North American porcupine (Erethizon dorsatum), Amistad National Recreation Area, 2015.

This rodent may have as many as 30,000 quills on its body, including everywhere except on its stomach. Quills are hairs with barbed tips at the end, solid at the tip and base but hollow for most of the shaft. The porcupine is not an aggressive animal but will use its quills to protect itself. Contrary to popular belief, a porcupine cannot shoot its quills. Instead, if a predator or other threat approaches the porcupine, it will turn its back, raise its quills and lash its tail toward the predator as a warning. If the animal is hit by the qills, the quills will become embedded in the animal's body. Amazingly, body heat causes the barbs to expand and they become even more deeply embedded in the would-be predators skin!