Tuesday, 18 June 2013
Cheetah on hunting
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june 14, 2013 — Researchers at the
Royal Veterinary College have captured the first detailed information on the
hunting dynamics of the wild cheetah in its natural locale. Using an innovative
GPS and motion sense collar that they designed, Professor Alan Wilson and his
team were able to record remarkable speeds of up to 58 miles per hour (or 93
kilometers per hour).
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The results, from the
team at the Royal Veterinary College's Structure & Motion Laboratory, are
published June 13, 2013 in Nature.
To date, measurements of
cheetah locomotion mechanics have only been made on captive animals chasing a
lure in a straight line, with few studies eliciting speeds faster than racing
greyhounds. For wild cheetahs, estimates of speed have only ever been made from
direct observation or film, in open habitat and during daylight hours.
The team, led by
Professor Wilson, developed a tracking collar equipped with a GPS component and
electronic motion sensors (accelerometers, magnetometers, gyroscopes) capable
of delivering processed position and velocity data and sensitive to the
animal's movements. The collar was powered by a combination of solar cells,
rechargeable and non-rechargeable batteries.
Collar software monitor
the accelerometers to create activity summaries and detect the brief hunting
events and adapted collar operation to battery voltages and time of day,
meaning that researchers only captured data during a hunt. Overall, researchers
recorded data from 367 runs by three female and two male adult cheetahs over 17
months. An episode of feeding after a run indicated hunting success, and was
identified in the activity data by consistent, low-magnitude acceleration.
Data revealed that wild
cheetah runs started with a period of acceleration, either from stationary or
slow movement (presumably stalking) up to high speed. The cheetahs then
decelerated and manoeuvred before prey capture. About one-third of runs
involved more than one period of sustained acceleration. In successful hunts,
there was often a burst of accelerometer data after the speed returned to zero,
interpreted as the cheetah subduing the prey -- in this case mainly Impala,
which made up 75% of their diet.
The average run distance
was 173m. The longest runs recorded by each cheetah ranged from 407 to 559 m
and the mean run frequency was 1.3 times per day, so, even if some hunts were
missed, high speed locomotion only accounted for a small fraction of the
6,040-m average daily total distance covered by the cheetahs.
The team was also able
to identify factors that make up a successful hunt. Successful hunts involved
greater deceleration on average, but there was no significant difference in
peak acceleration, distance travelled, number of turns, or total turn angle.
This indicates that outcome was determined in the final stages of a hunt rather
than hunts being abandoned early to save energy or reduce risk of injury, and
the higher deceleration values may reflect actual prey capture.
The greatest
acceleration and deceleration values were almost double values published for
polo horses and exceeded the accelerations reported for greyhounds at the start
of a race. The acceleration power for the cheetahs was four times higher than
that achieved by Usain Bolt during his world record 100 metres run, about double
that for racing greyhounds and more than three times higher than polo horses in
competition.
Grip and
manoeuvrability, rather than top speed, were shown to be key to hunting
success. Hunts involved considerable manoeuvring, with maximum lateral
(centripetal) accelerations often exceeding 13ms-2 at speeds less than 17ms-1 (polo horses achieve 6ms-2).
Professor Alan Wilson,
said: "Although the cheetah is recognised as the fastest land animal, very
little is known about other aspects of its notable athleticism, particularly
when hunting in the wild. Our technology allowed us to capture what to our
knowledge is the first detailed locomotor information on the hunting dynamics
of a large cursorial predator in its natural habitat and as a result we were
able to record some of the highest measured values for lateral and forward
acceleration, deceleration and body mass.
"In the future,
equivalent data for other wild cursorial species would enhance what we know
about natural speed, agility and endurance, and provide detailed information on
ranging behaviour in the wild. For example, information on habitat selection by
endangered species detailing where animals are commuting, hunting and resting
would be informative when attempting to evaluate wildlife-protected areas."
The cheetahs used in
this study were part of a continuing study by Botswana Predator Conservation
Trust in the Okavango Delta region of Northern Botswana.
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