Animals like mountain bighorn sheep and muskox compete for mates and social dominance by slamming their heads together with massive force. Scientists had wondered how they could do this without damaging their brains. It turns out they can’t, as a new study has shown the animals can have brain trauma similar to that found in humans with chronic traumatic encephalopathy, which results from repeated head injuries. The research was led by Dr. Nicole Ackermans from the Icahn School of Medicine at Mount Sinai, who collected brain samples from the US Fish and Wildlife Service, and found damaged neurons “like a spiderweb growing across the microscope,” inside the animals’ brains. The work was published in Acta Neuropathologica.