Published: 25 Jan 2016 | Last Updated: 06 Oct 2017 09:26:24

Scientists from The Royal Veterinary College and Royal Holloway, University of London, have discovered the remarkable force and speed generated by the snake-hunting Secretary Bird.

The team measured the force and speed of a male Secretary Bird’s kick. The bird, called Madeleine, is housed at the Hawk Conservancy Trust, an awarding winning conservation charity, where it has been trained to attack a rubber snake, snakes being one of the bird’s favourite prey in the wild.

Sagittarius serpentarius Sekretär
Secretary Bird (Sagittarius serpentarius), picture taken at Serengeti National Park, Tanzania

The researchers found that the force generated by Madeleine’s kicks was 195 Newtons, equivalent to five-times his own body weight and enough force to kill its prey in a single strike. What was even more impressive about this unique hunting technique was the speed at which Madeleine can strike.

The time it took to kick the snake in the head was just 15 milliseconds (ms), faster than it takes to blink an eye. Dr Steve Portugal, a Lecturer at Royal Holloway University of London said: “The exceptionally rapid strike contact duration is 1/10th of the time it takes to blink an eye – which takes around 150ms”.

Madeleine’s demonstration of kicking a rubber snake (see video below) shows the bird’s unique and dramatic way of hunting, but it also provided the team’s researchers with the perfect way to measure the force and speed created by the bird’s mighty kicks. The research team placed hidden force-plates, which measure the pressure and impact of Madeleine’s strikes, under artificial grass and dragged the rubber snake across the plates. Each strike was measured for timing, speed and impact.

This combination of speed and force makes Madeleine, and all Secretary Birds, devastating and deadly hunters. However, such rapid time, coupled with the exceptionally long legs, means the birds are not using proprioception – the ‘sixth sense’ humans use to sense position and movement.

Therefore, the birds are using visual targeting and feed-forward motor control (pre-planned movements) when attacking their prey. This means the birds can only correct a missed strike in the next kick. Once they’ve started a kick, it cannot be adapted or changed and they have to wait for the next strike.

The consequences of a missed strike when hunting venomous snakes can be deadly, so the kicking strikes of Secretary Birds need extremely fast and accurate neural control. Delivering such fast, forceful and accurate kicks that can stun and kill prey requires precision targeting, demanding a high-level of coordination between the visual and neuromuscular systems.

Slow-motion video of Madeleine kicking the rubber snake

Beyond demonstrating the hunting prowess of the bird, these findings could also have wider, technological implications in areas such as robotics. Dr Monica Daley, a Senior Lecturer at the Royal Veterinary College explains: “There are interesting potential technological applications in ‘biologically inspired’ control of exceptionally fast movement in robots and prosthetics.  A comparable task might be playing baseball with a prosthetic arm, which requires very fast, forceful and accurate arm movements for pitching and batting”.

These findings will also helping scientists reconstruct the hunting techniques of the extinct, aptly named, terror birds and shed light on the movement of other more common birds.

Dr Daley added: “Despite their very unusual appearance with exceptionally long legs, the secretary bird’s striding gait is remarkably similar to of ground birds such as pheasants, turkeys and ostriches. This suggests that specialisation for their remarkable kick-hunting technique has not unduly compromised their locomotor abilities”.

The study has been published in the journal of Current Biology.

Paper reference: Portugal SJ, Murn CP, Sparkes EL and Daley MA (2016) The fast and forceful kicking strike of the secretary bird. Current Biology. 26, R1–R3, January 25, 2016

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