Researchers at the University of Cincinnati studied the teeth of prehistoric horses and bison in the Arctic to learn more about their diet compared to modern species.
What they discovered suggests that the Arctic 40,000 years ago maintained a greater diversity of plants which, in turn, supported both growing numbers and more diverse animals.
The Arctic today is spartan compared to the wildlife-rich landscape during the ice ages of the Pleistocene era, between 12,000 and 2.6 million years ago, when wild horses, mammoths, bison and other large animals roamed the steppes and grasslands of what is now northern Canada, northern Europe, Alaska and Siberia. Short-faced bears, land sloths, and even cave lions have called the 49th state home.
The Arctic was also home to larger populations, even compared to today’s spectacular caribou herds, which can number over 750,000 animals. The region was home to six to ten times as many large animals as today’s Arctic.
“In the Pleistocene, the diversity of the fauna was so much greater than what we see today,” said Joshua Miller, assistant professor at UC. “It looked completely different. A key question is why the Arctic is so impoverished in comparison today?”
The study was published in the journal Paleogeography, paleoclimatology, paleoecology.
Researchers studied two of the most common large animals living between 12,000 and 40,000 years ago in what is now Alaska: horses and the steppe bison, both of which have become extinct due to climate change, hunting. human or a combination of the two.
UC doctoral student and senior author Abigail Kelly made dental casts of fossil specimens obtained from the University of Alaska Museum and submitted the fossil teeth for dental wear analysis to assess diet. of these extinct animals.
“Because foods have different textures and interact with the enamel surface in different ways, we can look at different diets,” Kelly said.
The teeth of herbivorous animals show different signs of wear depending on the type of food they chew. Grass is particularly abrasive because it contains silica which can wear down the teeth over time. To the naked eye, herbivorous animals have teeth with more blunt wear patterns (called mesowear). When viewed under a microscope, the teeth show parallel stripes. Animals that eat less grass and more leaves of trees, grasses, and shrubs have relatively sharper teeth with fewer microscopic scratches.
UC researchers found that the steppe bison’s tooth wear patterns had fewer scratches than the modern plains bison, which mainly eats grass but more scratches than the European bison, which likely feeds more woody plants. Likewise, prehistoric horses had teeth that bore different wear patterns than modern horses, suggesting that their diet contained less abrasive grasses. Prehistoric bison and horses likely had a more varied diet rich in broadleaf herbaceous plants than bison and horses today, but researchers said the micro-wear patterns may reflect seasonal foods. that the animal ate in the months preceding its death.
The study suggested that the Arctic had a larger vegetation mix than exists today.
“It seemed like the diets of the bison and the horses weren’t that different. They ate foods of similar texture,” Miller said. “But their physiology is quite different. Bison are foregut fermenters that digest food differently from hindgut fermenters like horses. So it is possible that species get different levels of nutrition from the same. food.”
The study is of pressing importance to the conservation of the wood bison, which was hunted to extinction in the United States in the 1900s. Populations from Canada were reintroduced to Alaska in 2015. The largest animal North American land bison, the wood bison, are a descendant of the plains bison that migrated north about 10,000 years ago and briefly coexisted with the steppe bison before replacing it.
Biologist and study co-author Tom Seaton is overseeing the reintroduction of the wood bison for the Alaska Department of Fish and Game. He said their analysis offers important insights into the coexistence of various herbivore populations in the Alaskan landscape thousands of years ago, which could help biologists understand the needs of the wood bison today. ‘hui.
Steppe bison have survived thousands of years longer than horses, even though both relied on similar foods, according to UC’s dental analysis.
But it is likely that bison and horses evolved to use landscape resources in different ways – a phenomenon known as “niche partitioning.” Horses and bison also have significant differences in the way they digest food.
“This study provides information for the Alaskan Wood Bison Restoration Project through niche compartmentalization perspectives between large herbivores on the modern Alaskan landscape,” Seaton said. “I hope this study provides one more piece in the bison restoration puzzle in the north.”
While grazers like horses and bison have disappeared in the Arctic, grazers like moose and caribou that feed primarily on leaves and woody plants still persist.
“What’s interesting is why it’s the grazers that go out as the browsers go through it,” Miller said.
Miller has led numerous research expeditions deep into the Arctic National Wildlife Area by rigid inflatable boat to collect caribou antlers to track their historic migrations.
“The impacts of climate on vegetation can create sudden change,” he said. “The cooler and drier environments of the late Pleistocene allowed megafauna to thrive. But the hot and humid climates of the Holocene led to the humid tundra vegetation of today.”
For her next project, doctoral student Kelly will take a closer look at the bison and horses of the Yukon that lived around the same time.
“We will focus on the story of how bison have responded to environmental changes over the past 50,000 years, as northern climates have moved from relatively mild to extremely cold and dry conditions during the last Ice Age, and and finally to the rapid warming of the boreal forest. forest climate we see today, ”she said. “Are bison able to modify their diet in response to changing vegetation, or are they stuck in a single doghouse?”