Beech trees are often damaged only at their bases, perhaps because porkies have a hard time climbing this smooth-barked species. Although porcupines kill a few trees by girdling, most authorities agree the damage they cause over large areas is generally insignificant. In breeding season, porkies are especially vocal. Breeding takes place in September, October and into November, after a courtship often lasting several days. Courting porkies rub noses, chatter their teeth, walk on their hind feet or perform stylized, weaving body movements.
Males are polygamous and play no part in rearing young.
Unlike most rodents, porcupines are not prolific reproducers. Wildlife biologists have estimated that up to half of all adult females go unmated each year, and females that do become impregnated almost always produce just one offspring. The survival rate of young porcupines is high. After a gestation period of 205-217 days, the female gives birth in April, May or June. Birth may occur in a ground den, although the female doesn't generally select a particular site.