London, July 4 (IANS): Ever wondered how a giraffe's thin legs support its massive 1,000 kg weight? Credit it to a special ligament, new research says.
"Giraffes are heavy animals (about 1,000 kg), but have unusually skinny limb bones for an animal of this size," explained lead investigator Christopher Basu, a PhD student at the Royal Veterinary College in London.
"This means their leg bones are under high levels of mechanical stress," Basu added.
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 used limbs of dead giraffes donated by European zoos, fixed them in rigid frames and applied pressure to simulate bodyweight.
They found that the limbs remained upright and stable without any additional support and could even withstand greater loads than the giraffe's weight.
Ligaments are elastic tissue, and can only offer passive support. This means that giraffes can support their weight without engaging as much muscle, and do not get tired as soon.
This information will help to explain how giraffes evolved from small, antelope-like species to the long-necked animals we know today, Basu said.