Above photo courtesy RedButteCanyon.net. Porcupines tend to eat bark for sustenance.
History of The Disappearance of Porcupines:
Humans did not always see porcupines as a nuisance. Native Americans have long regarded the animal with respect and even admiration. The large rodent was viewed as a minor animal spirit, usually representing self-defense and caution. Some tribes also associated porcupines with humility, modesty, and good luck. The animals supplied food when other game was scarce, and their stiff quills were softened, dyed, and woven into leather shirts, medicine bags, and moccasins.
Early settlers also held a magnanimous view toward porcupines. Trappers and woodsmen never killed them without cause, because the slow-moving, easy-to-approach rodents could be an emergency food source to someone lost in the wilderness. Settlers believed, as did Indians, that killing a porcupine was bad luck.
Attitudes began to change in the 1930s as porcupines consumed young trees planted by the fledging U.S. Forest Service to replace those logged or lost to wildfire. Soon the rodents were depicted as a scourge of America’s national forests. A 1936 Forest Service press release in the Spokesman-Review called porcupines a “new major menace to livestock and timber in Montana’s national forests.” So abundant were porcupines, the agency claimed, “that they are causing almost as much loss to timber as fires.” In 1955, zoologist and ranger-naturalist R.R. Lechleitner wrote in Mammals of Glacier National Park, “Porcupines are quite abundant…and appear to be more numerous in the higher regions.” He related a story of counting two dozen porcupines in a single evening while driving roughly 24 miles along the Going-to-the-Sun Road from the Loop to Sun Point.
By the 1950s, porcupine eradication programs were in full swing on national forests and private timber lands throughout the United States. Strychnine-laced salt blocks were used to control porcupine numbers in some national forests until 1972, when the use of toxicants on federal lands was banned.
Though federal poisoning killed many porcupines, John Vore, Montana Fish, Wildlife & Parks Game Management Bureau chief and previously the department’s wildlife biologist in Kalispell, doesn’t believe it explains why the animals are so scarce today. He points out that porcupines were common into the 1980s, years after the most intensive eradication programs ended. What’s more, adds Glacier National Park wildlife biologist John Waller, no poisoning took place in the park, yet porcupines are now rare there, too. “It’s a notable occurrence when you see one,” Waller says.
Could fishers and mountain lions, which purposely hunt porcupines, be to blame? Probably not, says Vore. Even though Montana’s mountain lion population has increased since the 1980s, the predators don’t prey on enough porcupines to account for the massive declines. Fisher numbers also have grown, and these large members of the weasel family are able to kill any porcupine they find by biting the rodent’s snout, flipping it over, and attacking its vulnerable belly. Yet fisher populations have low densities, so “even when numbers are up, there are never a lot of fishers around,” Vore says.
Another possibility is climate change. “Fire frequency and severity and mountain pine beetle epidemics have impacted thousands upon thousands of acres of habitat and the trees that porcupines need,” says Chris Hammond, FWP nongame wildlife biologist in Kalispell.
One factor no one can rule out is the possibility of an unknown epidemic afflicting porcupines. Says Vore, “There may be a porcupine or rodent-specific disease out there that we just don’t know about.”
Hoping to start finding some answers, in 2006 Foresman enlisted a graduate student, Katie Mally, to study the differences between high-elevation porcupines, which seemed increasingly rare, and low-elevation porcupines, still common in western Montana. Mally surveyed wildlife biologists, foresters, landowners, and others to learn of any sightings since 1996. Of the 183 instances where people reported seeing porcupines in the previous decade, not a single one was at an elevation above 4,000 feet.
Undaunted, Mally spent the next summer scouring western Montana mountains looking for porcupine sign. Her search came up empty. “If she had located some porcupines, she could have radio-collared them and found out what habitats they used, what they ate, reproductive success, causes of death, that sort of thing, in order to start getting at what might be behind the declines,” says Foresman.
With no high-elevation porcupines to study, Mally instead began documenting porcupine habitat in the lower Bitterroot Valley. After a year of study, Mally found that porcupines were most common in areas with low-elevation wetlands containing hawthorn and cottonwoods. “That was important baseline information, but unfortunately we’re no closer to understanding what happened to the high-elevation porcupines,” says Foresman.
Foresman suspects that a wide range of factors are at play. “The biggest of all could be the fact that porcupines produce just one baby each year,” he says. “When a female rabbit dies, she probably has produced 10 or 12 babies. But when a female porcupine is killed—by disease, predators, or shooters—she might have only produced one or two young in her lifetime,” he says. “It doesn’t take much to knock down such a slow-growing population and keep it from recovering.”
Foresman notes that porcupines are still commonly killed by tree nursery owners concerned about their stock and bird hunters hoping to prevent their dogs from getting quilled. Porcupines are classified as an unprotected nongame species that can be shot on sight. “What concerns me most are the porcupines shot just because they are there, for so-called ‘sport,’” Foresman says. That indiscriminate mortality, coupled with things scientists still don’t understand, like habitat change and disease, could be enough to keep porcupines from ever recovering enough to once again become a common species that people encounter while exploring western Montana’s forests. 
Gary Strader, an employee of the U.S. Department of Agriculture, claims that his employer, a branch of the federal Department of Agriculture called Wildlife Services, has long specialized in killing animals that are deemed a threat to agriculture, the public and – more recently – the environment.
Since 2000, its employees have killed nearly a million coyotes, mostly in the West. They have destroyed millions of birds, from nonnative starlings to migratory shorebirds, along with a colorful menagerie of more than 300 other species, including black bears, beavers, porcupines, river otters, mountain lions and wolves.
And in most cases, they have officially revealed little or no detail about where the creatures were killed, or why. But a Bee investigation has found the agency’s practices to be indiscriminate, at odds with science, inhumane and sometimes illegal.
With steel traps, wire snares and poison, agency employees have accidentally killed more than 50,000 animals since 2000 that were not problems, including federally protected golden and bald eagles; more than 1,100 dogs, including family pets; and several species considered rare or imperiled by wildlife biologists.
Since 1987, at least 18 employees and several members of the public have been exposed to cyanide when they triggered spring-loaded cartridges laced with poison meant to kill coyotes. They survived – but 10 people have died and many others have been injured in crashes during agency aerial gunning operations since 1979.
A growing body of science has found the agency’s war against predators, waged to protect livestock and big game, is altering ecosystems in ways that diminish biodiversity, degrade habitat and invite disease.
Sometimes wild animals must be destroyed – from bears that ransack mountain cabins to geese swirling over an airport runway. But because lethal control stirs strong emotions, Wildlife Services prefers to operate in the shadows. 
: Montana Outdoors, “Where Have All The Porcupines Gone?” bhttp://fwp.mt.gov/mtoutdoors/HTML/articles/2015/porcupines.htm#.Wc6D1BNSxBw:
: The Sacramento Bee, “The killing agency: Wildlife Services’ brutal methods leave a trail of animal death” by Tom Knudson: www.sacbee.com/news/investigations/wildlife-investigation/article2574599.html