Entombed within the 9 to 10 million year old rocks at Cerro de los Batallones in Spain’s Madrid Basin are at least nine different assemblages of large fossil mammals. Two of these deposits are rich in carnivore bones, and provide an interesting snapshot at how these apex predators coexisted.
The scientists published their findings in the journal Proceedings of the Royal Society B¹. Out of the 1,800 large mammal fossils recovered at one of these sites, 92% belong to 10 different species of carnivores. Small cats, skunks, civet-sized hyenas, and red panda relatives were found in large numbers. A pair of sabercats, the leopard-sized Promegantereon ogygia and the tiger-sized Machairodus aphanistus were found next to a bear dog (Magericyon anceps).
None of these Miocene carnivores have living descendants or even modern analogs, even though sabercats are often mistaken for tiger ancestors. The scientists drew upon geochemical clues drilled out from the teeth of the carnivores and their prey to see how these predators managed to coexist.
The researchers were after the stable isotope δ13C, which becomes incorporated into the teeth and bones of herbivores. Paleontologists use these values to estimate what kind of habitat a creature lived in. Carnivores preserve these traces as well. By comparing the trace isotopes in the three carnivores, alongside the herbivores they lived with, the scientists estimated which prey species were suitable candidates for each of the carnivores.
The sabercats seemed to prey on medium to small-sized herbivores, which frequented closed, wooded areas. The cats often dined on prehistoric pigs. The bear dog prowled more open spaces, and ate antelope and musk deer, which is known from partially digested remains supposedly left by a bear dog. Being of similar size, M. anceps and M. aphanistus probably avoided each other.
Sheer size shielded the mega-sized herbivores from direct predation by these predators, although the same species would have been vulnerable when young, elderly, or infirm.
- Domingo, M., et al., 2012. Proceedings of the Royal Society B. doi: 10.1098/rspb.2012.213