Smilodon: The Sabre-Toothed Cat of the Ice Age Americas

Smilodon was a powerful sabre-toothed cat that lived in North and South America from about 2.5 million to roughly 10,000 years ago. Famous for its long, blade-like upper canines, it hunted large Ice Age animals such as bison, horses and young mammoths. Thousands of its fossils from the La Brea Tar Pits in Los Angeles have made it one of the best-known prehistoric predators in the world.

Background: the sabre-toothed cats

Sabre-toothed predators evolved several times in the history of mammals. Smilodon belonged to the Machairodontinae, an extinct subfamily of the true cat family (Felidae) that included other sabre-toothed and scimitar-toothed cats in Africa, Eurasia and the Americas. Despite the popular name “sabre-toothed tiger”, it was not a tiger and has no close living relatives.

The genus name was coined in 1842 by the Danish naturalist Peter Wilhelm Lund, from fossils found in caves near Lagoa Santa in Brazil. It is usually translated as “knife tooth” or “scalpel tooth”, from Greek words for a carving knife and a tooth.

Three species

Palaeontologists generally recognise three species:

• Smilodon gracilis, the smallest and earliest, lived in North America from about 2.5 million to around 500,000 years ago.
• Smilodon fatalis lived in North America and along the western side of South America from roughly 1.6 million years ago until the end of the last Ice Age. It is the species found at La Brea.
• Smilodon populator, the largest, lived in eastern South America from about 1 million years ago. It descended from North American ancestors that crossed into South America during the Great American Biotic Interchange.

Anatomy

Smilodon was built more like a bear than a lion. It had a deep chest, very muscular forelimbs, a short tail and a relatively short lower back. Its upper canines were long, flattened from side to side and finely serrated. In Smilodon populator they reached about 28 centimetres including the root.

To use these teeth, the cat could open its jaws to an angle of about 110 to 120 degrees, far wider than a modern lion. Powerful neck muscles helped drive the canines downwards. Computer models of its skull suggest that its jaw bite was relatively weak for an animal of its size, so the force of the strike came largely from the head and neck.

Figures are estimates and vary between studies.

Hunting style

Most researchers think Smilodon was an ambush predator. It probably stalked or waited for large prey, then used its strong forelimbs to wrestle the animal down and hold it still. Only then could it risk a precise bite to the throat, which would cut major blood vessels and the windpipe. The long canines were vulnerable to breaking if they struck bone or were twisted by a struggling animal.

Its likely prey included bison, horses, camels, deer, ground sloths and young mammoths and mastodons. Chemical analyses of bones and teeth from La Brea suggest that Smilodon there favoured large herbivores in more wooded habitats, unlike the dire wolves that hunted in open country.

Whether Smilodon lived in groups is debated. Many La Brea skeletons show healed injuries, including serious fractures, which some scientists interpret as evidence that injured animals were fed or tolerated by others. Others argue that solitary cats can also survive such injuries.

The La Brea fossils

No site has produced more Smilodon fossils than Rancho La Brea in Los Angeles. There, natural asphalt seeping to the surface trapped animals for tens of thousands of years. A trapped horse or bison would attract predators and scavengers, which in turn became stuck. Excavations since the early twentieth century have recovered remains representing more than 2,000 individual Smilodon.

These fossils allow scientists to study growth from cubs to adults, injuries, disease and variation in size. Smilodon fatalis is today the official state fossil of California.

Discovery and study

Lund’s Brazilian fossils, found while he was exploring limestone caves in Minas Gerais in the 1830s and 1840s, introduced Smilodon to science. In North America, the American anatomist Joseph Leidy described a sabre-toothed cat from Texas in the late 1860s under a different genus name; the species name he chose, fatalis, was later transferred to Smilodon.

For decades the animal was known mostly from scattered bones. That changed in the early twentieth century, when scientists recognised the scale of the fossil deposits at Rancho La Brea. Within a few years, museum excavations had collected so many Smilodon bones that researchers could compare hundreds of skulls, jaws and limb bones from a single population.

Modern methods have added new detail. Computed tomography (CT) scans and engineering models have been used to test how the skull handled stress during a bite. Studies of tooth wear, bone chemistry and growth patterns have shed light on diet, habitat and how quickly cubs developed. Ancient DNA recovered from Smilodon fossils has confirmed that the sabre-toothed cats form a lineage that split from the ancestors of modern cats many millions of years ago.

Extinction

Smilodon disappeared at the end of the last Ice Age. The youngest reliable dates fall roughly between 13,000 and 10,000 years ago. Its disappearance was part of the wider Quaternary megafauna extinction, in which the Americas lost mammoths, mastodons, horses, camels, ground sloths and many other large animals.

As a specialist hunter of big prey, Smilodon was probably vulnerable when those prey animals declined. Rapid climate change, changes in vegetation and hunting by newly arrived humans have all been proposed as causes of the wider extinctions. Scientists debate their relative importance, and the answer may have differed from region to region.

Myths and facts

• Myth: Smilodon was a tiger. It was a member of the cat family, but from an extinct branch, not a relative of tigers.
• Myth: It lived alongside dinosaurs. Smilodon appeared more than 60 million years after the non-bird dinosaurs died out.
• Myth: It stabbed prey with its mouth closed. Its jaws had to open very wide to clear the canines; the teeth were used in a controlled bite, not as daggers.
• Fact: It overlapped with humans. People were living in the Americas by at least about 15,000 years ago, so the two would have met.

Timeline

• c. 2.5 million years ago: Smilodon gracilis appears in North America.
• c. 1.6 million years ago: Smilodon fatalis appears (estimates vary).
• c. 1 million years ago: Smilodon populator is present in South America.
• c. 50,000 to 11,000 years ago: Smilodon fatalis is repeatedly trapped in the La Brea asphalt seeps.
• c. 13,000 to 10,000 years ago: Smilodon dies out.
• 1842: Peter Wilhelm Lund names the genus Smilodon from Brazilian cave fossils.
• 1913 to 1915: Large-scale excavations at Rancho La Brea recover many Smilodon skeletons.

Why it matters

Smilodon is the most famous symbol of the lost Ice Age world of the Americas. Its fossils, especially those from La Brea, give an unusually detailed picture of how a large predator lived, fought and grew. Its extinction remains a key part of the debate over why so many great animals disappeared just as humans spread across the planet.