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Gerard LeBlond for redOrbit.com – Your Universe Online
Giraffes are a tall, heavy animals weighing approximately 2,200 pounds with long, thin legs. So what keeps their legs from collapsing under their enormous weight? Researchers have apparently answered that question by identifying a special ligament structure on the leg bones of the creature.
“Giraffes are heavy animals (around 1000 kg), but have unusually skinny limb bones for an animal of this size. This means their leg bones are under high levels of mechanical stress,” lead investigator Chris Basu, a PhD student in the Structure & Motion Lab at the Royal Veterinary College, explains in a statement.
The giraffe’s bones, which are similar to the human metatarsal or foot bone and the metacarpal or hand bone, are elongated and make up about half the total length of the leg. Along the length of these bones are grooves which contain the suspensory ligament. Other large animals such as horses also have this type of leg structure, but this was the first time the giraffe has been studied.
This structure could explain why the giraffe’s legs can hold up their immense weight without collapsing.
To test the theory, researchers accepted donated limbs from European zoos. The legs came from already deceased giraffes who had died naturally or been euthanized for unrelated circumstances. The researchers placed the limbs securely in rigid frame and by using a hydraulic press applied about 560 pounds of force to each limb to simulate the bodyweight of the giraffe. The legs remained upright and stable even under added force. The suspensory ligament is a tissue, not a muscle, so its function is for support and cannot generate any force on its own.
Another benefit from this type of leg structure is that very little muscle is used to support the giraffe, so the animal will use less energy, reducing fatigue. The ligament is also believed to prevent the foot joints from overextending and it protects their feet from damage.
Giraffes are believed to have evolved from a small antelope-like creature and Basu hopes this new information will help explain this. “I’d like to link modern giraffes with fossil specimens to illustrate the process of evolution. We hypothesise that the suspensory ligament has allowed giraffes to reach large sizes that they otherwise would not have been able to achieve,” he said.
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