He's been stalking his prey for hours and it's all been boiling down to this moment. He crouches down and tenses his muscles, ready to attack and claim his prize. He dashes forwards towards the herd of gazelle, who instinctively turn and run from the imposing danger, and the chase begins.
Although the cheetahs (Acinonyx jubatus) have earned the title of "Fastest Land Animal" they actually rely heavily on their impressive flexibility and grip to give them monumental acceleration, deceleration and manoeuvrability. Whilst their straight line speed is still impressive, clocking in at around 35mph (or 56kph) on average but up to 58mph (93kph) on the very fastest sprints1, this pales in comparison to the world's fastest known animal: the Peregrine Falcon.
The peregrine falcon, or Falco peregrinus, can be found on every continent, aside from Antarctica, and puts the cheetah to shame with speeds of 200mph (320kmph) during a hunting dive, or stoop. It's these speeds that allow the falcon to hunt smaller birds such as sandpipers, pigeons and small duck, most often taking them out in mid-air assaults2. One bird has even been clocked at 242mph (390kph) in an experiment involving miniature altimeters and a lot of jumping out of planes3.
So how does the peregrine falcon achieve these astonishing speeds? The falcons pick up speed by beating their wings and then move into an attack position, decreasing wingspan by folding in their wings and angling down into a near vertical dive. This motion decreases the drag and removes the lift coefficient on the bird and the falcon accelerates rapidly4.
These incredible speeds allow the peregrine falcon to intercept prey in mid-air and stun or them before overtaking and instantly turning around so that the victim falls helplessly into the falcon's grip. In order to fly at these tremendous speeds the falcons have evolved bony tubercles inside their nostrils to disrupt the flow of air entering the bird's lungs, as the pressure caused by the dive would damage them5. The falcons also have special covers called nictitating membranes on their eyes to spread fluid and clear anything which might enter the bird's eye during the attack6.
But how do you stop yourself when you're hurtling towards the ground at over 200mph? To accomplish this, the falcon extends its wings to create drag; however the bird can only extend its wings to just over a tenth of the maximum wingspan, any further and the falcon could injure itself due to the force on the shoulder joints. The falcon must then allow sufficient altitude to pull out of the dive; predictions from one theoretical model say that a 1kg bird in a vertical dive would need a minimum of 60m to level out4.
When the falcon does pull out from the dive it undergoes intense deceleration; calculations on the data taken from Frightful, a falcon weighing nearly 1kg, catching a 0.9kg lure (similar to the weight of an adult duck) showed that Frightful experienced a whopping 27Gs, which translates into her feeling 27 times the normal weight of her and the lure, or 50 times her own weight3. In this situation the bird is twice as heavy and so needs twice as much altitude to pull out of the dive.
Unfortunately the numbers of the peregrine falcon fell sharply during the 1950s, 60s and 70s due to the widespread use of DDT and other chemical pesticides however since the use of such pesticides has been regulated the number of falcons has risen again and many populations are booming thanks to help from captive breeding programs7.
The peregrine falcon's tremendous speed and mind blowing agility make for a formidable combination and so whilst the cheetah may well be the fastest thing on land, the only way they'll win any race against a peregrine is if they break the rules.
1 A. M. Wilson, J.C. Lowe, K. Roskilly, P. E. Hudson, K. A. Golabek & J. W. McNutt (2013) Locomotion dynamics of hunting in wild cheetahs. Nature. 498: 185-192
2 Peregrine Falcon (Falco peregrinus) fact sheet. Conserve Wildlife Foundation of New Jersey. [Accessed 03/09/13] www.conservewildlifenj.org/downloads/cwnj_23.pdf
3T. Harpole (2005) Falling with the Falcon: Air & Space magazine [Accessed 02/09/13] http://www.airspacemag.com/flight-today/falcon.html?c=y&page=1
4 Tucker, V. A. (1998) Gliding flight: Speed and acceleration of ideal falcons during diving and pull out. Journal of Experimental Biology. 201:403-414
5 Falcons – Wildlife Notebook Series: Alaska Department of Fish & Game [Accessed: 03/09/13] www.adfg.alaska.gov/static/education/wns/falcons.pdf
6 Schwab, I. R. & Maggs, D. (2004) The falcon's stoop. British Journal of Opthamology. 88: 4
7 Falcon Populations: The Centre for Conservataional Biology [Accessed 03/09/13] http://www.ccbbirds.org/what-we-do/research/species-of-concern/peregrine-falcon/falcon-populations/