Those that watched the spectacular BBC documentary series Planet Earth II may have marveled at the lengths the team went to embed themselves in the wilderness and capture such incredible moments in nature. For those that didn't, rest assured there were some sneaky tactics at play (plus a whole lot of waiting around). A new series airing on the BBC this week takes these efforts to a new level, deploying lifelike reptilian robots that walk and film freely among their living subjects.

The robots were built at Switzerland's École Polytechnique Fédérale de Lausanne (EPFL), the same research institute that has recently given us feathered aircraft, turtle-inspired drones and grasshopper-inspired robots. But it was the robotic salamander built by EPFL's Biorobotics Lab back in 2013 that caught the eye of BBC producers.

"We extensively work with robots to understand animal locomotion," Kamilo Melo, a scientist at EPFL, tells New Atlas. "Particularly, we work with salamander robots, which are one kind of sprawling posture animal. BBC Producer Rob Pilley approached us with interest to develop a crocodile version of our sprawling posture robots for his program."

So the team got to work designing and building not just the robotic crocodile, but a monitor lizard to go with it. This involved studying the animals' movements in order to recreate their walking mechanics, and using motors, aluminum and carbon fiber to imitate joints and bones. A small computer was embedded and hooked up to 24 motors that allows remote control up to 500 m (1,640 ft) away, and then finally the robots were wrapped in a waterproof latex skin.

The likeness is jaw-dropping. Equipped with cameras rather than eyes, the robots were able to get up close and personal with live creatures in their natural habitats in Uganda. While they helped the BBC get the footage they needed, they also double as a valuable research tool for the EPFL team.

"We learned many lessons, particularly the operation of our robots on the field, under different extreme conditions like humidity, dust and high temperatures," Melo says. "High temperatures (about 70 degree Celsius (158 °F) inside the crocodile robot latex skin) made our motors shut down frequently and our batteries to drain faster than we expected. This makes this whole adventure really useful for our own research."

The rugged landscape in Uganda can assist the researchers in developing future search and rescue robots in particular, which could be deployed in similarly hostile conditions following an earthquake, for example.

You can hear from Melo and see the robots do their thing in the video below.

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