The Porcupine has been a symbol used by Libertarians since at least the 1970s. The popular explanation has been that it is an animal that has weapons used only in defense (i.e., its quills) rather than in aggression as emblematic of the Non-Aggression Principle. The national Libertarian Party officially adopted the porcupine as its campaign emblem to be used similarly to the elephant and donkey on September 13, 2020.
Source