How do female porcupines give birth? Don’t they get poked by their baby’s quills?

Answered by Dr. Quinn Shurtliff, Biologist, INL ESER Program
The short answer to the first question – very carefully.

It’s true – baby porcupines, called porcupettes, are born covered with quills. Those quills, however, are soft, moist, and flexible, and it takes about an hour for them to dry out and become prickly. What’s more, the newborn enters the world entirely enclosed by a thin placental sac that tears open immediately after the baby makes its entrance. Some naturalists think this sac may make the birthing process a bit easier.
In my mind, it’s not the quills but the size of the baby that would be uncomfortable for mom. Porcupines generally have only one baby per year, which at birth weighs about one pound. Adult females weigh about 15 lbs, so relatively speaking, that would be like a 140 lb. woman giving birth to a 9 lb baby.

You may wonder why porcupines have only one large offspring when most rodents (yes, the porcupine is the 3rd largest rodent in the world, behind the beaver and capybara) spread out their reproductive effort by having several small babies in one or more litters each year. Evolutionary theory suggests there are two main strategies for reproduction. If your babies are very likely to get eaten, it would be best to produce many small rather than one large offspring in hopes that at least one will survive and reproduce. If your babies are relatively less likely to be eaten before they grow up, you’re better off putting a lot of energy into few, well-developed offspring. Being large and well-developed at birth improves one’s chance of survival.

What would you guess is the predation pressure on young porcupines compared to other rodents?

Quills

The North American porcupine has about 30,000 quills. Although porcupines can’t shoot their quills like arrows, the slightest touch can lodge dozens of quills in the predator’s body.

Quills are modified hairs made from keratin, which is the same material that your hair and fingernails are made from. They are like tiny needles with sharp tips and barbs on the sides. The sharp tips of the barbs allow them to pierce a predator’s skin easily, but the barbs on the sides of the quill make them difficult to remove. Each quill has up to 800 barbs.

Materials: pencil, cardboard, tissue paper, scissors

1. Draw a long, skinny triangle on the cardboard and cut it out.
2. Draw a long, skinny triangle with barbs at the tip, as shown at the right. Cut it out.
3. Poke the barbless triangle about halfway through the tissue paper. Repeat with the barbed triangle. Which was easier to push through the paper?
4. Gently pull the barbless triangle out of the tissue paper. Repeat with the barbed triangle. Which was easier to remove?