To figure out how dinosaurs walked, you could build an elaborate computer model… or you could attach a fake tail to a chicken’s butt.

Scientists from the University of Chile, the University of Chicago and the University of Illinois at Chicago opted for the latter approach in their research, as you can see here:

Modern birds descend from a group of dinosaurs called theropods, a vast suborder that includes both the 40-foot long, 7-ton Tyrannosaurus rex and the diminuitive Anchiornis huxleyi, which was little more than a foot long and weighed in at just under 4 ounces. It might be possible to glean some knowledge about the way theropod dinosaurs moved by closely studying their descendants. But, while chickens and dinosaurs have similar feet and feathers, there’s one key component missing in poultry -- the long, heavy tail.

So Chilean researcher Bruno Gossi and colleagues decided to fake it.

In the team’s experiments, four experimental chickens were raised from birth wearing an artificial tail made from a wooden stick, attached to the chicken’s behind with modeling clay. The researchers replaced the tail every few days as the chicken grew, keeping the tail at 15 percent of the bird’s weight -- a proportion they think is probably similar to the weight of a theropod dinosaur’s tail. They shared their observations on Wednesday in the journal PLOS ONE.

They found that the chickens raised with the tails walked differently and stood with a slightly altered posture than the control birds. The prosthetic-tailed chickens stood with their femurs (the big uppermost leg bones) held in a more vertically-oriented position, and moved their femurs and knees differently while walking:

Control chicken bone positions (no tail, no weight) shown in grey; control-weight chicken bone positions shown in yellow; bone positions for chickens with prosthetic tails shown in orange. Grossi et al/PLOS ONE

“These results indicate a shift from the standard bird, knee-driven bipedal locomotion to a more hip-driven locomotion, typical of crocodilians… mammals, and hypothetically, bipedal non-avian dinosaurs,” the authors wrote.

To ensure that it wasn’t just extra weight of the tail causing the changes, the researchers also had another control group of chickens raised wearing coats with lead weights held close to the chicken’s center of mass. When they crunched the numbers, the control-weight group’s posture and walking gait were pretty close to the control chickens that were raised without any lead coats or tails.

“Our experimental approach, although not perfect, was effective in displacing the [chickens’ center of mass] and recreating locomotor patterns expected in non-avian theropods,” the authors wrote. “Thus, we expect that careful phenotypic manipulation of extant birds can open new avenues of experimental investigation into unexplored facets of dinosaur locomotor mechanics and energetics, providing a more nuanced understanding of the relationship between form and function in dinosaur evolution.”

SOURCE: Grossi et al. “Walking Like Dinosaurs: Chickens with Artificial Tails Provide Clues about Non-Avian Theropod Locomotion.” PLOS ONE, published online 5 February 2014.