After mating, the female repels the male and a copulation plug is formed. The gestation period lasts between 205 and 217 days with the young being born from April to June. Offspring are precocial with open eyes when born. Senses of smell and hearing develop as the young grow. The quills of young porcupines are soft at birth but harden within one hour.
Mothers remain with their young for up to six months.
During winter months, the animals seek refuge in caves, decaying logs, or hollow trees. They do not build nests. They often defend winter feeding trees from other animals. Porcupines do not hibernate, but they often remain in their dens during bad weather. During the summer, porcupines often climb trees to avoid pestering insects.