Real animal data on ground reaction forces and kinematics were obtained from a previous study on the leg functions of desert ants Cataglyphis fortis24,25. The motion of the walking ants in an enclosed chamber was captured by a Photron Fastcam SA3 (San Diego, CA, USA) camera at a frequency of 500 Hz from the lateral and the dorsal view (Fig. 3). Their ground forces were recorded with a 4 × 4 mm force platform of resolvable forces Fx = 5.4 μN, Fy = 2.9 μN and Fz = 10.8 μN and natural frequencies of fx = 380 Hz, fy = 279 Hz and fz = 201 Hz26. The signals were amplified by a data acquisition system (MGCplus, Hottinger Baldwin Messtechnik, Darmstadt, Germany) and recorded with a sampling frequency of 1200 Hz. After each recording, the body mass was measured with an analytical balance of ±0.2 mg reproducibility (readout = ±0.1 mg, ABS 80-4, Kern & Sohn, Germany). A total of 274 trials with ground force measurements and video sequences were recorded for level locomotion. Trials in which the ants stopped, changed direction or touched the force platform with their gasters were excluded from the dataset. Subsequently, the first 15 records for each set of legs (front legs, middle legs, hind legs) were selected for data analysis resulting in 45 different strides. Besides the petiole, the head-thorax joint and the claws, the trajectories of the femur-tibia joint were additionally tracked for this study with Digitizing Tools 2016071127 and MATLAB R20015b (The MathWorks, Natick, MA, USA). To further model the joint torques, body parts such as the head, the thorax–petiole-coxae, the gaster and the femur-tibia-tarsi (legs) were weighed and photographed for 15 randomly selected ants.Figure 3Video screenshots of real ant locomotion. The red curve denotes the trajectory of body center, the yellow triangle represents the supporting triangle formulated by touchdown positions of stance feet while the blue arrows denotes the force vectors at the stance foot. (a) dorsal view. (b) lateral view.