One sunny June morning, a walk into the sagebrush of western Wyoming revealed a startling sight: two pronghorn fawns, nearly underfoot, sprang up and vanished across the vast landscape with astonishing speed. These spindly-legged creatures, embodying the essence of the wild West, are among the fastest land animals on Earth, capable of bursts up to 60 miles per hour, significantly outrunning horses and wolves. Their specialized anatomy—long legs, oversized hearts and lungs—makes them perfectly adapted to the open sagebrush basins of Wyoming, where they have thrived for tens of thousands of years, subsisting on shrubs and evading predators. However, the modern pronghorn faces challenges far beyond the natural, including habitat fragmentation from rural housing and energy development, and the relentless march of climate change, which is steadily warming the very environment in which they evolved.

The world that the pronghorn, and the author, inhabit is undergoing profound transformation. More frequent and intense droughts, milder winters with less snow, and earlier spring melts are leading to lower summer stream flows. The region experiences fewer frost days, hotter summers, and more violent storms. These climatic shifts are drying out conifer forests, making them susceptible to devastating wildfires, while invasive, fire-adapted grasses are encroaching on rangelands. In 2024 alone, Wyoming witnessed over 1,300 square miles consumed by fire, more than double the area affected in recent significant fire years. The impact on wildlife, including the pronghorn, is starkly evident.

In the expansive Powder River Basin of northeast Wyoming, a region characterized by rolling grasslands and shrub-covered bluffs, a wildfire in August 2024, fueled by high winds, rapidly escalated into an inferno that blackened hundreds of square miles within a single day. When evacuation orders were lifted, ranchers returned to find familiar landscapes scorched and unrecognizable. As the charred earth cooled, wildlife managers and landowners discovered the tragic toll: at least 70 pronghorn, North America’s fastest land animal, had perished, some succumbing near fences, others caught in the open by the relentless flames.

The author’s thoughts turned to the future, particularly the world her children will inherit. Arriving home from the hospital under skies stained with wildfire smoke in September 2018, she acknowledges the uncertainty of the coming decades but recognizes that the landscape will be irrevocably altered. Her children will grow up in an era vastly different from the one generations have known.

This is not the first climatic upheaval the pronghorn lineage has weathered; their ancient ancestors emerged in the fossil record during the Miocene epoch, approximately 20 million years ago, a period warmer than the present. The modern pronghorn evolved later, during the ice ages, and demonstrated remarkable resilience when the planet warmed dramatically around 12,000 years ago, an event that led to the extinction of most large North American mammals. The pronghorn, however, endured and adapted.

Researchers now discuss "state shifts," where entire ecological systems, such as pine forests or sagebrush steppes, can transform into entirely new types of environments due to climate change. The critical question arises: will pronghorn navigate this new era of climate-driven transformation as successfully as they did 12,000 years ago, and what does this portend for humanity? Perhaps by understanding the survival strategies of the pronghorn’s ancient ancestors, we can glean insights into how their descendants, and indeed our own species, can adapt to an increasingly unpredictable future.

The sight of pronghorn grazing near the edge of town in southeast Wyoming during spring snowstorms, migrating from winter grounds to summer fawning areas, evokes a sense of deep time. With their distinctive large eyes and uniquely shaped horns, pronghorn appear almost otherworldly, yet they are living relics of a time when North America was populated by a diverse array of now-extinct megafauna. To understand their resilience, one must delve into the ancient climates, plant life, and animal communities of the past.

Within the University of Wyoming Geological Museum, a striking mural depicts the Laramie Valley during the Pleistocene epoch, a period marked by ice ages spanning from 2.58 million to 11,700 years ago. The artwork portrays a scene with a saber-toothed cat confronting a massive bison, while mammoths stand warily in the background. The landscape is characterized by scrubby tundra, willows lining a river, and glaciers descending from the treeless Medicine Bow Mountains, their peaks cloaked in deep snow and ice.

Bryan Shuman, a paleoclimatologist at the University of Wyoming, studies the geological records of past environments. His research, based on microscopic particles in lake sediment cores and the mapping of ancient shorelines, reconstructs the hydrology, climates, and ecologies of past eras. Shuman’s work indicates that Pleistocene Laramie was significantly colder than today, with average year-round temperatures during the coldest periods plummeting by as much as 18 degrees Fahrenheit. This intense cold fostered permafrost, leaving behind distinctive polygon-shaped ground patterns still visible today.

The mural’s depiction of extensive glaciers and sparse plant cover aligns with Shuman’s findings, supported by clear geomorphic evidence of glacial extent. During these frigid periods, the landscape was dominated by grasses and sagebrush, with some pollen suggesting the presence of low, shrubby willows, similar to those found in the modern Arctic. The region was also considerably drier than it is now; Shuman notes that the current period is likely the wettest in at least the last 20,000 years for this region. Furthermore, the late Pleistocene was characterized by intense winds and widespread dust, as glaciers pulverized rocks into fine silt that was then carried by the wind across vast distances, shaping dunes and depositing layers of glacial dust throughout the Midwest. Picturing pronghorn navigating such a harsh, cold, dry, windy, and dusty ancient landscape presents a stark contrast to their modern habitat.

The Pleistocene pronghorn faced formidable predators, including the American cheetah (Miracinonyx), a long-legged feline adapted for pursuit, the formidable American lion, one of the largest cat species to have ever existed, and the powerful Beringian wolf with its robust jaws. Fossil evidence from Natural Trap Cave, a unique geological formation in northern Wyoming, provides a preserved snapshot of these interactions. This bell-shaped cavern, with an opening about 15 feet across, has served as a natural trap for tens of thousands of years, with animals falling over 80 feet to their deaths. The cave’s stable 42-degree Fahrenheit temperature has preserved an extraordinary collection of complete skeletons, offering invaluable insights into the fauna of the past.

Julie Meachen, a vertebrate paleontologist, has led research at Natural Trap Cave since 2014. Her initial descent into the cavern revealed a treasure trove of fossils, including remains of camels, cheetahs, horses, and mammoths, alongside evidence of Pleistocene lions, wolves, and bears. In the 1970s and 80s, researchers had already unearthed pronghorn fossils dating between 17,000 and 20,000 years ago, morphologically indistinguishable from modern specimens. The cave also yielded remains of modern bighorn sheep, coyotes, extinct stilt-legged horses, musk oxen, camels, and giant short-faced bears. Recent excavations by Meachen’s team have uncovered mammoth bones, indicating the presence of at least three individuals that met their end in the cave during the Pleistocene.

Todd Surovell, an archaeologist specializing in hunter-gatherers and late-Pleistocene extinctions, highlights the abundance of Columbian mammoths, the largest mammoth species in the Americas, which ranged from Canada to Mexico. He describes finding "tons of mammoths" in Wyoming. Imagining these massive creatures alongside pronghorn, evading predators like lions and bears, paints a vivid picture of a lost world, a world that ultimately saw the demise of most of its large inhabitants.

On a geological timescale, the 7,000-year transition from the last ice age to the Holocene epoch, which we inhabit today, occurred rapidly. However, for the pronghorn, these changes unfolded over many generations. Around 17,000 years ago, shifts in Earth’s axial tilt led to increased solar radiation, initiating the melting of ice caps. As reflective ice receded, darker ground surfaces absorbed more heat, amplifying warming. This process, coupled with the massive influx of freshwater into the oceans, altered ocean currents, leading to the release of carbon dioxide. This elevated CO2 acted as a greenhouse gas, trapping heat and accelerating global warming.

The warming trend, driven by a complex interplay of orbital changes, ice sheet dynamics, dust cycles, and oceanographic shifts, caused atmospheric carbon dioxide levels to rise significantly. By approximately 10,000 years ago, a more than 40% increase in CO2 had warmed the planet by 7 to 11 degrees Fahrenheit. This warming trend led to increased precipitation in central North America, transforming arid grasslands into more verdant environments and allowing forests to expand northward. While beneficial for trees and some species, these changes proved catastrophic for many large mammals.

The end of the Pleistocene marked a period of profound biodiversity loss. Of the numerous large mammals that once roamed North America, an estimated 59 species, and potentially more, vanished, leaving only 26 extant today. One analysis suggests that 72% of large mammal species disappeared from the continent, including horses, mammoths, giant beavers, ground sloths, and many predators. The general trend observed is that larger animals faced a higher extinction risk. This mass extinction event, occurring within a relatively short geological span of about 13,800 to 11,400 years ago, remains a subject of intense scientific debate, with potential contributing factors including human influence, asteroid impacts, or novel diseases, though abrupt climate change is widely accepted as a primary driver of this biodiversity crisis.

Among the survivors of this dramatic planetary transition stands the pronghorn antelope. Antilocaprids have a lineage on the continent that predates that of deer, elk, and caribou by more than four times, and that of bison and bighorn sheep by a considerable margin. The modern pronghorn, the sole living descendant of the first antilocaprids, is unique to North America, having evolved to thrive in its diverse ecosystems.

Christine Janis, a professor emerita of ecology and evolutionary biology, emphasizes the pronghorn’s remarkable survival capabilities. Their ancestors navigated earlier extinction events involving ancient deer-like animals, and the modern pronghorn lineage persisted through the Pleistocene extinctions alongside horses and camels, until its contemporaries largely disappeared. The exact mechanisms of their survival remain a subject of study, but several theories have emerged. Meachen points to their ability to thrive with limited water and to subsist on dry, scrubby vegetation that other large herbivores could not process, affording them a significant advantage in arid environments. Surovell suggests that the extinction of the American cheetah, a primary predator, may have also played a role in their continued success.

Janis highlights the pronghorn’s high-crowned teeth, which allow them to efficiently consume low-growing, gritty browse, with ample crown height to accommodate wear from a lifetime of chewing dusty Pleistocene plants. She also notes their small size and rapid reproductive rate, typically producing two fawns annually, a stark contrast to the infrequent offspring of larger mammals like camels or mammoths. Janis encapsulates the pronghorn’s survival strategy with a succinct lesson: "Be small and be adaptable in your diet. That’s a good way to survive."

Pronghorn have demonstrated an extraordinary capacity for adaptation, and the challenges they face are far from over. Global surface temperatures continue to break records annually, and the rate of warming driven by anthropogenic greenhouse gas emissions is projected to far exceed the pace of the 7,000-year transition that ended the ice ages. This rapid warming, occurring at a speed potentially unprecedented since the asteroid impact that wiped out the dinosaurs 66 million years ago, raises critical questions about the adaptability of our own living systems.

For the author, a resident of Wyoming and mother of two, contemplating this future is a profound challenge. Yet, studying the pronghorn’s resilience has offered a shift in perspective. While acknowledging the hardships of the deep ice ages, she recognizes the benefits of increased precipitation in modern times, which has fostered the growth of forests and supported species like the pronghorn. The Earth’s history, spanning billions of years and myriad climates, from subtropical Wyoming to glacial epochs, underscores the dynamic nature of the planet and the continuous adjustment of living systems. The author notes that her children, unlike many animals, possess the capacity to alter their diets and adapt to diverse climates and environments, even migrating to new habitats if necessary.

When a wildfire swept through Wyoming’s Powder River Basin in 2024, consuming nearly 275 square miles, the 70 pronghorn that perished were part of a much larger population, with tens of thousands of survivors in the area. These survivors, in turn, birthed new fawns and thrived on the fresh green grass that emerged in the burned areas the following spring.

Perhaps the enduring lesson from the pronghorn is not to dwell on the past or anxiously anticipate the unknown future, but to engage with the present moment with attentiveness and care. Observing the subtle shifts in wind patterns and the scents carried on the air, understanding their home habitats deeply, and aligning personal behaviors with the forces of nature are crucial. The pronghorn’s resilience speaks to the importance of recognizing environmental changes, such as the way snow drifts, the types of plants that emerge after a rain, and the unique characteristics of each passing spring. It is a call to teach children to observe the natural world, learn the rhythms of animal migrations, breathe deeply, and continue moving forward with a grounded connection to the Earth.