How lizards do a good ‘wheelie’

Some lizards can start running on two legs more quickly than others because of the way they move their bodies and tails, according to researchers in Queensland, Australia.

The scientists, led by Christofer Clemente, from the University of the Sunshine Coast, used a slow-motion camera to study eight species of Australian agamids, or dragon lizards, capable of the action known as bipedal movement – and often likened to a motorcyclist doing a one-wheel “wheelie”.

Biologist Nicholas Wu from the University of Queensland says the findings challenge the prevailing view that the backwards shift in the lizards’ centre of mass, combined with quick bursts of acceleration, cause them to start running on two legs at a certain point.

“What we found … is that some lizards run bipedally sooner than expected, by moving their body back and winging their tail up,” he says.

“This means that they could run bipedally for longer, perhaps to overcome obstacles in their path.”

In a paper published in Journal of the Royal Society Interface, the researchers suggest these dynamic movements during locomotion not only stabilise the bipedal strides, they also de-stabilise quadrupedal strides in order to temporarily switch to and extend a bipedal sequence.

Clemente says the results may have implications for the design of bio-inspired robotic devices.

“It’s been suggested that this movement might have something to do with increasing vision in moments of urgency, by elevating the head at the same time and helping to navigate over obstacles,” he says.

“Indeed, bipedalism would be advantageous for robots in specific habitats, for example, on open grasslands where, in nature, many bipedal running agamids are found.

“If obstacle negotiation is indeed improved with bipedal locomotion, then we have shown how the tail and body can be moved to enable it sooner and for longer. Maybe adding a tail to robots can help them go off-road sooner.”