December 27th, 2012 by James Ayre
American lions and saber-toothed cats didn’t die out from starvation as had been previously theorized, new research has revealed. In the years directly before they died out in North America they were apparently eating very well the research has shown.
“That is the conclusion of the latest study of the microscopic wear patterns on the teeth of these great cats recovered from the La Brea tar pits in southern California. Contrary to previous studies, the analysis did not find any indications that the giant carnivores were having increased trouble finding prey in the period before they went extinct 12,000 years ago.”
This research directly “contradicts previous dental studies and presents a problem for the most popular explanations for the Megafaunal (or Quaternary) extinction when the great cats, mammoths and a number of the largest mammals that existed around the world disappeared.”
“The popular theory for the Megafaunal extinction is that either the changing climate at the end of the last Ice Age or human activity — or some combination of the two — killed off most of the large mammals,” said Larisa DeSantis, assistant professor of earth and environmental sciences at Vanderbilt, who headed the study. “In the case of the great cats, we expect that it would have been increasingly difficult for them to find prey, especially if had to compete with humans. We know that when food becomes scarce, carnivores like the great cats tend to consume more of the carcasses they kill. If they spent more time chomping on bones, it should cause detectable changes in the wear patterns on their teeth.”
About 20 years ago a researcher at UCLA published a study done on the levels of tooth breakage in the large carnivores near the estimated time of their extinction. The analysis was done specifically on the teeth of “American lions, saber-tooth cats, dire wolves and coyotes from La Brea.” The researcher found that there was, roughly, 3 times more broken teeth among the predators of that time period compared to the previous ones, concluding, that “these findings suggest that these species utilized carcasses more fully and likely competed more intensely for food than present-day large carnivores.”
“The latest study uses a new technique, called dental microwear texture analysis (DMTA), developed by co-author Peter Ungar at the University of Arkansas. It uses a confocal microscope to produce a three-dimensional image of the surface of a tooth. The image is then analyzed for microscopic wear patterns. Chowing down on red meat produces small parallel scratches. Chomping on bones adds larger, deeper pits. Previous methods of dental wear analysis relied on researchers to identify and count these different types of features. DMTA relies on automated software and is considered more accurate because it reduces the possibility of observer bias.”
“DeSantis and Ungar, with the assistance of Blaine Schubert from East Tennessee State University and Jessica Scott from the University of Arkansas, applied DMTA to the fossil teeth of 15 American lions (Panthera atrox) and 15 saber-tooth cats (Smilodon fatalis) recovered from the La Brea tar pits in Los Angeles.”
“Their analysis revealed that the wear pattern on the teeth of the American lion most closely resembled those of the present-day cheetah, which actively avoids bones when it feeds. Similarly, the saber-tooth cat’s wear pattern most closely resembled those of the present-day African lion, which indulges in some bone crushing when it eats. (This differs from a previous microwear study using a different technique that concluded saber-tooth cats avoided bone to a far greater extent.)”
“The researchers examined how these patterns changed over time by selecting specimens from tar pits of different ages, ranging from about 35,000 to 11,500 years ago. They did not find any evidence that the two carnivores increased their ‘utilization’ of carcasses throughout this period. If anything, their analysis suggests that the proportion of the carcasses that both kinds of cats consumed actually declined toward the end.”
“The researchers acknowledge the high rate of tooth breakage reported in the previous study, but they argue that it is more likely the result of increased breakage when taking down prey instead of when feeding.”
“Teeth can break from the stress of chewing bone but they can also break when the carnivores take down prey,” DeSantis pointed out. “Species like hyenas that regularly chew and crack bones of their kills are as likely to break the rear teeth they use for chewing as their front canines. Species like the cheetah, however, which avoid bones during feeding are twice as likely to break canines than rear teeth. This suggests that they are more likely to break canines when pulling down prey.”
“The researchers report that previous examinations of the jaws of the American lions and saber-tooth cats from this period found that they have more than three times as many broken canines and interpret this as additional evidence that supports their conclusion that most of the excess tooth breakage occurred during capture instead of feeding.”
“In addition, the researchers argue that the large size of the extinct carnivores and their prey can help explain the large number of broken teeth. The saber-toothed cats were about the size of today’s African lion and the American lion was about 25 percent larger. The animals that they preyed upon likely included mammoths, four-ton giant ground sloths and 3,500-pound bison.”
“Larger teeth break more easily than smaller teeth. So larger carnivores are likely to break more canine teeth when attempting to take down larger prey, the researchers argue. They cite a study that modeled the strength of canine teeth that found the canines of a predator the size of fox can support more than seven times its weight before breaking while a predator the size of lion can only support about four times its weight and the curved teeth of the saber-toothed cats can only support about twice its weight.”
“The net result of our study is to raise questions about the reigning hypothesis that “tough times” during the late Pleistocene contributed to the gradual extinction of large carnivores,” DeSantis summarized. “While we can not determine the exact cause of their demise, it is unlikely that the extinction of these cats was a result of gradually declining prey (due either to changing climates or human competition) because their teeth tell us that these cats were not desperately consuming entire carcasses, as we had expected, and instead seemed to be living the ‘good life’ during the late Pleistocene, at least up until the very end.”
The new research was just published on December 26th in the scientific journal PLOS ONE.
Some more information on American Lions and Saber-toothed Cats:
“The American lion (Panthera leo atrox or P. atrox) — also known as the North American lion, Naegele’s giant jaguar or American cave lion — is an extinct lion of the family Felidae, endemic to North America and northwestern South America during the Pleistocene epoch (0.34 mya to 11,000 years ago), existing for approximately 0.33 million years. It has been shown by genetic analysis to be a sister lineage to the Eurasian cave lion (Panthera leo spelaea or P. spelaea). The American lion is one of the largest types of cat ever to have existed, slightly larger than the Early Middle Pleistocene primitive cave lion, P. leo fossilis and about 25% larger than the modern African lion.”
“A saber-toothed cat (alternatively spelled sabre-toothed cat), also known as a saber-toothed tiger, is any of various groups predatory mammals related to modern cats (or resembling cats) that were characterized by long, sabre-shaped canine teeth. These animals belonged to subfamilies of Machairodontinae (Felidae), Barbourofelidae and Nimravidae (both Feliformia) as well as two families related to marsupials that were found worldwide from the Eocene Epoch to the end of the Pleistocene Epoch (42 mya—11,000 years ago), existing for approximately 42 million years. The large maxillary canine teeth extended from the mouth even when it was closed. Despite the name, not all animals known as saber-toothed cats were closely related to modern felines.”
“The Nimravidae are the oldest, entering the landscape around 42 mya and becoming extinct by 7.2 mya. Barbourofelidae entered around 16.9 mya and were extinct by 9 mya. These two would have shared some habitats.”
Source: Vanderbilt University
Image Credits: Mauricio Anton/ DeSantis LRG, Schubert BW, Scott JR, Ungar PS (2012) Implications of Diet for the Extinction of Saber-Toothed Cats and American Lions. PLoS ONE 7(12): e52453. doi:10.1371/journal.pone.0052453; Vanderbilt University
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