Michael Ellis has this Perspective on a mammal with one of the most effective defenses in the animal kingdom.
A friend asked me if porcupines live in the Bay Area. The short answer is yes. But they are very rare, plus they are mostly nocturnal. I have seen them a few times and only in New Mexico and Canada not here. Perched up in tree branches, they resemble stationary balls of thorns or even large bird nests so they are often overlooked.
For most of its existence, South America was an island continent disconnected from North America. But 2.8 million years ago, the Isthmus of Panama formed and connected North and South America. One of the greatest biogeographical events then took place — a massive exchange of mammals between the two continents. Camels, cats, bears, canids all flowed to South America. And north came some marsupials, primates and giant ground sloths. When the evolutionary dust settled South America ended up with jaguars and llamas and we got opossums and porcupines.
The porcupine (literally “spiny pig”) are not pigs but they are covered with spines. They’re the third heaviest rodent in the world. They range far north into Canada, way south to Mexico and all over the northeastern U.S. In California they are scattered throughout many regions, including the Bay Area, but are absent from the Central Valley, the Mojave and Coloradan deserts and southern coastal areas. While these vegetarians are well known for eating the bark of trees in the winter, during the warmer months almost any plant matter will suffice. Hence their wide distribution, but nowhere are they common.
These placid animals mostly have nothing to fear. Their first line of defense — quills— keep all but the most determined predators at bay. Cougars, bobcats, coyotes and especially fishers (a weasel relative) manage to take a few. But 30,000 heavily barbed quills and a very potent stench (described as rank human body odor) enable porcupines to plod along, only interested in finding the next thing to munch on. I would love to see another one, but only at a distance.