Secret groove could be the secret to giraffe strong, skinny legs
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How do the spindly legs of a giraffe support its huge weight?
It's something that has puzzled scientists, but they may now have uncovered the answer.
Researchers at the Royal Veterinary College in London have identified a highly specialised ligament structure that is thought to prevent giraffes' legs from collapsing under the immense weight of the animal.
Researchers at the Royal Veterinary College in London have studied the legs of giraffes and found that they were able to withstand huge forces thanks to a distinct groove that runs along the length of their shins, housing a structure called the suspensory ligament. This structure is found in other large animals, such as horses
'Giraffes are heavy animals, around 1,000 kilograms (2,200 pounds), but have unusually skinny limb bones for an animal of this size' explained lead investigator Chris Basu, a PhD student in the Structure and Motion Lab.
DO KANGAROOS HAVE FIVE LEGS?
In other leg-related news, scientists looked at how kangaroos maintain their balance.
When foraging for food, these usually majestic creatures look ungainly and awkward as they attempt to balance their heavy bodies.
But now researchers have discovered that appearances may be deceiving, and their cumbersome movements are in fact helped by a fifth 'limb'; their tails.
Scientists from Colorado, Sydney and Burnaby in Canada discovered that a kangaroo's tail provide as much driving force as their front and hind legs combined.
'We found that when a kangaroo is walking, it uses its tail just like a leg,' said Associate Professor Maxwell Donelan of Simon Fraser University in in Burnaby, Canada.
'This means their leg bones are under high levels of mechanical stress.'
In giraffes, the equivalents to our metatarsal bone (in the foot) and metacarpal bone (in the hand) are extremely elongated, accounting for roughly half the leg length.
A distinct groove runs along the length of these bones, housing a structure called the suspensory ligament.
This structure is found in other large animals, such as horses - which are well known for their ability to sleep whilst standing - but this is the first time that it has been studied in giraffes.
The researchers hypothesised that this arrangement may help solve the mystery of how the giraffes' spindly legs can support its weight.
To test this, the researchers received donations of limbs from European zoos; these came from giraffes which had died naturally in captivity or been euthanised for reasons unrelated to this work.
The limbs were then fixed in a rigid frame and, using a hydraulic press, the researchers applied forces of up to 2,500 Newtons (around 250 kg), to simulate the bodyweight supported by each limb.
It was found that the limbs remained upright and stable without any additional support and could even withstand greater loads.
To test the strength of giraffe legs the researchers received donations of limbs from European zoos; these came from giraffes which had died naturally in captivity or been euthanised for reasons unrelated to this work. The limbs were then fixed in a rigid frame and subjected to large forces, equivalent to the weight of a giraffe
As the suspensory ligament is elastic tissue, and not muscle, it cannot generate force itself so can only offer passive support.
This means that giraffes can support their weight without actively engaging as much muscle, thereby reducing fatigue.
The suspensory ligament is also thought to prevent the foot joints from overextending and protect the feet from collapsing.
Mr Basu hopes that this information will help to explain how giraffes evolved from small, antelope-like species to the iconic long-necked animals we know today.
'I'd like to link modern giraffes with fossil specimens to illustrate the process of evolution,' Mr Basu said.
'We hypothesise that the suspensory ligament has allowed giraffes to reach large sizes that they otherwise would not have been able to achieve'.
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