What an 'Elephant Graveyard' Teaches Us About Climate Change

A prehistoric Florida fossil site provides an unprecedented look at gomphotheres—elephant relatives that lived in a warming climate—and offers insights for today

• By Stephenie Livingston
• Conservation
• Jun 27, 2024

Gomphotheres—a group of animals including the Rhynchotherium (illustrated above, by Pedro Toledo/CC BY)—existed for 20 million years, but only three of their cousins made it to the 21st century. Among those is the Asian elephant (background detail photo above, by Karine Aigner), listed as endangered by the International Union for Conservation of Nature. The present-day Suwannee River (below) yields a clue as to what the Montbrook site may have looked like in its heyday, some 5.5 million years ago.

FROM ITS HEADWATERS IN GEORGIA, the Suwannee River meanders 246 miles south, tea-colored and wild, through some of the most remote and undeveloped parts of Florida before emptying into the Gulf of Mexico. It was in one of the fields east of the river that, in 2015, a curious 5-year-old found a peculiar fossil.

Before long, rumors of something strange turning up in rural Levy County reached paleontologist Richard Hulbert at the Florida Museum of Natural History. Hulbert was skeptical. Dig just about anywhere in the state, and you might find a prehistoric bone. Then a photo piqued his interest. The assortment of fossils was unusually diverse, even for Florida. Hulbert spotted a mix of land and aquatic animals, including fragments of two types of turtle shells, garfish scales, alligator osteoderms and the ankle bone of a gomphothere—an ancient four-tusked elephant relative.

Hulbert visited the site one afternoon in November of that year with research assistant Rachel Narducci. There, on a pine tree farm owned by Eddie Hodge, they located a pit Hodge had dug for clay to fill a rutted dirt road. Hulbert climbed inside, as Hodge’s granddaughter Timber had done before him. As he began to dig just below the surface, Hulbert immediately found fossils.

“It didn’t take us very long to realize this was a really rich site,” he says of the location subsequently coined an “elephant graveyard.”

A clandestine excavation began the next day, aiming to take stock of the site without drawing unwanted attention to the landowners or the property. The museum dubbed the site—30 miles or so southwest of Gainesville, near the city of Williston—“Montbrook” after a defunct town Hulbert found on a 1930s highway map of the area.

Nine years later, volunteer-driven excavations continue at Montbrook, which Jon Bloch, curator of vertebrate paleontology at the Florida Museum of Natural History, calls “arguably among the most significant Neogene fossil sites ever found in North America.” An estimated 5.5 million years old, the site has yielded about 80,000 fossils to date from some 135 species, including 15 to 25 that were previously unknown, according to ongoing research. Those have included animals expected in Florida, such as flamingos and alligators, as well as delightful surprises, such as saber-toothed cats, bone-crushing hyenalike dogs and a stubby extinct rhinoceros.

The array also included 3,000 gomphothere fossils from 38 separate individuals belonging to the genus Rhynchotherium—a tusk here, a leg bone there—but no complete adult specimen. That changed in 2022. Scientists say the adult male gomphothere found that year, surrounded by the remains of at least seven juveniles, could provide valuable insights about African and Asian elephants—gomphotheres’ sole surviving relatives—in an era of climate change.

As Hulbert says, “All you can do is learn from the past.”

Getting to know the gomphotheres

Weighing 1,000 pounds in its plaster jacket, one of the male’s legs alone took six people to move. The torso was even trickier, earning the gomph its nickname, Chase, after Eddie Hodge’s son, who lent his backhoe to lift the specimen out of the pit. Paleontologists estimate the male weighed around 5,000 pounds during its life and stood 8 feet tall at its shoulders—about the size of a modern African forest elephant—with upper tusks stretching more than 5 feet long.

Fossils show these gomphotheres had short, stocky limbs, more like mastodons than elephants, although their skin probably was closer to the latter. The four tusks are an oddity compared to more recent relatives. The upper set were elongated and curved, while the lower, shorter set protruded from the jaw like bucked teeth. Scientists put the animals’ lifespan at 40 to 50 years.

Gomphotheres once roamed every continent on Earth, save for Antarctica and Australia, and existed for more than 20 million years, spanning the Miocene, Pliocene and Pleistocene epochs. By 16 million years ago, they had crossed the Bering Land Bridge into North America and spread across the continent. A site in Southern California is the only other place in the United States with a density of Rhynchotherium adult and juvenile fossils similar to that of Montbrook, although their range likely stretched into Mexico. When the Isthmus of Panama formed about 2.7 million years ago, gomphotheres were waiting to cross into South America.

At Montbrook, the animals lived alongside a variety of terrestrial and aquatic species, both fresh- and saltwater. Paleontologists have identified everything from sharks, snapping turtles, predatory fish and tortoises to now-extinct camels, horses, llamas and mastodons. The presence of marine life indicates sea levels once were much higher than today, putting Montbrook closer to the coast, while freshwater fish and reptiles suggest Montbrook was part of an ancient waterway similar to the Suwannee—perhaps even its ancestral river. In sediment layers long buried by time, you can still see miragelike remnants of the river, which may have reached up to 300 feet wide.

“This would not be something that you would cross, if you were an elephant, on a daily basis,” Hulbert says. “You would have to make a decision that the vegetation on this side of the river is pretty well eaten up, and we want to go across.”

That led researchers to ask a fundamental question: How did so many animals seemingly meet their demise in the exact same spot? Montbrook, they surmise, was situated at a bend in the ancient river where debris, including carcasses, gathered. Some gomphotheres may have died while attempting to cross the river or after falling in. Others probably died upstream and washed down, while still more ended up at the spot due to flooding. The presence of partially intact or nearly complete skeletons suggests most died nearby.

“It wasn’t a catastrophic event—like, there wasn’t an asteroid that killed off the elephants at one time,” says Jeanette Pirlo, an assistant professor of evolutionary biology at California State University, Stanislaus.

What’s for sure is that over a long period—decades, centuries or longer—a steady influx of animal carcasses resulted in a massive wildlife grave. Jack Brown, a retired zoo director and museum volunteer, draws on his knowledge of wildlife behavior and anatomy to help recreate Montbrook’s ecosystem. He suggests it’s possible that flooding cut away at the riverbanks, forming deadly depressions, or “gravity wells,” along what he calls Gomphothere Beach, where animals got sucked in and drowned.

“It honestly takes a lot to kill an elephant,” he says.

Because the gomphotheres were a “jack-of-all-trades, master of none,” as Hulbert says, it’s likely that when more specialized mammoths moved south during the Pleistocene, North American gomphs were outcompeted for resources. (Researchers continue to debate how much human hunting and climate factored into the animals’ demise.) The last gomphotheres went extinct around 13,000 years ago, according to fossils discovered in Sonora, Mexico.

Tracing the past into the future

While gomphotheres are long gone, research by a handful of international scientists could offer clues on how their surviving cousins might respond to modern threats, including climate change, habitat loss and poaching.

Gomphotheres are part of the proboscidean animal group, which contains the elephant and mastodon families. If you trace the lineage of African elephants back far enough, “there’s a series of fossils going back further and further in time that eventually become gomphotheres,” Hulbert says. Only three proboscideans reached the 21st century and survive today: the African savanna elephant, the African forest elephant and the Asian elephant. Scientists estimate that fewer than 465,000 elephants total are left in the wild.

“Elephants are the last remnants of something much more diverse that existed not so long ago,” says Bloch of the Florida Museum of Natural History.

At a museum warehouse, boxes labeled “Montbrook” line the tops of cabinets brimming with fossils. Narducci, who took over as collection manager for vertebrate paleontology after Hulbert retired in 2022, opens a cabinet door and pulls out a drawer full of tiny fossils, some as thin as toothpicks, others the size of a pinky nail.

Among them sits a marble-sized specimen, smooth and light to the touch, as if filled with air. Montbrook has produced fossils of gomphotheres ranging in age from around 50 years old to infants. This one is a fetal gomphothere, Narducci explains.

“Honestly, the small fossils are almost more important than the big ones, because they can tell you more about the sediment and environment,” she says. Similar to behavior observed in today’s African and Asian elephants, gomphotheres may have visited Gomphothere Beach to eat its sand, supplementing essential minerals missing from their diet.

“The teeth are this beautiful caramel-butter yellow, shiny, gorgeous color, and then some of the other teeth that are not in the jaw yet and aren’t functional are this beautiful chocolate brown,” says Pirlo, who studies gomphothere population dynamics and diets.

Those teeth can reveal insights about diet, habitat, age, herd dynamics, behavior and how gomphotheres responded to environmental changes. Using geochemistry to extract data from the preserved carbon and oxygen isotope in tooth and tusk enamel, Pirlo’s research suggests Montbrook’s gomphotheres were herbivores that ate leaves and grasses. (Hulbert says he plans to study tooth tartar, which holds pollen and other botanical remnants that could help identify specific plants gomphotheres were eating.)

Pirlo began to notice individual gomphotheres’ dietary preferences and how those changed over a lifetime. Some adults sought out leaves over grasses, or vice versa, while teenagers tended to eat easier-to-chew plants because their teeth were smaller. “You can get really personal with the stories that come out of the site,” she says.

Plants, in turn, reveal information about a location’s environment. Montbrook’s climate likely was similar to that of Florida today, experiencing seasonal rainfall but more moderate winters and harsher dry seasons with wildfires that tamed forest undergrowth, according to Hulbert.

In the Miocene, during gomphotheres’ reign, global temperatures began to warm up. This makes gomphotheres a useful model for understanding how today’s rapid climatic changes might affect elephants, Pirlo says. “We can look at how [gomphotheres] may have adapted across that heating trend and how modern mega herbivores might also adapt their feeding and behavior.”

It’s possible conservationists eventually could use this research to shape policy regarding elephants and other animals, she says, “working with lawmakers and people who can make those changes in preserving the fauna that we have today, based on what we know from the past.”

Across the Atlantic Ocean, researchers from London’s Natural History Museum and the University of Helsinki have analyzed gomphothere teeth from Africa with climate change in mind. They measured characteristics such as tooth crown height to determine what the animals were eating and then compared those findings to palaeobotanical data, sediment cores, stable isotope records and dust accumulation in marine samples, says Juha Saarinen, a paleontologist at the University of Helsinki.

As reported in the journal Nature Ecology & Evolution, they found gomphotheres and early elephants had highly flexible diets. Early elephants “seem to be especially versatile in terms of their ecology, and I think that’s part of the reason why those particular species survived,” Saarinen says. The ability to adjust in response to changing environments led to sustained trends in dental adaptations over tens of millions of years. Those dental evolutions eventually gave the elephants an advantage over the last African gomphotheres, allowing elephants to outcompete them into extinction about 3.6 million years ago.

The scientists are currently expanding their research to determine whether the encroachment of shrubby arid zones into grasslands, driven by natural climate change, contributed to the extinction of the Palaeoloxodon, a grass-dependent early elephant, and other giant herbivores in Africa over the past million years.

“The story we ultimately tell may serve as a stark warning for how climate change will further decimate African biodiversity, if it’s left unchecked,” Steven Zhang, a researcher working under Saarinen, wrote in The Conversation.

Montbrook’s gomphotheres are less directly related to elephants than African gomphotheres, but they still provide an excellent model to help us understand how elephants might react to modern threats, says study co-author Adrian Lister, a paleontologist at London’s Natural History Museum. “If you look at it as an ecological study of the changing ecology and the impact in terms of extinction, any model system that could include the North American situation can teach us things about how species respond to climate change and why some species do better than others in response,” he says.

While the study supports the theory that flexibility helped elephants evolve and survive, today’s descendants face more than a naturally changing climate. They’re also hunted and losing their habitat—and on a timeline accelerated by humans. Unlike in the Miocene or Pleistocene, contemporary climate change is occurring over decades and centuries rather than over millennia.

“You see, things act together,” Lister says. “That’s when it becomes lethal. It’s all happening too fast for the evolutionary responses [Saarinen] and I plotted in the past,” he explains, positing that modern threats could outpace elephants’ ability to adapt.

One mark in modern elephants’ favor: the trait of living and traveling in herds, a behavior likely shared by gomphotheres, Pirlo says, based on the population size and age range of Montbrook’s fossils. She sees gomphotheres as evidence of how deeply ingrained and essential elephants’ herd dynamics and long-distance migration patterns are, with the herd carrying collective knowledge passed down through generations.

Scientific research consistently shows that, to adapt to climate change, some wildlife and plants must stay on the move. The opportunity to roam gives living organisms a better chance of finding food, water and suitable habitat. Conversely, “if we were to dwindle the size of each herd, you’re going to lose a lot of that knowledge, a lot of that tradition and culture that’s found within elephant groups,” Pirlo says. Another side effect of shrinking and disconnected habitat? A rise in human-wildlife conflicts.

Between 2020 and 2021, a herd of Asian elephants trekked more than 300 miles across China in search of food. They broke into villagers’ homes, looted crops, wandered city streets and munched on plants at a botanical garden where the Chinese Academy of Sciences (CAS) oversees thousands of species. CAS scientists looked into why the elephants were expanding their range. In a study published in Frontiers in Ecology and Evolution, the authors found correlations between climate change impacts and the elephants’ ensuing move north, sowing chaos in human-dominated habitats as they went—a problem the researchers expect will continue.

In India, where elephant habitats are shrinking and hotter summers have dried up bodies of water, similar friction occurs as elephants search for resources in areas heavily populated by humans. This dynamic could become more problematic for elephants as time goes on. If protein-rich food sources and water availability continue to diminish, “then they’re in trouble, especially when they’ve got nowhere else to go,” Lister says.

In prehistoric times, sans humans, animals living in a changing climate could follow the habitats that best suited them more easily. Brown says Montbrook is evidence that this ability to move freely resulted in rich biodiversity. Although gomphotheres ultimately were outcompeted millions of years later, he sees the presence of a seemingly thriving, migratory herd of elephant relatives as decisive support for wildlife corridors: conservation areas that protect and connect wild lands. He cites the Florida Wildlife Corridor, a statewide conservation effort that seeks to preserve and expand a network of 18 million acres of connected lands and waters, as a critical example.

Montbrook’s gomphotheres may have crossed the river seeking food at their own peril, and at the sacrifice of some, but the freedom in that choice was key to the herd’s survival.

“The elephants wandered here all the way from Asia,” Brown says, “so talk about no boundaries.”

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Stephenie Livingston has reported for Scientific American and Audubon and is a staff writer for Upward, a magazine published by the International Space Station National Laboratory. She previously worked for the University of Florida.

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