From about 1.65 million until 10,000 years ago, was the period called “Pleistocene Epoch”. At that time various types of animals occupied the area that is now the mid-western United States. Most of these types of animals are no longer found in the area. Some of these animals are extinct. Some others are still around but no longer occur in the area. Most of what we know about these animals comes from sites that date between 40,000 and 10,000 years ago (the last Ice Age). This is because sites older than 40,000 years old are less common than younger sites. Many animals in North America went extinct shortly after the end of the last Ice Age, about 12,000 years ago. These were mostly mammals larger than approximately 44 kg (about 100 pounds). Some of the animals that went extinct are well known (like saber-toothed cats, mammoths, and mastodons). Other animals went extinct millions of years earlier, during the Pleistocene. Many of these are large animals, and are referred to as megafauna. Little of the North American megafauna survive -- some examples include bears and American Bison. Before this extinction the diversity of large mammals in North America was similar to that of modern Africa. As a result of the extinction, relatively few large mammals are now found in North America.
What are some extinct animals?
Some of the fascinating extinct animals that lived in North America include:
The famous Saber-toothed tiger, which was a top predator in Pleistocene North America
The Wooly Mammoth, with adaptations to Ice Age living, is often found frozen in Canadian permafrost
The American Cheetah, a cheetah-like animal more closely related to the modern Puma, and which is known only from bone fragments
American Lion, which is the largest subspecies of lion ever to have existed, and is 25% larger than the African lion (extinct 8,000 BC)
Ancient Bison, which was the most numerous large herbivore for 8,000 years until it went extinct around 8,000 BC. An herbivore is an animal which only eats material which is of plant origin
Cuvieronius, a large elephant with spiral tusks (extinct 7,000 BC)
American mastodon (scientific name Mammut americanum) roamed North America from at least 3.75 million to 11,000 years ago. Mastodons, along with mammoths and modern elephants, are members of the order Proboscidea. As adults they stood between 2.5 and 3 meters (8-10 feet) at the shoulder and weighed betweeen 3500 and 5400 kilograms (4-6 tons). Mastodons became extinct approximately 11,000 years ago. Today, paleontologists are trying to understand why. The mammoths are closely related to the living elephants, especially to the Asiatic elephant (Elephas maximus)
Snowshoe hare (Lepus americanus) is a medium-sized rabbit. Its name comes from the fact that the animal's hind feet are very long and the toes can be spread out to act like snowshoes. These large feet also have fur on the soles which protects them from the cold and increases traction
Muskoxen inhabited the midwestern U.S. during the last Ice Age: the muskox (Ovibos moschatus) and the extinct woodland muskox (Bootherium bombifrons). Ovibos moschatus is the same muskoxen still found in the artic today(map on the right). Modern Ovibos stand about 130 cm (4 ft) tall at the shoulder and usually weigh anywhere from 200 to 410 kg (440 to 900 lbs)
Jaguars: Most people associate the jaguar (scientific name Felis onca) with Central and South America. Indeed, its historic range includes much of Central and South America as well as parts of Mexico and portions of the extreme southern United States. During the last Ice Age, however, this large cat was also found in much of the southern half of the United States
Dire Wolf, a large wolf that went extinct in 8000 BC
Giant Beaver, with a length of up to 2.5 m (8.2 ft) that lived around the Great Lakes until 10,000 years ago
Giant Hutia, a rodent that could grow to the size of bears, which lived in Puerto Rico until just 3,000 years ago. Except for the Ancient Bison and the Dire Wolf, few of these extinct animals have living relatives
Giant Short-Faced Bear, which is the largest bear that ever lived, standing at seven feet tall and ten feet long (extinct 10,500 BC)
Ground Sloths: Four species of ground sloths inhabited the United States at the end of the last Ice Age. These were Jefferson's ground sloth (Megalonyx jeffersonii), Laurillard's ground sloth (Eremotherium laurillardi), the Shasta ground sloth (Nothrotheriops shastensis), and Harlan's ground sloth (Glossotherium harlani). Of these four only two, Jefferson's and Harlan's ground sloths, are found in the mid-western U.S
Saber-toothed cats: Saber-toothed cats are some of the best known and most popular of all Ice Age animals. They are among the most impressive carnivores ever to have lived. Two different types of saber-toothed cats lived in the midwestern U.S. at the end of the last Ice Age. One type was the familiar sabertooth, represented by the genus Smilodon. These cats had enlarged canines usually associated with the name sabertooth. Their canines were up to 18 centimeters (7 inches) long, and
Glyptodon, an armadillo (small mammal )-like armored animal about the size of a VW Bug, which originally evolved in South America but moved to Texas
Why did these animals become extinct after the last Ice age?
Scientists who study the extinction have identified three major mechanisms that may have caused the extinction. These three causes are
Hyperdisease: The third hypothesis to account for large scale extinctions at the end of the Pleistocene era is based on the idea of hyperdiseases, which are highly infectious diseases.
Weather Change: About 18,000 years ago the climate and environments of North America were changing rapidly. Temperatures were warming. Rainfall patterns were changing. These climate changes were causing fundamental changes in the ecosystems of North America. Plants and animals were moving out of areas they had lived in and into new areas. Communities were coming apart and reorganizing. Many scientists think that these climatic and ecosystem changes caused the extinctions at the end of the Pleistocene.
Human hunting: Just after 14,000 years ago human migrants from Asia entered the New World. They may have been the first people to set foot in North America. These people hunted and gathered wild animals and plants. The animals they hunted included many that became extinct.