This illustration depicts how the region of Cerro de los Batallones in central Spain likely looked 9 million years ago. Researchers led by the University of Michigan 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 : Mauricio Antón/University of Michigan)

A new study sheds light on how extinct animals shared their food and space with large predators about nine million years ago.

A team of researchers led by the University of Michigan and the Museo Nacional de Ciencias Naturales in Spain studied the fossils of two saber-toothed cat species (the lion-sized Machairodus aphanistus and the smaller leopard-sized Promegantereon ogygia) and a bear dog species, that were unearthed in geological pits near Madrid, Spain.

All these species lived during the Miocene Period in a forested area that had patches of grassland. While the two cat species lived together in the woodland area, the bear dogs lived in an open area.

The research team carried out a stable carbon isotope analysis on the specimens collected. They used a dentist's drill with a diamond bit to sample teeth from 69 specimens, including 27 saber-toothed cats and bear dogs. The rest of the specimens belonged to plant-eaters.

Experts separated the carbon from the tooth enamel and measured the ratio of the more massive carbon 13 molecules to the less-massive carbon 12.

Both carbon 12 and 13 are present in the carbon dioxide that the plants take in during photosynthesis. Plants retain the isotopes in their fibers through different ways. When a herbivore eats a plant, the plant leaves an isotopic signature in the animal's bones and teeth. This isotope signature goes through the food chain and it can be found in the carnivorous animals that feed on these plant eaters.

Based on their study, experts revealed that the two species of cats hunted on horses and wild boars. Although the two cat species lived together, the smaller saber-toothed cats could have used tree cover to avoid facing the larger ones, said the researchers.

"The killing technique of these two saber-toothed cats is through a bite to the throat of the immobilized prey that produced a quick death due to the damage inflicted to blood vessels and trachea," study author Soledad Domingo, from University of Michigan, told Discovery News.

"These cats used their long, flattened upper canines to cut the throat of their prey in a head-depression movement in which the mandible served as an anchor," he said.

Domingo and his team also noticed that the cats did not show any difference in their stable carbon isotope ratios. This could mean that the cats fed on the same prey and lived in the same area.

The bear dog, which looked half bear and half dog, hunted on prey like antelopes. Despite the fact that these animals were living in the same geographical area, they were able to coexist by avoiding each other and apportioning their resources, said Domingo.

The forested area where the species lived is now called as Cerro de los Batallones, where Domingo has been excavating for the past eight years. There are nine sites in the region, two of which are ancient pits with plenty of bones belonging to meat-eating mammals.

The study concludes that the mammalian predators captured prey while coexisting with other predators in the same area. The authors point out that none of these species are alive today, except for some of their descendants. Similar co-existence and ecological interactions are also found in modern ecosystems, they said.

The findings of the study, "Resource partitioning among top predators in the Miocene food web," are published in the journal of the Proceedings of the Royal Society B.