with longer stride lengths, may allow them to out­strip their cap­tive cousins and hit top speeds of 29m/​s.

Also, when Hud­son analysed the length of time that each animal’s foot remained in con­tact with the ground – the stance time – she noticed that for some of the cheetah’s limbs it was longer, and the team sus­pects that this may be another fac­tor that con­tributes to the wild cheetah’s record per­for­mance. Explain­ing that increas­ing the stance time reduces the peak loads on the animal’s legs, Wil­son says, “[with] a longer stance time the chee­tah will get to the lim­it­ing load at higher speed than the greyhound”.

Spec­u­lat­ing about the rel­a­tively poor per­for­mance of the cap­tive chee­tahs, Wil­son sug­gests that they may lack motivation.

They have lived in a zoo for sev­eral gen­er­a­tions and have never had to run to catch food. They have prob­a­bly never learned to run par­tic­u­larly. The next stage is to try to make mea­sure­ments in wild chee­tahs in the hope of see­ing higher speeds
(Alan Wil­son, Royal Vet­eri­nary Col­lege, UK)

The above news item is reprinted from mate­ri­als avail­able at EurekAlert. Orig­i­nal text may be edited for con­tent and length.

(Source: EurekAlert, 21.06.2012; The Epoch Times, 21.06.2012)

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