News for faculty and staff

Contact | Past Issues

Week of November 12, 2012

Research


Saber-toothed cats and bear dogs: How they made cohabitation work

The fossilized fangs of saber-toothed cats hold clues to how the extinct mammals shared space and food with other large predators nine million years ago.

Led by U-M and the Museo Nacional de Ciencias Naturales in Madrid, a team of paleontologists has analyzed the tooth enamel of two species of saber-toothed cats and a bear dog unearthed in geological pits near Madrid. Bear dogs, also extinct, had dog-like teeth and a bear-like body and gait.

This illustration depicts how the region of Cerro de los Batallones in central Spain likely looked nine million years ago. Researchers led by U-M have used carbon records in the teeth of fossilized predators to shed light on how saber-toothed cats and bear dogs shared space and prey during the late Miocene period. Photo by Mauricio Antón.

The researchers found that the cat species — a leopard-sized Promegantereon ogygia and a much larger, lion-sized Machairodus aphanistus — lived together in a woodland area. They likely hunted the same prey — horses and wild boar. In this habitat, the small saber-toothed cats could have used tree cover to avoid encountering with the larger ones. The bear dog hunted antelope in a more open area that overlapped the cats’ territory, but was slightly separated.

“These three animals were sympatric — they inhabited the same geographic area at the same time. What they did to coexist was to avoid each other and partition the resources,” says Soledad Domingo, a postdoctoral fellow at the U-M Museum of Paleontology. Domingo is first author of a paper on the findings published in the Nov. 7 edition of Proceedings of the Royal Society B.

Millions of years before the first humans, the predators lived during the late Miocene Period in a forested area that had patches of grassland. Large carnivores such as these are rare in the fossil record, primarily because plant-eating animals lower on the food chain have outnumbered meat-eaters throughout history.

Cerro de los Batallones, where Domingo has been excavating for the past eight years, is special. Of its nine sites, two are ancient pits with an abundance of meat-eating mammal bones. Agile predators, the researchers say, likely leapt into the natural traps in search of trapped prey.

“These sites offer a unique window to understand life in the past,” Domingo says.

To arrive at their findings, the researchers conducted what’s called a stable carbon isotope analysis on the animals’ teeth. Using a dentist’s drill with a diamond bit, they sampled teeth from 69 specimens, including 27 saber-toothed cats and bear dogs. The rest were plant-eaters. They isolated the carbon from the tooth enamel. Using a mass spectrometer, which one could think of as a type of scale, they measured the ratio of the more massive carbon 13 molecules to the less-massive carbon 12. An isotope is a version of an element that contains a different number of neutrons in its nucleus.

Carbon 12 and 13 are both present in the carbon dioxide that plants take in during photosynthesis. Different plants make use of the isotopes in different ways, and so they retain different amounts of them in their fibers. When an herbivore eats a plant, that plant leaves an isotopic signature in the animal’s bones and teeth. The signature travels through the food chain and can be found in carnivores as well.

“This would be the same in your tooth enamel today,” Domingo says. “If we sampled them, we could have an idea of what you eat. It’s a signature that remains through time.”

Because the researchers can tell what the herbivores ate, they can surmise what their habitat was like. They believe the animals in this study lived in a wooded area that contained patches of grassland.

The cats showed no significant difference in their stable carbon isotope ratios. That means they likely fed on the same prey and lived in the same habitat, but the posits that the species each fed on different sized prey.

The findings demonstrate the timelessness of predator-prey relationships.

“The three largest mammalian predators captured prey in different portions of the habitat, as do co-existing large predators today. So even though none of the species in this nine-million-year-old ecosystem are still alive today (some of their descendants are), we found evidence for similar ecological interactions as in modern ecosystems,” says Catherine Badgley, co-author of the new study and assistant professor of ecology and evolutionary biology.

READER COMMENTS (1) POST A COMMENT 
Posted by Quality Gourmet Food Distributors | Nov 17, 2012
I have never heard about Saber-toothed cats. What is the specialty of these cats? <a href="http://www.byrongourmetpies.com.au">Quality Gourmet Food Distributors</a>


Leave a comment

All fields are required.




email address will not be shown


Please enter the words you see below for anti-spam purposes:
NO SPAM

 

FACULTY SPOTLIGHT

U. Sean Vance, assistant professor of architecture, Taubman College of Architecture and Urban Planning, on what inspires him: “The quality of space. The ability of emptiness to move us and inspire us.”