In line with Sustainable Development Goal 9 (sustainable industrialisation and innovation), environmentally responsible engineering designs in modern robotics should consider factors such as renewability, sustainability, and biodegradability. The robotics sector is growing at an exponential rate, and as a consequence, its contribution to e-waste is a growing concern. Our work contributes to the technology development of caninoid necro-robots, robots that are built from the skeletons of deceased dogs. The already formed skeletal structures of deceased dogs (and other animals) are ideal natural material replacements for synthetic robotic architectures such as plastics, metals, and composites. Since dog skeletons are disarticulated, simple but effective methods need to be developed to rearticulate their bodies. The canine skull is essentially a large end effector, but its mandible is held together by a fibrocartilaginous joint (symphysis) that degrades at a higher rate than the bone itself. The degradation of the symphysis would ordinarily negate the utility of a canine skull as a necro-robotic end effector; however, in this research, we consider simple methods of mandible reinforcement to circumvent this problem. Our research uses 3D scans of a real canine skull, which is modelled using the finite element method to ascertain optimal geometrical reinforcements for the mandible. The full skull structures and their reinforcements are printed and adhesively connected to determine the most effective reinforcing strategy for the mandible. Here, we elucidate geometrically selected reinforcement designs that are evidenced through mechanical testing, to successfully increase the stiffness of a disarticulated mandible.