On an autumn day in 1856, a family of gray squirrels in rural New York emerged from a cozy nest in a chestnut tree, looked around, and joined half a billion other squirrels in a multi-state walkout. Waves of fur, claws and sharp incisors swarm like the locusts of an army of squirrels that can be up to 150 miles long, “devouring in their path whatever suits their taste.” Written by John Bachman, a 19m– Naturalist of the Century.
John Koprowski, dean of the University of Wyoming’s Hub School of Environment and Natural Resources and a longtime squirrel expert, said the walls of Sciurus carolinensis across the landscape confused naturalists and frustrated farmers, but the movements were a survival strategy.
“Squirrels have an amazing sense of smell. They can often find fruiting trees, trees with good crops, from miles away,” Koprowski said. If it does, then it can be a pretty strong smell through the forest.”
The strategy worked. By undertaking these mass rodent odysseys, squirrels settled in new territories, found high-quality munchies, and, in turn, produced more squirrels. At one point, naturalist Ernest Thompson Seton estimated that eastern gray squirrels numbered in the billions.
It is almost impossible to imagine today. But this migration was not the only strange feat of dispersal by wild animals. D The now extinct Rocky Mountain Locust At one time the wave went across the country. Passenger pigeons, also extinct, migrate in flocks so dense that they darken the sky. Jackrabbits — still abundant today but more persistent — once migrated in droves, tearing through crops so viciously during the Dust Bowl that people herded them into pens and killed them by the thousands.
Some species, especially birds and some large mammals like deer and elk, still make the pilgrimage. But many others, including the eastern gray squirrel, have lost the ability to travel long distances, lack large contiguous forests and are unable to move through industrial parks and parking lots on six-lane interstates or subdivisions.
“We don’t have millions of animals in those places anymore,” Koprowski said. “They’re giving us an early warning that they’re not working the way they have historically, the way animals have evolved to use these spaces.”
And that warning is getting more dire. A 2024 UN report It found that 44 percent of the world’s migratory species are declining, as a result of overhunting along with habitat destruction due to agriculture, sprawling housing and commercial development, pollution and increasing climate change.
Yet as wildlife loses freedom of movement, biologists say the ability to move from one place to another to find food or escape threats will become more essential as our planet continues to change.
Some incredible feats of immigration still hang. These epic journeys serve as a reminder that all is not lost.
Arctic hares that run ultras
North of the once-abundant eastern forests, with their once-abundant eastern squirrels, there is another small mammal with surprising interest in long-distance exploration: the arctic hare.
Protected by a special adaptation—a glossy coat of thick fur that turns white in winter and thins and turns blue-gray or brown in spring and summer to blend in with its surroundings—the arctic hare can survive freezing temperatures. But when the thermometer drops below negative 40 degrees Fahrenheit in polar deserts, They started jumping to the southwest – Sometimes for about 200 miles.
This marathon feat was a surprise Scientists who invented travel In 2019.
Previously, researchers mainly believed arctic hares “Sedentary species with low dispersal ability.” Researchers at the University of Quebec in Rimouski knew rabbits could travel fast — up to 40 miles per hour — but they wanted to see how far they could go.
They were shocked to discover that the animals regularly traveled hundreds of miles — perhaps headed for warmer pastures with more abundant vegetation and glacial meltwater, said Ludovic Landry-Ducharme, a PhD student at the University of Quebec in Rimouski, who is leading the research.
D Canadian researchers published Their work in journals the nature And underscored that climate change could well disrupt these patterns as snow comes later and spring melt begins, changing where and when — and how abundantly — important plants grow.
The tendency to seek good food and survive poor weather conditions is one of the oldest adaptations in wildlife and is often documented in more visible species such as mule deer in the American West, wildebeest in sub-Saharan Africa, and caribou in northern Canada. Aboriginal people have long known that wildlife migrates with the seasons and many follow those movements by taking advantage of the weather and following with consistent sources of food.
But it was only recently that researchers with modern satellite technology began to map exactly where wildlife had migrated. headlined the story of that result Mule deer faithfully follow the same 150- or even 250-mile migration. Up and over the mountains.
Many animals — from Arctic hares to mule deer — use what researchers call stopover points. These are areas along the way where species can rest, breathe and eat.
Wyoming migration researcher Hall Sawyer once described the stopover Pit stops on long interstate road trips. Drivers who stop for gas, a cup of coffee and food make better decisions and arrive better rested than those who power through.
For animals, it is no different. Their cross-country trips may appear erratic and erratic, but according to scientists, they are critical and increasingly threatened by everything from highways and fences to drought, fires and floods to energy development, subdivisions and agriculture worsened by climate change.
A newt’s year (or seven) of self-discovery
Anyone who has walked through pockets of eastern forest has likely seen a burnt-orange eastern newt. The next time you see one, wish it well not only thanks to its mosquito-killing abilities but also for what amphibian researcher JJ Apodaca has compared to Ramspringa.
When a newt enters its eft stage, it undergoes a fundamental physiological change. The newt begins its life as an olive salamander with feathery gills and a slender tail before it crawls on the ground, turns orange and swaps its gills for a set of lungs. Once on land, the newt sets off for parts unknown, wandering for two to seven years—sometimes for miles—on its tiny legs that it surely considers distant lands. After years of wandering, it returns to a pond or swamp, dives back into the water, and searches for a mate.
These eft walks are an important time to find the best food while juvenile newts are growing and maturing. And the more fragmented their habitat, the less cover they can find on leafy, forested floors and the more likely they are to be run over by car tires.
They’re not the only amphibians that need room to roam. Instead of scuttling horizontally, green salamanders look upward for greener pastures. Salamanders climb trees for good food (and possibly avoid food).
But as humans continue to cut down some trees — and pests and diseases target other trees — fewer and fewer salamanders remain.
The ability to find new territories is not only important for a species’ overall population, but will become even more important as habitat shrinks and climate changes.
In March 2018, a female arctic fox wearing a tracking collar traveled from a research site in the Norwegian archipelago to Canadian Ellesmere Island, paddling more than 2,700 miles from start to finish in just four months. And he’s certainly not the only one. According to a study by Norwegian Polar Institute researcher Eva Fugli, arctic foxes have the ability to bridge continents, cross ice sheets and connect with distant populations – keeping their genetics strong for generations.
But as the sea ice melts, that population will likely become isolated.
The problem with Animal Island
Eastern gray squirrels continued their periodic encampments more or less every year, until naturalists reported the last large ones in the 1960s. Human desire for wood and space for parking lots and shopping centers eventually proved too much for even the most industrious squirrel, and the long migration finally ended.
Today, a relatively small population of Eastern Grays live on islands blocked by fragmented habitats, roads or development.
Wildlife, even as small as salamanders or as large as wild boars, do not function on islands as they do in connected landscapes. A 1987 paper published in the journal the nature showed that more species 14 extinct in the west American national parks were naturally re-established there. The island effect, it’s called, shows that even if animals live in protected areas like national parks, those parks are often too small.
“The effects of habitat loss and fragmentation on populations, from intact to fragmented, is close to our golden rule in conservation,” says Matthew Kaufman, leader of the Wyoming Cooperative Fish and Wildlife Research Unit and a longtime migration researcher. “When you go from a large, intact habitat to the same habitat but fragmented, where animals can’t move, the population will be less robust.”
Fortunately, in recent years, there have been promising steps to reconnect habitat, even in an increasingly fragmented landscape.
Across the country, states, nonprofit organizations and the federal government have worked together to install wildlife crossings — over- and underpasses — that provide safe passage for everything from salamanders from mountain lion from Massachusetts forest from Multi-lane interstates in Southern California.
Apodaca’s organization, the Amphibian and Reptile Conservancy, recently completed a culvert under a highway to transport increasingly endangered bog turtles from one side to the other. Grant access to organisms For diverse habitats it would otherwise wander dangerously across the road.
States like Wyoming and Colorado are using maps of deer, elk and pronghorn migration to change oil and gas development locations or potentially even revise subdivisions. Wildlife managers also now understand the importance of those long-distance burrows to wildlife abundance.
Efforts like President Biden’s plan to conserve 30 percent of the nation’s land, freshwater and oceans by 2030 have been praised by conservationists as a way to maintain critical habitat and migration routes. The future of that effort under the incoming Trump administration, however, remains bleak.
Eastern North America may never again see herds of half a billion squirrels swarming through forests for green crops, but for other species, researchers say, it’s not too late.
