Prehistoric Bear-Dogs and Saber-Tooth Cats Cohabitated
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. Image credit: Mauricio Antón
ANN ARBOR—The fossilized fangs of saber-toothed cats hold clues to
how the extinct mammals shared space and food with other large predators
9 million years ago.
Led by the University of Michigan 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.
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 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," said Soledad Domingo, a
postdoctoral fellow at the U-M Museum of Paleontology and the 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 said.
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 you 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 said.
"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 paper 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 coexisting large predators today. So even
though none of the species in this 9-million year old ecosystem are
still alive today (some of their descendants are), we found evidence for
similar ecological interactions as in modern ecosystems," said
Catherine Badgley, co-author of the new study and assistant professor of
ecology and evolutionary biology.
The paper is titled "Resource partitioning among top predators in the
Miocene food web." Other contributors are from the University of
California, Santa Cruz, and the Museo Nacional de Ciencias Naturales
CSIC in Madrid. The study was funded by the Spanish Ministry of Economy
and Competitiveness.
ARTICLE SOURCE: University of Michigan