A WildPose image of part of a herd of springbok with two (individuals 6 and 7) sparring. Photo credit: Naoya Muramatsu.
Most biomechanists would give their eyeteeth to get in close on the final instants in a dramatic pursuit, capturing each twist and turn of the manoeuvres as a predator closes in on its prey. Until recently, the only hope scientists had of capturing details of such a thrilling encounter would be if the animals were wearing GPS collars, and even then, the minute details of individual footfalls would be lost. Amir Patel (University College London, UK) had been studying the movements of captive cheetahs for more than a decade, but he wanted to know more about the animals in the wild, so he and Naoya Muramatsu (University of Cape Town, South Africa) wondered whether LiDAR could hold the key. ‘LiDAR is a laser-based 3D scanner that creates a detailed 3D map of whatever it scans’, says Muramatsu. Patel pitched the idea of combining the laser scanning technology with a high-definition camera to Google, and when they jumped at the chance to support the project, WildPose was born.
But first the duo had to identify a LiDAR system that would provide high-resolution 3D scans to complement their high-speed (170 frames s−1) high-definition camera – equipped with a state-of-the-art zoom lens to get in close, even when an animal was more than 100 m away. Muramatsu and Patel then spent 3 months assembling the sophisticated software that would control and direct the LiDAR and camera, simultaneously focusing on long-range animals, recording high-speed movies and collecting the lower speed (10 frames s−1) LiDAR scans. Then they tested the system, filming Muramatsu walking in circles, calculating that WildPose could locate his position to within ∼7 cm, even when he was 160 m away.
Eventually, Muramatsu and Michael Katsoulis (University of Cape Town, South Africa) headed to Kgalagadi Transfrontier Park, South Africa, with WildPose mounted on the door of their 4×4 vehicle, to film the creatures they encountered. ‘I was incredibly excited the first time I successfully recorded an animal using the system’, says Muramatsu, recalling the grace and beauty of the animals as he, Katsoulis, Nkabeng Mzileni and Corera Links (South African National Parks) filmed giraffes, lions, jackals, gemsbok and birds. However, operating the system in the harsh environment was challenging, with vibrations shaking screws loose, the system overheating in the sun and the colossal amount of disk space required to store the movies and 3D scans.
Back in the Cape Town lab, Muramatsu worked remotely with Sangyun Shin, Qianyi Deng and Andrew Markham (University of Oxford, UK) to analyse the recordings and successfully measured the height of a 5.5 m giraffe, which had been 90 m away, and a ∼50 cm tall martial eagle. Muramatsu also zoomed in on an individual red hartebeest, which had been captured sauntering away at an angle, successfully calculating that it was walking at 0.844 m s−1 and reconstructing the movements of its 0.82 m long legs. In addition, he followed the path of a springbok herd, revealing the first details of two individuals sparring; and the subtle chest movements of a lion reclining 31 m off, as its shallow irregular breaths settled to a rhythm of 80 breaths min−1. ‘WildPose enables observations of 3D movements of animals that have rarely been recorded outside of laboratory settings before’, says Muramatsu, although the team admits that there are some drawbacks, including the LiDAR's narrow field of view and tall grasses obscuring scans.
‘I believe that WildPose has the potential to revolutionise a wide range of fields, from animal health monitoring to engineering applications’, says Muramatsu, and he is keen to get back into the wild to reveal more about the movements and interactions of these enigmatic creatures in their natural surroundings with WildPose.
