"That shows you that it's not just a natural selection of animals, because typically carnivores are far rarer than herbivores.
"These locations represent a scavenging event going on."
To understand sabertooth hunting behavior, scientists compared the numbers of modern carnivores competing for kills in eastern and southern Africa with those of mainly extinct species found in the Los Angeles fossil record.
The researchers analyzed African "playbacks," in which the recorded calls of lions, hyenas, and distressed prey were used to attract carnivores.
"If you look at what comes to the playback compared to what you expect in the environment as a whole, it's only the large, social carnivores that are really abundant," Carbone said.
This matched exactly the proportion of sabertooths and dire wolves—another prehistoric predator—found in the Los Angeles tar pits.
There was certainly an advantage to saber-toothed cats working in groups, added study co-author Blaire Van Valkenburgh, a professor of ecology and evolutionary biology at the University of California, Los Angeles.
"La Brea was an open environment with a high density of carnivores likely to encounter each other, just as you would see in Africa today," she said. "That really favors working in groups and safety in numbers."
Scott Creel, an ecology professor at the Montana State University in Bozeman, is skeptical about the abundance of large, social carnivores attending the playbacks in Africa.
"I think it is important to consider whether other species did not attend because they were solitary, or did not attend because they were smaller," said Creel, who was not involved with the study.
"In modern African carnivore communities, all of the other species that might respond are substantially smaller than lions.
"[So] it is perhaps not surprising that the great majority of smaller species are not attracted to playbacks that include a lot of lion roars, regardless of their social system," he added.
But Christian Kiffner, a carnivore-ecology expert at the University of Göttingen in Germany, said the conclusions drawn from comparing the Africa playback studies and the California fossil record are valid.
"The two scenarios should be quite similar," said Kiffner, who was also not involved with the study.
He agreed with Creel, however, in that the playback methodology favors large, social carnivores—but only slightly.
Solitary carnivores such as leopards, for instance, will almost only respond to prey distress calls, but not to hyena calls.
Carbone, the lead author, says there is still much to learn about the social behavior of sabertooths.
"But we're getting more and more evidence to support sociality in these cats," he said.
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