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Shrikes, dubbed 鈥渂utcher birds鈥� because they impale their dead prey on thorns, can kill animals larger than themselves 鈥� and now we know how. High-speed camera footage of captive shrikes in action shows that they use their beaks to powerfully grip prey animals by the nape of the neck before flinging them around so fast that they instantly suffer fatal whiplash injuries.

鈥淭he speed that the shrikes turn their heads when they鈥檙e doing this is around the speed of the slow cycle of your washing machine, which is still pretty fast,鈥� says Diego Sustaita of California State University in San Marcos, and head of the team investigating the birds. 鈥淭hese g-forces are similar to those experienced by the heads of victims of rear-end car collisions that can cause whiplash.鈥�

Sustaita and his colleagues found out how loggerhead shrikes kill their prey by using a high-speed camera to film the birds killing mice. The shrikes were being 鈥渢rained鈥� for release into the wild on California鈥檚 San Clemente island, so no mice were fed to the shrikes solely for the research.

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By tracking landmarks on the bird鈥檚 head and the mouse鈥檚 body, the researchers were able to see how the two creatures moved relative to each other during the fatal encounters, which typically lasted just a few seconds. They found that the motions of the mouse鈥檚 head and body progressively became shifted out of phase, inflicting potentially fatal compressive forces on the neck bones.

Flung round with a force six times that of gravitational acceleration, the mice died through the inertial forces on the neck created by their own body spinning round.

This, says Sustaita, explains how shrikes are able to kill animals up to twice their own body weight, including lizards, small birds and snakes. 鈥淭he prey don鈥檛 become beheaded鈥�but our calculations and other research on whiplash suggests it causes damage to bones, muscles, ligaments and likely the spinal cord itself,鈥� he says.

Sustaita says that crocodiles, lizards and other birds and mammals are also known to shake their prey, often from side-to-side or smashing it against a hard surface. But he says the shrikes鈥� trick of spinning them round to kill by whiplash appears novel.