Crateromys ballik: Paleontologists Find Fossils of Extinct Giant Cloud Rats in Philippines
Paleontologists have unearthed the 67,000-year-old fossilized remains from three extinct species of giant cloud rats in several caves on the Philippine island of Luzon.
Cloud rats are 18 living species of rodents with fluffy tails in the tribe Phloeomyini.
They can be found in the misty mountain forests of the Philippines.
They range in size from 18 g to 2.7 kg, typically live in trees, and eat leaves, buds and seeds.
Their evolutionary history in the region stretches back around 14 million years, when their ancestors first arrived in the Philippine archipelago from the Asian mainland.
The three newly-discovered species of cloud rats — Crateromys ballik, Carpomys dakal, and Batomys cagayanensis — are thought to be extinct.
Their fossils were found in Callao Cave, where a previously unknown species of human, Homo luzonensis was found in 2019, as well as smaller caves in the Cagayan province.
“Specimens of all three of the new species of fossil rodent were found in the same deep layer of the cave as the enigmatic Homo luzonensis indicating that they co-existed some 60,000 years ago,” said Professor Philip Piper, a researcher in the School of Archaeology and Anthropology at the Australian National University.
“Our records show they were able to adapt and survive profound climatic changes over millions of years, so the question is what might have caused their final extinction?”
The timing of the last recorded occurrence of two of the species might offer a clue — around 2,000 years ago or shortly after.
This is after the first arrival of agricultural societies and the introduction of animals like domestic dogs, pigs and macaque monkeys to the Philippines.
“That seems significant, because that is roughly the same time that pottery and Neolithic stone tools first appear in the archeological record, and when dogs, domestic pigs, and probably monkeys were introduced to the Philippines, probably from Borneo,” said Professor Armand Mijares, a researcher at the University of Philippines.
“While we can’t say for certain based on our current information, this implies that humans likely played some role in their extinction.”
Crateromys ballik and Carpomys dakal became extinct just a few thousand years ago.
They were giants among rodents, both weighing about a kilogram — big enough that it might have been worthwhile to hunt and eat them.
“We have had evidence of extinct large mammals on the Philippine island of Luzon for a long time, but there has been virtually no information about fossils of smaller-sized mammals,” said Dr. Janine Ochoa, a researcher at the University of the Philippines
“The reason is probably that research had focused on open-air sites where the large fossil mammal faunas were known to have been preserved, rather than the careful sieving of cave deposits that preserve a broader size-range of vertebrates including the teeth and bones of rodents.”
“Our previous studies have demonstrated that the Philippines has the greatest concentration of unique species of mammals of any country, most of which are small animals, less than half a pound, that live in the tropical forest,” said Dr. Larry Heaney, a researcher at Field Museum.
“These recently extinct fossil species not only show that biodiversity was even greater in the very recent past, but that the two that became extinct just a few thousand years ago were giants among rodents, both weighing more than two pounds.”
By comparing the fossils to the 18 living cloud rat species, the scientists have a decent idea of what Crateromys ballik, Carpomys dakal and Batomys cagayanensis would have looked like.
“The bigger ones would have looked almost like a woodchuck with a squirrel tail,” Dr. Heaney said.
“Cloud rats eat plants, and they’ve got great big pot bellies that allow them to ferment the plants that they eat, kind of like cows. They have big fluffy or furry tails. They’re really quite cute.”
The findings were published in the Journal of Mammalogy.
Janine Ochoa et al. Three new extinct species from the endemic Philippine cloud rat radiation (Rodentia, Muridae, Phloeomyini). Journal of Mammalogy, published online April 23, 2021; doi: 10.1093/jmammal/gyab023