Old Crow north of the Arctic Circle in the Yukon is not your typical small town. Here, temperatures reach a bone-chilling -36°C (-23.8°F) in winter and fossils literally erode from the bluffs and plonk near river banks.
The fossils come from all kinds of iconic Ice Age beasts: woolly mammoths, steppe bison, horses, and lions. Others come from not-so-typical creatures: flat-headed pecary, large-bodied camel, and now hyenas.
Paleontologists have confirmed the first known fossils of running hyenas (Chasmaporthetes) in the Arctic using two teeth dated between 1.4 million and 850,000 years old.
"To me, it is absolutely remarkable that they lived that far north," said study co-author Grant Zazula, Government of Yukon Paleontologist, to IFLScience.
The teeth were found in the lower Old Crow River – a remote region only accessible by boarding a plane to the local village, then traveling downstream by way of the river or by helicopter. The fossils belong to C. ossifragus, a specialized bone-cracking hunter-scavenger that "may have preyed on young mammoths, caribou, and horses," said Zazula.
"At this time, giant camels (Paracamelus) would have been one of the other large, common herbivores these hyenas would have encountered and preyed on or scavenged."
The region, although extremely cold, was never covered in glaciers because it was too dry. The Chasmaporthetes likely inhabited open ground and hunted with slender, cheetah-like limbs and razor-sharp teeth.
"These hyenas had to endure several months in the winter of near complete darkness, and incredibly cold conditions. Most climate reconstructions for the Ice Age suggest it was on average around 6°C colder than it is at present," said Zazula, whose research is published in Open Quaternary.
Researchers previously suspected that hyenas may have lived in Alaska or the Yukon at some point because they had to have crossed the Bering Land Bridge to travel from Asia to North America. "But, there was never any physical evidence for this until now," added Zazula.
The fossil teeth were initially discovered during expeditions to the Old Crow River in the 1970s. They were then stored in the Canadian Museum of Nature collections with around 50,000 other fossils until paleontologist Jack Tseng found decades-old notes on the specimens in the Swedish Museum of Natural History.
"The Yukon fossils represent one of the last records of this species. We estimate the North American species of Chasmaporthetes died out between 1 million and 500,000 years ago," said study author Tseng, from the Jacobs School of Medicine and Biomedical Sciences at UB, to IFLScience.
It is these proverbial needle-in-a-hay-stack fossils that are providing researchers with major advances in their knowledge of life during the Pleistocene and Holocene.
"There are several other species of Ice Age hyenas in Europe, Africa, and Asia, but the other species never braved their way across the Arctic into North America," added Zazula. "We know that Paleolithic people interacted with some Ice Age hyenas in Europe, because people painted pictures of them on cave walls."
Only four species of hyena remain today – three of the bone-crushing variety as well as an ant-eating aardwolf.
"Today the Arctic is a very fragile ecosystem and we have relatively very few large mammals," said Zazula. "This discovery of fossils that may be about 1 million years old helps us paint the picture of how mammal communities in the Arctic and in North America have changed significantly in a very short time period, in essentially a geological instant.
"These sort of discoveries kind of place stakes in the ground for our understanding of the potential of how quickly and significantly animal populations can change, move around, and die out when their populations are pressured by climate changes and competition with other animals."