Animals employ a wide array of defensive strategies to avoid being killed by predators. Many taxa bear sharp spines that serve a variety of defensive (and non-defensive) functions including preventing biting and grabbing, hindering swallowing, and resisting extraction. The morphology and overall robustness of defensive spines vary across taxa from long and thick (echidnas and porcupines) to short and thin (tenrecs and hedgehogs). This talk will explore the ecological, physiological, and behavioral factors that promote the evolution of spiny defenses as well as explore other traits that may evolve with spines in a correlated fashion. These may include aposematic warning coloration, locomotion style, metabolic rate, and diet. The function and evolution of spines will be compared to that of plate-style body armor (e.g., armadillos), and a general summative framework will demonstrate how the integration of evolutionary and biomechanical studies of spines can help us better understand the selective factors that shape them.