US EditionGiraffes Evolved Long Legs to Save Energy, Not Just Reach Trees
Giraffes’ long legs raise the heart closer to the head, reducing heart energy use from 21% to 16% of resting metabolism, enabling their exceptional height, researchers say.
- Researchers at the University of Pretoria and the University of Adelaide found giraffes' long legs reduce blood pressure needed to reach the brain, saving a net 5% of energy intake.
- Fossil records show ancient giraffids lengthened legs before necks 16 million years ago, establishing an energy-efficient baseline for later neck elongation, Graham Mitchell explains.
- The model shows a 651 kg adult giraffe's left ventricle uses about 90.5 watts, based on MAP 214 mmHg, cardiac output 41.8 l/min, and cardiac efficiency ~22%, with heart energy at 16%.
- Long legs also create costs: giraffes face a locomotor penalty and must splay forelimbs to drink, lowering the heart ~0.48 meters and risking safety for hydration while saving about 1.5 tonnes of food per year.
- Pulmonary limits suggest the heart cannot sit more than about 35 centimeters higher without risking pulmonary edema, explaining why no taller erect-headed land animal evolved and why sauropod dinosaurs faced biomechanical ceilings.
11 Articles
11 Articles
How Giraffes Got Their Very Long Legs
Giraffes are best known for their elegant necks, stretching high over the savannah like periscopes. We have some pretty good ideas about why evolution granted them these long necks: access to the growing tops of trees, where some of the most nutritious leaves sprout, plus the longer the neck, the better a male giraffe is able to head bang his male competitors during mating season, a winning advantage with opposite sex. (These battles can get qui…
Evolution Gave Giraffes Long Legs First, And It May Have Saved Their Hearts
Those impossibly long legs that make giraffes look like they're walking on stilts aren't just architectural supports for a tall body. The post Evolution Gave Giraffes Long Legs First, And It May Have Saved Their Hearts appeared first on Study Finds.
Long legs reduce the energy requirement of pumping blood to the giraffe's head • This adaptation saves the animal more than 1.5 tons of food per year • Fossil evidence shows that legs evolved before the long neck
Coverage Details
Bias Distribution
- 100% of the sources are Center
Factuality
To view factuality data please Upgrade to Premium
