Description of the 4 data files: All files are tables into a text files and are comma delimited. The files “merus.txt” and “propodus.dactylus.txt” represent the superimposed coordinates for the raptorial appendages (the merus and the propodus/dactylus respectively). They include animal ID, appendage side, measurement replicates, centroid size, and X and Y coordinate for each landmarks and semi-landmarks. The file “individuals.informations.txt” includes the animal ID, the sex, the animal total body length and the strike force. Some animals do not have a strike force and have “NA” instead. The file “” includes all the data relative to the spring section of the article. This is the sex of the animals, the spring force when maximally contracted, the spring stiffness, the animal total body length, the centroid size and the superimposed coordinate (X and Y) for each landmarks and semi-landmarks.