A new research has suggested that long-necked dinosaurs didn't graze treetops, and were better off holding their necks horizontal, not upright.
According to a report in National Geographic News, lifting long necks at steep angles would have put intense pressure on sauropod hearts, requiring dramatic expenditures of energy to keep blood pumping to the brain.
Sauropods were giant, long-necked, long-tailed, four-legged plant-eaters that lived about 200 to 66 million years ago (prehistoric time line).
Since long-necked modern animals, such as giraffes, tend to browse on leaves in tall trees, paleontologists have assumed that sauropods-whose necks could be as long as 30 feet (9 meters)-must have done the same.
But, Roger Seymour, of the University of Adelaide in Australia, found that sauropods would have spent as much as 75 percent of their bodies'' energy to keep their heads held high.
Most mammals use about 10 per cent of their energy to circulate blood through their bodies. Giraffes use about 18 per cent of their energy to keep blood moving through their long, upright necks.
"Would the increased availability of food in tall trees be worth the cost? This seems doubtful," Seymour said. "It would probably make more energetic sense for (sauropods) to feed with their necks close to horizontal," he added.
By moving their necks side-to-side horizontally, sauropods would have been able to feed on a very large area of plant material without having to move their bodies.
That may not seem like a much of an energy-saving tactic.
But, in animals that may have weighed 30 to 40 tons, the energetic difference between taking a few steps and not taking a few steps may have been as huge as the animals themselves.