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PHOTOGRAPH BY CHRIS HOWES, WILD PLACES PHOTOGRAPHY, ALAMY STOCK PHOTO

PHOTOGRAPH BY KAR PHOTOGRAPHY, ALAMY STOCK PHOTO

The Pacific Northwest Trail is a wild wonder that takes hikers through one of America’s few inland temperate rainforests. For 1,200 miles, it winds along the Canadian border, through rugged mountains and gaping valleys in Montana, Idaho, and Washington, until it meets the Pacific Ocean. Since it was designated in 2009, the PNT has flown under the radar, compared to other popular long-distance trails, such as the Pacific Crest Trail and the Appalachian Trail. But the roughly 70-mile section of the PNT that runs through Montana’s Yaak Valley is a sore spot, at a time when outdoor spaces across the country have become popular due to the pandemic.
(The pandemic brought record crowds to America’s national parks.)
Conservationists and the Kootenai people say that the PNT threatens endangered grizzlies and Native traditions in the area. But to a handful of locals, the trail provides their only source of income.
The growing tussle among these groups sheds light on a bigger issue in the realm of conservation. In one of the wildest, most remote places in the contiguous United States, locals grapple with what defines public use, and who gets to decide the fate of a forest.

Protecting grizzlies

The brainchild of trail builder Ron Strickland, the PNT almost didn’t come to be. A 1980 U.S. Forest Service report dubbed the trail unnecessary, too expensive, and too dangerous. It concluded that the PNT posed a threat to both grizzlies and caribou (now extinct there). But Strickland was undeterred. He disputed the report’s findings and lobbied for decades to make his youthful hiking dream a reality.
Now, in-the-know trekkers (only about 75 a year by some estimates) take in “the mountains, the saltwater, the snowy peaks, the adventure, and the excitement,” that Strickland lauded.
But conservationists worry that soon more adventure-seekers will discover the trail, as the pandemic pushes people to wide, open outdoor spaces. Last summer, New York Times columnist Nicholas Kristof wrote an op-ed about the trail and broadcast his trek to millions of his social media followers. An adventure documentary about the trail called “Thru” (backed by outdoor gear companies, slated for release this year) is poised to add even more buzz.
Conservationists say the extra attention sets up a potential clash between hikers and grizzlies. “The Yaak’s alpine meadows are too small for people and bears to share them at the same time,” says writer and Yaak Valley Forest Council advocate Rick Bass, who’s been fighting to protect the valley he’s extolled in several books.
Grizzlies almost went extinct in the valley 40 years ago. In the years since, state and federal agencies have achieved a fragile recovery, bringing the bear population’s near single-digit numbers to about 60 in the broader region today. (Experts estimate roughly 30 travel the trail’s vicinity. The goal is to bring the total population in the valley to 100.)
(Bear safety rules are easy to learn. Why don’t people follow them?)
Area biologists have yet to document any cases of hiker-bear conflict on the PNT or a high volume of hikers pushing bears out of the region. But late last year, locals found the body of a female bear left in a driveway. Authorities suspect poachers, but the case is under investigation.
“I always start off this conversation by saying if it were up to me, I probably would not want to have a national trail going through grizzly bear habitat in the Yaak,” says the area’s program biologist, Wayne Kasworm. “The issue, though, is that’s not my choice. And since Congress has already designated that trail … the horse has already left the barn.”
Members of the Yaak Valley Forest Council hoped they could better manage foot traffic by suing the U.S. Forest Service over a years-overdue plan for the route as well as the formation of an advisory group of regional stakeholders. All of that fell apart and now, the plan is nine years overdue. Bass argues that it’s illegal to operate a trail without that backbone. Filed in 2019, the lawsuit is making its way through the courts.
“We want them to stop advertising the trail and its current location because no plan exists for it,” says Bass. “It’s out of compliance. It’s kind of like driving a car with an expired license.”
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PHOTOGRAPHS BY BRENDA LARISON

A blonde, or golden, plains zebra stands next to a normally colored animal at the Mount Kenya Wildlife Conservancy in July 2018.

Anyone can tell you that zebras have distinctive black and white stripes. But in some cases, these African equines sport unusual color patterns, such as large, black splotches or golden coats with light-colored stripes. Spotted zebras are appearing as well. In 2019 in Kenya’s Masai Mara National Reserve, scientists recorded a polka-dotted foal, with white spots covering its dark-brown body.
Such aberrations—often caused by genetic mutations that alter the production of melanin, a natural pigment—are generally rare among mammals. So biologist Brenda Larison found it striking that an unusually high number—an estimated 5 percent—of plains zebra living near Uganda’s Lake Mburo were abnormally striped.
Though plains zebras are the least threatened of the three species, their numbers have dropped by 25 percent since 2002, with around 500,000 animals ranging from Ethiopia to South Africa. Habitat fragmentation caused by fences, roads, and human development have squeezed zebra populations, like the one in Lake Mburu, into small pockets of land, preventing some of the animals from migrating between herds.
Migrating infuses populations with new genes, making it key to a species’ long-term survival. A lack of gene flow can lead to inbreeding and ultimately infertility, disease, and other genetic defects.
“The observation [of the oddly patterned zebras] led me to wonder: Is part of the reason that I’m seeing so many is because this population is inbred?” says Larison, who studies the evolution of zebra stripes at the University of California, Los Angeles. (Read more about Larison’s research in her own words.)
To find out, Larison and colleagues ran genetic analyses on 140 individual plains zebras—including seven animals with unusual coat patterns—from nine locations in Africa, including Nambia’s Etosha National Park and South Africa’s Kruger National Park.
Their study, published recently in the journal Molecular Ecology, found that smaller, more isolated populations of zebras had lower genetic diversity—not a surprise. But the study also revealed these isolated groups were more likely to produce abnormally striped zebras, suggesting these genetic mutations are caused by their poor genetic diversity.
While the study only looked at seven animals with odd patterns, the results could be a visual warning about the plains zebra’s future, says Larison.
“Even though plains zebras aren’t highly threatened, these genetic issues often show up before really problematic things start happening,” she says.

Genetic gaps

It’s possible odd stripes could make the zebras more obvious to predators; for instance, most recorded instances of polka-dotted zebras are as foals, not adults. Within their family groups, however, zebras don’t much seem to mind who’s striped and who’s spotted, notes Larison, whose latest research suggests zebra stripes help the animals avoid biting flies.
The more immediate concern, she says, is the plains zebra’s genetic health. For their analysis, Larison and her colleagues used advanced genetic sequencing techniques to closely study differences between not only inbred zebras, but also the zebra populations in distinct locations. (See pictures of a white giraffe and other unusually pale animals.)
“We found that there are populations that are possibly diverging more than they would under normal circumstances, because of human population pressure,” says Larison, whose work is supported by the National Geographic Society.
In other words, zebras are becoming genetically closer within their populations, but these populations are growing more distant genetically—mirroring their physical separation. This could eventually lead to new subspecies of plains zebra.

A conservation complication

That’s worrisome, says Desire Dalton, who studies wildlife genetics at the South African National Biodiversity Institute in Pretoria, because one of zebra conservationists’ main tools is translocation—moving individual members of one population to breed in another population.
If the populations are too genetically different from each other, though, the opposite of inbreeding can occur. Outbreeding, as it’s called, causes abnormalities from genes being too dissimilar.
There’s conflicting research on which plains zebra populations might be on their way to becoming genetically distinct, or subspecies. Scientists have not yet arrived at a consensus about how to define and group these subspecies.
But she agreed with Larison’s team that defining these groups is critical for managing the species. (Read how people are helping Grevy’s zebra, a rare species, survive drought.)
“You must be really sure what populations you can mix, and what you have to keep separate,” Dalton says.

Don't wait !

The new study is also a reminder to keep an eye on other African species that might not currently seem in dire straits, says Philip Muruthi, vice president for species conservation at the African Wildlife Foundation in Nairobi, Kenya.
For instance, Muruthi is concerned that the plains zebra could follow in the footsteps of another emblematic African species, the giraffe.
Due largely to habitat loss and poaching, giraffes have experienced a 30 percent population decline over the past 30 years; the International Union for Conservation of Nature now considers the animal vulnerable to extinction. Yet the phenomenon is still so little known it’s been dubbed a “silent extinction.”
That’s why the zebra study is crucial: By “highlighting the possibility that common species already have conservation issues,” Muruthi says, “it’s saying, Here is the issue. Don’t wait.”
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The brown tree snake (pictured at Omaha's Henry Doorly Zoo) can grow up to 10 feet long.
PHOTOGRAPH BY JOEL SARTORE, NATIONAL GEOGRAPHIC PHOTO ARK

Cargo ships likely introdueced the brown tree snake, which is native to other Pacific islands, to Guam in the late 1940s.
PHOTOGRAPH BY BJORN LARDNER, UNITED STATES GEOLOGICAL SURVEY

Snakes can sidewind over sand, leap between trees, and undulate underwater. Now, scientists have recorded an entirely new way of moving—forming a lasso-like loop to shimmy up a pole.
The brown tree snake, a tree-dwelling reptile native to Australia, Papua New Guinea, and several Pacific islands, was inadvertently brought to Guam after World War II, likely by cargo ships.The snakes spread rapidly, obliterating populations of local wildlife and driving 10 native bird species extinct. They have since inspired many attempts to control the invaders, from air-dropping drug-filled mice to snake-detecting dogs, but none have been successful.
In 2016, Colorado State University ecologists Julie Savidge and Tom Seibert had another idea: Installing eight-inch-wide metal cylinders—a type of baffle used to deter wildlife—at the base of bird nest boxes at the U.S. Geological Survey’s brown tree snake laboratory.
They suspected the nocturnal snakes couldn’t move up the smooth cylinders to prey on Micronesian starlings, a species that is not endangered but is dwindling on Guam. (Read more about invasive species’ impact on Guam.)
They were wrong. Video cameras placed near the experimental bird boxes revealed a snake roping its body around the pole, using this “lasso” to wiggle upward.
“We just kind of looked at each other in shock. I mean, this wasn't something a snake was supposed to be able to do,” says Seibert.
They’ve dubbed this newfound behavior “lasso locomotion” and detailed its mechanics in a paper published in January in Current Biology. It’s the fifth officially recognized type of snake movement, in addition to rectilinear, or moving in a straight line; lateral undulation, the classic snake slither; sidewinding, which is used to travel across sand; and concertina locomotion, the accordion-like climbing motion.
It’s “so unusual and wild,” says Sara Ruane, an evolutionary biologist at Rutgers University who not involved with the study. “I couldn’t get over it.”

Snakes on a pole

After witnessing the footage of the snakes lassoing themselves up the pipes in 2016, Savidge and Seibert called in Bruce Jayne, a biologist at the University of Cincinnati, to ask if he had ever seen anything like this in his 40-year career. “I was simultaneously flabbergasted and mystified,” says Jayne, a study co-author.
But because it was a choppy time-lapse video, Jayne needed to see clearly how the snakes were climbing the pole. Seibert returned to Guam in 2019 to set up a new experiment. He erected a steel duct pipe in a small pen, enclosed with five-foot-tall walls, and placed a dead mouse on top as bait. Then he released 15 wild-caught brown tree snakes into the pen. Five of the snakes climbed the pipe, which the researchers filmed in high definition. (See 22 spectacular pictures of snakes.)
In the footage, Jayne noticed a “gripping region” where the typically four-foot-long snake’s body crosses over itself as it’s climbing. When wriggling up trees, arboreal snakes usually need two gripping regions, which they achieve by wrapping their bodies twice around the trunk—a process called concertina locomotion.
But in the newly discovered lasso locomotion, the snake uses its one gripping region as an anchor, allowing it to wrap its body around only once, like a lasso. With this solid base, the snake then forms small bends in its body in wave-like motions, slowly propelling it upward.
But it isn’t easy for the snakes, which are always searching for food, Jayne says.
“Slipping was actually fairly common, so even though they can make upward progress,” he says, this is likely “a really hard thing for these snakes to do.”

"Still much to learn"

This form of locomotion has only been recorded in brown tree snakes climbing human-made poles in Guam, and so it’s not known whether it occurs in their native habitat or in other species, the authors caution.
But they surmise this unique movement—and ability to access prey in the treetops—is another addition to its already diverse repertoire, one that could help explain the snakes’ devastating impact on Guam’s ecosystems.
“There’s a whole suite of characteristics of this snake that have made it successful,” Savidge says, such as its wide-ranging diet and agility, which includes lunging through the air between tree branches. (Learn more about “flying snakes.”)
Savidge says this discovery led them to test a new ice cream cone-shaped baffle that seems to thwart the brown tree snakes from nest boxes. This design, which creates an angle that would make it more difficult for the snakes to climb, will be the subject of further research.
Ruane adds that even though brown tree snakes are heavily researched, their newfound locomotion would likely have gone unnoticed were it not for the video footage.
“It goes to show,” she says, “there's still so much to learn, even in well-known species.”
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