In the northernmost reaches of Alaska, not far from the city of Barrow, lies an ancient site named Walakpa, which was home to Inuit people between 700 and 800 years ago. There, archaeologists have spent decades digging up the remains of buildings, tools, and a variety of local animals, including one very intriguing polar bear skull.

The narrow shape of this ancient polar bear skull caught researchers' attention. Image: Anne M. Jensen

Any polar bear skull is a sight to behold, but this one, discovered back in 2014, caught the eye of researchers. At about 40 cm (16 in) long, it's larger than most of the ancient bear skulls found in this region, and its slender shape brings to mind a legend passed down through generations of local hunters: the tale of the weasel bear.

The ancient residents of Walakpa belonged to the Iñupiat Birnirk culture, which appeared around 600CE, constructing homes across the Arctic. These resourceful people had few plants to depend upon, so nearly everything they needed – food, clothing, tools, building materials and more – they got from the body parts of local mammals, particularly marine creatures like seals and whales.

This ivory artefact from Walakpa is thought to be an early stage in the manufacturing of a thimble holder. Credit: Anne M. Jensen

"Hunters have a thorough knowledge of these animals and their behaviour, which is passed down from generation to generation," says Anne Jensen of the Ukpeagvik Inupiat Corporation Science Division, part of the Walakpa archaeological team.

Lurking in local lore are descriptions of an unusual type of polar bear: large, skinny and long-bodied. The local name for these creatures is tiriarnaq, meaning "weasel bear", in reference to their narrow frame. The accounts are striking enough that some have even wondered if these animals might represent a separate species or subspecies.

So, could the newly unearthed bear skull represent a weasel bear? The researchers aren't sure, but they do have plans to find out. According to Jensen, similar-looking skulls have been spotted at the University of Alaska Museum of the North by her colleague Raphaela Stimmelmayr from the North Slope Borough Department of Wildlife Management.

The team plans to extract DNA from the Walakpa skull, which is well-preserved enough to retain soft tissues, and compare this to modern polar bears. "If it does look different, the next step would be to get permission to sample the similar skulls in Museum of the North, both for dating and for DNA," Jensen says. If these "weasel bears" are indeed a different type of bear, their genetic data should show it.

The idea that the skull might represent a species unknown to science is definitely intriguing, but polar bear researcher Andrew Derocher of the University of Alberta suspects this isn't the case. "[T]here's nothing unusual about this bear when it comes to length," he says. The skull might be large compared to others dug up in this area, but Derocher points out that 40cm (16in) is about average for the skull length of living polar bears.

And when it comes to legends, Derocher has heard not just of the long, skinny tiriarnaq, but also of short, stocky animals sometimes called "badger bears". Polar bear body shape, he argues, can vary quite a bit: "There are long and thin and short and stocky bears. If you focus on the ends of the spectrum, you could easily come up with the weasel and badger bears." In his view, the Walakpa skull may simply have belonged to a lanky, but otherwise unexceptional, individual.

Time may tell us more about these animals, but time is not on the archaeologists' side. The new bear skull was found after intense erosion exposed new material at Walakpa, and this kind of landscape change is becoming more and more common all along Arctic coastlines. "Most of the sites along the Beaufort Sea coast of Alaska already have been severely damaged, if not obliterated," Jensen says.

The cause is familiar: a warming climate. In the cold winter months, coastal waters in Alaska are covered in sea ice, which blocks waves from reaching the shore. But as these waters warm, the ice persists for fewer months of the year, allowing more waves to chew into the land. What's more, the permafrost that holds the soil together thaws more in warmer years, leaving the ground more prone to erosion.

Excavators on site at Walakpa after the second storm of 2013. The next fall, a single storm eroded all this, and 30 metres farther inland. Image: Anne M. Jensen

"In the past, the usual procedure was to only excavate parts of a site," Jensen says. This meant portions of a site were left undisturbed for future decades, when improved technologies and methods might allow for more thorough excavation. "Obviously, with sites disappearing as rapidly as they are, that is no longer a good strategy," she adds.

The disappearing sea ice is bad news for bears too – weasel or not. "The main threat to polar bears is sea ice loss," Derocher says. "The sea ice is the primary habitat of polar bears and it's where they make their living."

While researchers continue to work to understand these animals, past and present, the world that supports them all is steadily melting away.


Image: foilistpeter/Flickr