Question Answered by Dr. Kari Prassack, Lead Paleontologist at Hagerman Fossil Beds National Monument
The Hagerman Fossil Beds are part of the Pliocene Epoch (5.3-2.6 million years ago) and date from about 4 million to 3 million years ago. This is the time just before the ice ages of the Pleistocene Epoch, and Idaho was much warmer and wetter than it is today. The animals that lived back then reflect a variety of habitats, as seen in a paleo-artist’s reconstruction below. A lake, river, and widespread wetlands supported animals like fish, clams, beavers, ducks, otters, and turtles. In open grasslands, coyotes stalked voles while pronghorns grazed. The surrounding forests supported climbers and roosters, like raccoons and owls, and browsers, like camels. These are just a few of the 200 species of animal that we know lived alongside the Hagerman horse (Equus simplicidens).
Many of these animals have descendants living right here in Idaho today. Those animals, like beavers, marmots, and cormorants, were able to adapt to a changing environment. Others, like the camel and peccary, had to leave North America in search of new lands that better fit their needs. They headed to faraway lands including Africa and South America! The horse was one of those animals. Horses migrated from North America into Asia, Europe, and Africa, went extinct here in North America at the end of the Pleistocene, and were only re-introduced here a few hundred years ago by humans.
Perhaps most exciting are the animals that went extinct and have no living descendants. What did they eat? How did they move? Why did they die? These are just some of the questions paleontologists like to investigate. Extinct beasts from Hagerman include a giant ground sloth that stood up nine feet tall to reach the best leaves, a bone-crushing borophagine dog with jaws like a hyena, a badger-like creature called Ferinestrix that was the size of a wolverine, and two species of saber-toothed cat, both of which likely stalked our Hagerman horse for a tasty dinner.
Looking back at the animals of Hagerman Fossil Beds that adapted, migrated, or went extinct we can wonder the fate of today’s species. Will some descendent of today’s coyote be out stalking rodents 100, 10,000 or 1,000,000 years from now? Will marmots grow to unusually large sizes? Will camels return to Idaho? How might a change in climate change the types of animals you see here today?
The Hagerman Horse
Did you know that horses evolved in North America? The Hagerman Horse, Equus simplicidens, was a bit smaller than the size of a modern horse. Its bones most closely resemble Grevy’s zebra for comparision purposes, but it wasn’t a zebra.
Hagerman horses are important for understanding horse evolution. Modern horses (and zebras) and all fossil horses of the genus Equus have a single hoof, but horses have been around for 55 million years and the ancient ancestors of today’s equids had a few extra toes. The modern grassland biome first appeared during the Miocene (23.03 to 5.332 million years ago) and this change of the landscape triggered a response in the horse: a reduction in toes meant a gain in speed and endurance on the open plains. Running is a good technique to get away from pursuit predators like wolves and cheetahs. (from https://www.nps.gov/hafo/)
- Remove your shoes and stand on one foot. Lift your toes of your standing foot off the ground so that you’re only using foot muscles to balance, with no help from the toes. Is it easier to balance with or without toes? How did toes help you balance? Ancient horses living in the wetter forest environment spread their toes for stability as they looked for food or ran from predators.
- Now stand on your tiptoes like a ballerina. Modern horses have on toe, which is faster for running on dry grasslands. One thicker toe is stronger and less prone to injury than smaller, thinner toes.