By understanding which parameters influence an animal's locomotion, we might be able to define what a robot would have to look like and how it would have to move depending on what we want the robot to do: be super-fast, super stable, or something in the middle," Ms Schultz said. The orientation of their feet is not at all aligned with their direction of climbing," said Ms Schultz, who completed her undergraduate studies at the University of Bremen in Germany. Hong Kong SAR, Japan, Macao SAR, Malaysia, Philippines, Russia, Singapore, South Korea, Thailand, Vietnam, etc. Europe One set of animals where it is not clear how the differences between similar species arose is the lava lizard. Lava lizards live throughout the Galapagos archipelago and there are nine species in total. The different species are separated from each other geographically and have both different colouration and different push-up and head-bob behaviour that they use for communication. These results would seem to imply that there had been selection on lizards to not mate with other, similar species. However, the researchers also carried out a phylogenetic analysis which showed that the lizards had evolved these traits in isolation from one another and without much effect of sexual selection. So what’s going on? It seems that the lizards have evolved the ability to pay attention to the different behavioural signals of each other (and discriminate against the ‘wrong’ species) without having evolved in the same geographic area as them. Exactly how this happens is still not clearand perhaps just shows more than anything that evolution is complicated!

The researchers initially evaluated their robot in a series of simulations, to determine whether it could effectively replicate the movements of lizards. Their results were very promising, as they found that their robot could perform the desired motions and walking style. Dr. Clemente said that while the team had studied moving lizards for a long time, the robot allowed them to isolate and control the movements repeatedly to learn which way worked best. Like the researchers, both Xu and Morin have also worked on bioinspired color-changing materials in the past, using divergent approaches to imitate what the live animals still do best. Researchers in the field are still long ways off, says Xu, and he’s constantly in awe of the physiologies of these actively camouflaging creatures. By understanding which parameters influence an animal's locomotion, we might be able to define what a robot would have to look like and how it would have to move depending on what we want the robot to do: be super-fast, super stable, or something in the middle," Ms. Schultz said. The Mars rover can't get to a lot of places it needs to go because it's on wheels, but a legged climbing robot could access these areas," he said.They also found that the robot could climb the furthest when it combined limb movements with a side-to-side spine motion. But the spine could only flex around 50 degrees before the limbs had to move as well to increase stability. Although it could also move by solely rotating its spine, the most efficient movement came from large amounts of limb movement and small spine movements. The Mars rover can't get to a lot of places it needs to go because it's on wheels, but a legged climbing robot could access these areas," Clemente explained. Also, roboticists can apply concepts discovered in the researchers’ work. For example, using the findings from Goldman’s lab, roboticists have created snake-, lizard-, and amphibian-inspired robots that could one day be used in search and rescue operations. We were interested in why and how these intermediate lizards use their bodies and limbs to move around in different terrestrial environments,” Goldman said. “This is a fundamental question in locomotion biology and can inspire more capable wiggling robots.” The team then built a robot model to investigate the advantages of lizardlike and snakelike body movements in the intermediate lizard species. Known as a robophysical model, the robot functions as a physicist’s model of a living system that can also be used to vary parameters such as limb length and how the lizard’s body drags on the ground. With such capabilities, they can test the predictions of their theoretical model while also gaining understanding of the biological system.

Instead, Chong used a mathematical technique developed by particle physicists and control theorists in the last decades. While the theory, now referred to in the locomotion field as geometric mechanics, was initially introduced to study idealized locomotion — to understand how three connected points might swim in water — Chong adapted the theory to include the concept of legs.

Mimicking years of evolution to make climbing robots

Over time, as these differences between the two different populations become larger and there is less and less mating between the populations, they will become ‘reproductively isolated’ (i.e. not mating with each other at all) and thus become two new species.

Anole lizard (Anolis cristatellus) in the Caribbean National Forest in Puerto Rico. Credit: Terry Ord/UC Davis Ord and Stamps observed that "male lizards...advertise territory ownership to neighbors and intruders via dynamic visual displays consisting of species-typical headbobs and extensions of a colored dewlap." Sometimes, they begin their displays with exaggerated 4-legged push-ups before beginning the typical headbob sequence. As part of a larger study, Clark and colleagues investigated why it is that these differences in signals exist between the different species of lava lizard, in a paper published in Animal Behaviour. To do this, they designed robot lizards of two different ‘species’, Microlophus grayii and Microlophus indefatigabilis. The researchers used these robot lizards to simulate interactions between them and real lizards of the same two species. Therefore, a real lizard could either have an interaction with a robot of the same species, or of a different one. The idea here is, if different species have evolved to pay attention to each other’s signals (and thus avoid mating with a different species), then males that are the same species as the robot should respond much more to the robot’s signals than a lizard of the other species. On the other hand, if the different species arose by genetic drift, then we wouldn’t expect for there to have been as much selection on individuals to avoid mating with the other species. It has typically been thought that organisms either wiggle like snakes, bend like lizards, or use no body bending at all. When analyzing the footage, however, the researchers saw a wide variety of snakelike waves (traveling waves) and lizardlike movements (standing waves) represented across a diversity of lizard species.The best configuration for the climbing robot happened to be exactly what the lizards were doing, so the lizards themselves had already found the optimal gait for climbing," Ms Schultz said. Ord TJ, & Stamps JA (2008). Alert signals enhance animal communication in "noisy" environments. Proceedings of the National Academy of Sciences of the United States of America, 105 (48), 18830-5. PMID: 19033197 With the robophysical models, we can develop principles that can also inform the next generation of robots that might have to crawl around in rubble or move around in extraterrestrial environments like the surface of moons or planets,” Goldman said. The researchers found mixed results: M. grayii treated both robots the same, while M. indefatigabilis responded a lot more to robots that displayed more similarly to themselves (i.e. robots of their own species), responding both faster and then displaying for longer to the robot lizard.