The teeth of ancient predators trapped in the La Brea Tar Pits are helping scientists understand why Americans have coyotes dumping over garbage cans and not saber-toothed cats ripping our arms off.
Larisa DeSantis, an associate professor of biological sciences at Vanderbilt University, grew up visiting the one-of-a-kind fossil site in Los Angeles, which contains fossils of predators that tried to eat horses, bison, and camels stuck in the tar over the past 50,000 years and became trapped themselves. The site offers the best opportunity to understand Ice Age animals facing climate change, researchers say.
Trapped in the tar
The Pleistocene Epoch spanned 2.6 million years ago to about 10,000 years ago, encompassing multiple glacial and interglacial periods and the arrival of humans, one or both of which forced predators to adapt their diets or die.
DeSantis spent the last decade visiting La Brea, studying the teeth of extinct species such as American lions, saber-toothed cats, and dire wolves; and teeth from ancient animals whose offspring are still alive today, such as gray wolves, cougars, and coyotes. Her work reveals that competition for prey among carnivores wasn’t a likely cause of the Pleistocene megafaunal extinction as formerly believed, because, like dogs and cats of today, one preferred running after herbivores in the open fields, while the other preferred stalking them in forested areas.
“Isotopes from the bones previously suggested that the diets of saber-toothed cats and dire wolves overlapped completely, but the isotopes from their teeth give a very different picture,” says DeSantis.
“The cats, including saber-toothed cats, American lions, and cougars, hunted prey that preferred forests, while it was the dire wolves that seemed to specialize on open-country feeders like bison and horses. While there may have been some overlap in what the dominant predators fed on, cats and dogs largely hunted differently from one another.”
The end of saber-toothed cats
To study these ancient predators, she uses dentistry—taking molds of the teeth and shaving off tiny bits of enamel for chemical analysis. Information about everything the animal ate lies within the isotopes, she says. Further, the microscopic wear patterns on teeth can clarify who was eating flesh or scavenging on bones.
It’s likely that those giant predators went extinct due to climate change, the arrival of humans to their environment, or a combination of the two, she says, and her team is working to clarify the cause of the extinction with several colleagues at six institutions as part of a separate ongoing study.
What they know is predators alive today in the Americas were better able to adapt their diets. Instead of only feeding on large prey, they could effectively hunt small mammals, scavenge what they could from carcasses, or do both.
“The other exciting thing about this research is we can actually look at the consequences of this extinction,” DeSantis says. “The animals around today that we think of as apex predators in North America—cougars and wolves—were measly during the Pleistocene. So when the big predators went extinct, as did the large prey, these smaller animals were able to take advantage of that extinction and become dominant apex-predators.”
A paper on the research appears in Current Biology.
The National Science Foundation supported the work.
Source: Vanderbilt University