Threats to wildlife migration: Many animals are at risk of losing their ability to migrate due to shrinking habitat due to human development, industrial agriculture, and climate change.

One day in the fall of 1856, a family of gray squirrels living in rural New York emerged from their cozy nest in a chestnut tree, looked around, and joined half a billion other squirrels on a multistate walk. Ta. Waves of fur, claws, and sharp incisors swarmed like locusts in an army of squirrels 150 miles long, “devouring on their way everything that suited their taste,” said 19th-century naturalist John. Bachman writes.

Walls of squirrels pulsating across the landscape baffled naturalists and frustrated farmers, but these movements were a survival strategy, says University of Wyoming Haub, dean of the Haub School of Environment and Natural Resources and a longtime squirrel expert. says John Koprowski.

“Squirrels have a great sense of smell. They can often spot fruit-bearing or productive trees from miles away,” Koprowski says. “If you have a continuous forest where acorns and chestnuts are blooming and fruiting all at once and producing seed crops, that must be a pretty powerful smell wafting through the forest.”

The strategy worked. These rodent migrations caused squirrels to settle in new areas, find higher quality food, and create more squirrels. At one point, naturalist Ernest Thompson Seton estimated that the number of eastern gray squirrels could be in the billions.

This is almost unimaginable today. But this migration was not the only bizarre feat of wild animal dispersal. The now extinct Rocky Mountain grasshopper once moved across the country in waves. Passenger pigeons are also extinct, but they still migrated in flocks that darkened the sky. Jackrabbits are still abundant today, but they are more sedentary animals and once migrated in large numbers, devouring crops so heavily during the Dust Bowl that people forced them into enclosures and left them in their thousands. Killed.

Some species, especially birds and some large mammals such as deer and elk, still make pilgrimages. But many more squirrels, including the eastern gray squirrel, have lost the ability to migrate long distances due to a lack of large, connected forests, making their way through industrial parks, parking lots, six-lane interstates and subdivisions. I am no longer able to do that.

“There are millions of animals no longer there,” Koprowski said. “They’re giving us early warning that the way animals have evolved to use these spaces, they’re not functioning the way they have historically functioned.”

And the warnings are becoming even more dire. According to a 2024 United Nations report, 44 percent of the world’s migratory bird populations are in decline, largely due to a combination of habitat destruction from agriculture, unregulated residential and commercial development, pollution, and increasingly climate change. This is the result of overfishing.

But as the planet continues to change, as wild animals lose their freedom of movement, animals will need more of the ability to move from one place to another to find food or escape from threats. scholars say.

The amazing feats of immigration continue. These epic tours remind us that all is not lost.

Arctic rabbit running ultra

To the north of the Eastern Forest, once home to many eastern squirrels, lies another small mammal with a surprising penchant for long-distance exploration: the arctic hare.

The arctic hare is protected by special adaptations: a dazzling coat of thick fur that is white in winter and pale blue-gray or brownish in spring and summer to camouflage its surroundings, and it can withstand frigid temperatures. You can. But when the polar desert thermometer dips below -40 degrees Fahrenheit, they begin flying southwest, sometimes nearly 320 miles.

This marathon feat came as a surprise to scientists who discovered the journey in 2019.

Until now, researchers had largely believed that arctic hares were a sedentary species with little ability to disperse. Researchers at the University of Quebec at Rimouski knew that hares could travel as fast as 40 miles per hour, but they wanted to know how far they could travel.

Ludovic Landry-Ducharme, a doctoral student at the University of Quebec in Rimouski, who is continuing the research, was surprised to discover that the creatures regularly migrate hundreds of miles – perhaps even with more abundant plants. He said they were probably headed for warm meadows filled with glacier meltwater.

Canadian researchers published their findings in the journal Nature and found that climate change is likely to change as snow falls later and spring melts earlier, changing where and when important plants grow, and in what amounts. He emphasized that these patterns could be confounded by

The search for tasty food and escape from bad weather is one of the oldest adaptations in wild animals, best documented in more visible species such as mule deer in the American West, wildebeest in sub-Saharan Africa, and caribou in northern Canada. I am. Indigenous peoples have long known that wild animals migrate with the seasons, and many people followed their movements to take advantage of the weather and follow stable food sources.

But it’s only recently that researchers, equipped with the latest satellite technology, have begun to precisely map where wild animals move. These results made headlines with stories of mule deer that faithfully retraced the same 150-mile, even 250-mile migration across the mountain range.

Many animals, from arctic hares to mule deer, use what researchers call staging areas. These are areas along the way where animals can rest, breathe, and eat.

Wyoming migration researcher Hall Sawyer once described a stopover as a pit stop on a long interstate road trip. Drivers who stop for gas, coffee, or food make better decisions and arrive more rested than those who sprint away.

The same is true for animals. Their cross-border journeys may seem tortuous and precarious, but scientists say they are at risk and vulnerable to damage from highways and fences, droughts, fires and floods exacerbated by climate change. They say it’s increasingly threatened by everything from energy development to subdivisions and farmland.

Self-discovery in a year (or seven) of newts.

Anyone who has ever taken a walk through pockets of eastern forests has likely spotted the burnt orange eastern newt. The next time you see one, not only appreciate its ability to kill mosquitoes, but also wish it success in what amphibian researcher JJ Apodaca likens to rumspringa.

When newts enter left phase, fundamental physiological changes occur. Newts begin their lifelong journey in a pond, looking like olive salamanders with feathery gills and a slender tail, before crawling onto land, turning orange, and replacing their gills with lungs. Once on land, the newt sets off into the unknown, spending two to seven years meandering its tiny legs, sometimes miles, to what appears to be a faraway land. After roaming for years, they return to ponds or wetlands and dive into the water again to find a mate.

Those left walks are a critical time for young newts to search for the best food while growing and maturing. And the more fragmented their habitat is, the less cover they will find on the leafy forest floor and the more likely they are to come into contact with car tires.

They aren’t the only amphibians that need space to roam. Green salamanders do not fly horizontally, but instead look upwards in search of greener pastures. Salamanders climb trees in search of better food (and may also avoid becoming food).

But as humans continue to cut down some trees and pests and diseases target others, fewer and fewer salamanders survive.

The ability to search for new territory is not only important for the species’ population as a whole, but will become even more important as habitat shrinks and the climate changes.

In March 2018, a female arctic fox wearing a tracking collar paddled more than 4,700 miles from start to finish to Ellesmere Island in Canada from a research site in the Norwegian Islands to Ellesmere Island in Canada in just four months. And she’s certainly not alone. Arctic foxes build bridges across continents, cross ice sheets, connect with distant populations, and maintain robust genetics across generations, according to research by Eva Fuglei, a researcher at the Norwegian Polar Institute. It is said that he has the ability.

But when the sea ice melts, these people are likely to become stranded.

animal island problem

Eastern gray squirrels continued to encamp regularly until the 1960s, when naturalists reported some of the last large-scale encampments, but their numbers declined over the years. The long migration finally came to an end, as the human desire for timber and space for parking and shopping centers eventually proved too much for even the most industrious of squirrels.

Today, relative populations of eastern grays are much smaller, living in fragmented habitats on islands confined by roads and development.

Wildlife, whether small animals like salamanders or large animals like wildebeest, do not do as well on islands as on landlocked sites. A paper published in Nature in 1987 showed that more species in 14 national parks in the American West went extinct than were naturally re-established. What’s called the island effect shows that even if animals live in protected areas like national parks, those parks are often too small.

“The impact that habitat loss and fragmentation has on populations, from intact to fragmented, is as close as you can get to the golden rule of conservation,” said Wyoming Cooperative Fish and Wildlife Research Unit leader and longtime resident. says researcher Matthew Kaufman. “When you move from a large, intact habitat to a place where the same habitat is fragmented but the animals can’t move, the robustness of the population decreases.”

Fortunately, recent years have seen promising moves to reconnect habitats even in increasingly fragmented landscapes.

Wildlife Crossing is a collaboration between states, nonprofits, and the federal government across the country to provide safe passage for everything from salamanders to mountain lions from the forests of Massachusetts to the multi-lane highways of Southern California. We have been working on installing sidewalks.

Apodaca’s organization, Amphibian and Reptile Conservancy, recently completed work on a culvert under the highway to guide increasingly endangered pond turtles from one side to the other. , giving them access to diverse habitats they would otherwise risk waddling down roads to seek out.

States like Wyoming and Colorado are using maps of deer, elk and pronghorn movements to fine-tune and even change zoning locations for oil and gas development. Wildlife managers also understand the importance of long-distance pit stops to wildlife abundance.

Conservationists also praise efforts like President Joe Biden’s plan to conserve 30 percent of the nation’s land, freshwater and oceans by 2030 as a way to preserve critical habitat and migration corridors. did. However, the future of these efforts under the incoming Trump administration remains uncertain.

Eastern North America may never again see flocks of 500 million squirrels flying through forests in search of rich acorns, but researchers say it’s not too late for other species.