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Photograph by Joel Sartore
Tens of millions of bison once rumbled across the Great Plains on a quest for grazing. By the late 1800s nearly all had been slaughtered. Today most of the half million remaining bison are in captivity, like these on the Triple U ranch in South Dakota.
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Photograph by Joel Sartore
Millions of monarch butterflies travel to ancestral winter roosts in Mexico's shrinking mountain fir forests. Surfing winds from southern Canada and the northern U.S., they travel thousands of miles, taking directional cues from the sun.
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Photograph by Joel Sartore with Nathan Williamson
Pronghorn run fast—upwards of 60 miles an hour—but they rarely jump fences. Some ranchers plan to raise the lowest fence strands so pronghorn, like these near Medicine Hat, Alberta, can more easily slip under during their winter migration.
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Photograph by Joel Sartore
She’s given an insect to one of her nestlings, but now this black-capped vireo mother has two more hungry mouths to feed. In spring some 5,000 breeding pairs of the endangered bird leave western Mexico to build their nests in shin oak trees on the Fort Hood military base in Texas.
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Photograph by Joel Sartore
Worn like a backpack, a tiny plastic geolocator helps map bobolinks on their 12,000-mile flight from the grasslands and rice fields of Bolivia and Argentina to North America, including a stopover along the Platte River in Nebraska (above). If a male bobolink hears another male calling in his territory, he’ll chase the intruder away. So researchers who want to tag males with geolocators catch them by playing a recording of a male’s call, which to human ears sounds like the chirps of R2-D2, the robot of Star Wars fame.
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Photograph by Joel Sartore with Mitch Sternberg, Jennifer Lowry, and Naghma Malik, all U.S. Fish and Wildlife Service
A border wall along the lower Rio Grande in Texas divides nations as well as habitats, hindering essential daily movements of animals in the area. Bobcats would normally cross the border to find mates or catch dinner—this one caught a rat. The wall also blocks the daily rounds of ocelots, another member of the cat family.
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Photograph by Joel Sartore
Half a million sandhill cranes pause on the Platte River in Nebraska to fatten up on corn waste, worms, and other food in nearby fields. The break occurs on their spring flight from Mexico and the southern U.S. to breeding grounds in the far north.
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Photograph by Joel Sartore
Mountain goats in Montana’s Glacier National Park may travel thousands of feet a day—vertically. This one descended a sheer rock wall to lick salt and other exposed minerals. Nutrients that aren’t as available during the long winter may trigger the hankering.
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Photograph by Joel Sartore
Red-vested rattler wranglers with the Shortgrass Rattlesnake Association show off western diamondbacks they collected for the 45th annual Mangum Rattlesnake Derby in Mangum, Oklahoma. Thousands of people flock to the April event, where they can check out the snake pits and sample rattlesnake meat. Yes, it tastes like chicken. But, says Keith Kendall (center), it also “compares to frog legs. It’s got a good flavor to it.”
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Photograph by Joel Sartore
Out of hibernation—and hungry—many species of snakes follow the same scent trails year after year, no matter the obstacles. A western cottonmouth didn’t survive the trip across a levee road in Illinois.
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Photograph by Joel Sartore
Do dams impede the migration of bull trout in northern Montana? Genetic sampling allows technicians to ascertain a fish’s birth stream. Some fish are radio-tagged, moved above a dam, and tracked to find out if they return to their birthplaces to spawn. Kevin Duffy (above), a fisheries technician with Avista Utilities, monitors two fish in the Vermillion River that didn’t complete the journey to their natal streams. Duffy thinks they may have been thwarted by low water levels.
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Photograph by Joel Sartore
In the summer bull trout forge 50 miles upstream from Lake Koocanusa to spawn in the Wigwam River drainage in British Columbia. The cool, clear waters with loose gravel beds hold some 2,000 bull trout nests, among the highest concentration in the world.
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Photograph by Joel Sartore
Gas drilling projects, such as Jonah Field, impede pronghorn migration, and new homes restrict corridors to no more than a few hundred yards wide in places.
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Photograph by Joel Sartore with Cole Sartore
Mexican free-tailed bats spiral out of Eckert James River Bat Cave Preserve in Texas at dusk. The bats are hungry for pests like corn earworm moths—nutrition to keep milk flowing for their pups. Every spring millions of free-tails return to this cave.
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Photograph by Joel Sartore with Peter Coltman
Horse Hollow wind farm near Abilene, Texas, one of the world’s largest, has more than 400 turbines. The turbines’ spinning blades cause a drop in air pressure, which can kill bats.
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Photograph by Joel Sartore
These 32 bats and four songbirds represent an average yearly toll for each of the 23 turbines at a Pennsylvania wind farm. Raptors like the red-tailed hawk (top left) are rare victims.
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Photograph by Joel Sartore
Thousands of sandhill cranes roost on the Platte River during their annual migratory stopover at the Rowe Sanctuary near Gibbon, Nebraska. With water in the river fully appropriated for urban areas and agriculture, many wonder how long it will be until the Platte runs dry. Some 600,000 to 800,000 cranes use just a few miles of the river in central Nebraska—areas that have been mechanically cleared of the woody vegetation that the birds can’t tolerate.
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Photograph by Joel Sartore
Cowbirds are caught in a trap at Fort Hood near Killeen, Texas. The females will be killed and the males will be kept to lure other birds. The eradication of cowbirds has been going on for a while here in an effort to study the effect of their parasitism on endangered birds such as the black-capped vireo and the golden-cheeked warbler.
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Photograph by Joel Sartore
Caught in a mist net along Nebraska’s Platte River, a female bobolink will be tagged with a geolocator and released. When the bird is recaptured months from now, data from the geolocator will give researchers its migratory path.
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Photograph by Joel Sartore
The Spring Creek Prairie Audubon Center in Denton, Nebraska, is home to red-headed woodpeckers (above), among other birds and wildlife.
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Photograph by Joel Sartore
An interior least tern tends her nest at a mine along the Platte River near Fremont, Nebraska. The birds are listed as endangered in the U.S.; many mine companies halt work during the nesting seasons of rare birds. This area is slated to become a housing development in the next few years.
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Photograph by Joel Sartore
Monarch butterflies cover every inch of a tree in Sierra Chincua, Mexico. Millions of monarchs migrate here every year to spend the winter. The cool mountain climate slows their metabolism.
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Photograph by Joel Sartore
The Maxwell Game Preserve near Canton, Kansas, supports a herd of some 200 bison.
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Photograph by Joel Sartore
More than 40,000 people attended the 2010 Mangum Rattlesnake Derby in Mangum, Oklahoma. Among the attractions: a snake pit with several hundred western diamondback rattlesnakes.
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Photograph by Joel Sartore
Bison have room to roam at the Triple U Buffalo Ranch near Fort Pierre, South Dakota. The ranch's 2,000 head of bison go from pasture to pasture over 50,000 acres, traveling about 18 miles total every year.
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