Until about 10,000 years ago, the saber-tooth cat Smilodon fatalis was a fearsome predator in what is now the American West. More than 3,000 fossilized cats have been pulled from the acrid ooze of the La Brea tar pits in California, and researchers studying them have long pictured Smilodon as a lion-like hunter, chasing bison and horses out on open grasslands.
But now, analyses of hundreds of teeth from La Brea are painting a vastly different picture of this prehistoric terror, which could weigh up to 600 pounds and sported seven-inch-long canine teeth.
“The iconic images you see of saber-tooth cats taking down bison, that’s actually not supported at all,” says study leader Larisa DeSantis, a paleontologist at Vanderbilt University in Nashville, Tennessee. The research, published today in the journal Current Biology, provides evidence that Smilodon may instead have been a forest dweller that primarily feasted on leaf-browsing creatures.
“[They] were more likely to be taking things like tapirs and deer, as opposed to horses and bison,” DeSantis says.
Her team’s comprehensive study also helps to explain why smaller predators such as coyotes and grey wolves were able to survive to the modern day, while larger carnivores such as saber-tooth cats, dire wolves, and American lions all went extinct 10,000 to 12,000 years ago. (Also find out about a type of saber-tooth cat that may have encountered the first humans migrating into Europe.)
The key, her team suggests, was dietary flexibility following the disappearance of many of North America’s large prehistoric herbivores, such as giant ground sloths, mammoths, mastodons, and camels. For instance, previous work found that coyotes got 20 percent smaller after the herbivore extinction event, and the new look at their teeth shows that they also adjusted their lifestyles to adapt to their new reality.
“When the large predators and prey go extinct, not only do they shrink, but they fundamentally change their diet and start scavenging to become the opportunists we know today,” DeSantis says.
Handle the tooth
The scientists studied more than 700 fossil teeth collected from La Brea that once belonged to various herbivores as well as saber-tooth cats, American lions, dire wolves, cougars, coyotes, and grey wolves. The team looked at both microscopic patterns of wear, which give an indication of the types of foodstuffs the creatures were chewing on, as well as the proportions of two carbon isotopes within the tooth enamel.
These two slight variants of the carbon atom build up in plants at different rates within forested versus open environments. Herbivores that eat those plants then carry a chemical clue to their preferred habitats within their bodies, something that gets carried over into any carnivores that prey upon them. This means that the remains of carnivores can reveal whether they were eating prey that lived in forested or more open habitats.
Previous studies had looked at the proportion of carbon and nitrogen isotopes in the remains of a protein called collagen found in the bones of predators at La Brea. Those papers came to the conclusion that the largest of the predators—including Smilodon, dire wolves, and American lions—were all likely hunting in open environments.
“All of the data up until this point showed they were competing for similar prey,” DeSantis says. Some experts therefore proposed that this rivalry for resources may have contributed to their extinction. But using tooth enamel is now regarded as the “gold standard” for these kinds of isotope tests, DeSantis says.
“Tooth enamel is more reliable than collagen,” says Julie Meachen, a paleontologist at Des Moines University in Iowa who was not on the study team. That’s because enamel is less likely to be altered during the fossilization process or by spending a long time underground.
And “when we look at the enamel, we get a totally different picture,” DeSantis says. “We find that the saber-tooth cats, American lions, and cougars are actually doing what cats typically do, which is hunting within forested ecosystems and using cover to potentially ambush their prey.”
By contrast, their canine counterparts, including the dire wolves, coyotes, and grey wolves, were the ones hunting in more open environments.
“The cats and dogs partition out what they are doing,” she says.
Optimized to survive
The results suggest there was actually much less competition for prey among the region’s largest Pleistocene carnivores, particularly between the saber-tooth cats and dire wolves.
The new study is significant “because it is the first paper to show that Smilodon and dire wolves were really doing something different in terms of prey choices,” Meachen says. “It makes sense that Smilodon would hunt in a more closed environment, considering they likely did not chase prey for any appreciable distance. They were ambush predators, based on their body morphology.”
The paper “adds to our understanding of who Smilodon fatalis was and where it preferred to hang out,” adds paleontologist Christopher Shaw, an affiliate curator at the Idaho Museum of Natural History and a former collections manager at the La Brea Tar Pits and Museum. Other evidence suggests Smilodon were eating bison some of the time at La Brea, he says, but this may not be as contradictory as it seems.
“At one time, there was a subspecies of bison that was adapted to and lived in woodland habitats and may well have been ideal prey,” Shaw says.
Critically, the study adds to evidence that highly specialized prey preferences is what likely doomed species such as Smilodon and the dire wolves, while coyotes managed to survive the ecological shift by being highly flexible and taking prey as small as rats or rabbits, in addition to scavenging.
Coyotes, Meachen says, “can change their prey and even prey-killing strategy to optimize chances of survival.”