How a cave specialist and a paleontologist are piecing together Alberta’s post-glacial fossil record by exploring mountain caves. (OLD GOLD: published in Highline Magazine, Summer 2013)
Read the harrowing story behind the making of this diorama here.
Rappelling down a 30-metre vertical shaft into a cave in the Rocky Mountains was a first for paleontologist Dr. Chris Jass. “It was nerve-racking,” says Jass, who would have been more anxious had he not teamed up with Greg Horne, a cave specialist with Parks Canada. Jass gratefully describes Horne as a “safety first” kind of guy when, in 2009, the two were investigating a cave in eastern Jasper National Park.
Too intrigued by the cave’s suspected contents to let his fear get the better of him, Jass slowly lowered himself until he stood by Horne on the cave floor. As his eyes adjusted to the dim light, he was rewarded when the dusty beams of their headlamps revealed chunks of bones and fossil-filled rubble scattered on the cave floor. Jass had gotten what he had come for.
BEHIND THE SCENES
The story actually begins 12 years earlier when Horne first visited a similar cave, also in the eastern part of Jasper National Park. Colleagues at Alberta Fish and Wildlife suspected this cave was one of a few known little brown bat hibernacula in the province, and Horne was sent to investigate. Once inside, Horne quickly established the truth of it – little brown bats huddled in furry clumps along limestone walls, deep in hibernation to conserve energy in the winter months.
While confirmation of the bat hibernacula was important for regional bat conservation, Horne was more captivated by what generations of bats had left behind – a yellowed carpet of bat bones and skulls glowing in the light of his headlamp, accumulated over hundreds, if not thousands, of years.
And there weren’t just bat bones. As Horne carefully moved around the cave, he saw the skulls and jawbones of large carnivores, perhaps bear or wolverine. These animals had presumably fallen to their deaths at the steep entrance or “vertical trap” of the cave. Horne rightly suspected these bones could have significant paleontological importance. He logged the experience in his memory bank, and there it sat for over a decade.
In 2008, Jass, then a new paleontologist at the Royal Alberta Museum, contacted the Alberta Speleological Society, an organization promoting responsible, safe and environmentally sensitive cave exploration. Horne, an accomplished caver with experience in caves from New Zealand to Nahanni, had been a member for 18 years.
Jass was keen to connect with anyone who had sited bones in Alberta’s mountain caves. He had recently moved to Edmonton from Texas, after having spent his PhD identifying 150,000 year-old fossils from a cave in Nevada, and examining patterns of change over time in mammal fauna in the U.S. Great Basin between the Rockies and Sierra Nevada.
GETTING DOWN AND DIRTY
Now in Alberta, he wondered what bones and fossils preserved in caves could tell us about biological patterns after the last ice age. Did communities come back all at once, or as individual species? Were they the same species as before? Although fossil records existed for large mammals in parts of central Alberta, the post-glacial record in the Canadian Rocky Mountains was virtually non-existent.
Horne contacted Jass to let him know about the caves in Jasper National Park. He was keen to take Jass into the caves for a look, and a year later, after a significant rappel down a narrow shaft, Jass and Horne stood side-by-side in their first joint cave expedition.
They noted the sediment of the cave floor appeared to have been disturbed from previous human activity and possibly water drainage. Like a knife through a layer cake, some of this disturbance had exposed thousands of years of intact sediment strata. This piqued Jass’ interest because it meant the deposits in each layer would be the same age, providing enough material for radiocarbon dating. The two decided to return later for a proper dig; in the meantime, they made use of their research permit to collect a sample of the loose rubble for analysis in Jass’ Edmonton lab.
Under a microscope, Jass found tiny fragments of bones. One was the jawbone of a tiny shrew. He also found surprising numbers of tiny land snail shells, 1-2 mm in size, patterned with beautiful spirals Jass could only detect at magnification. “I didn’t expect so many of the snails, given the nature and structure of the cave,” says Jass, adding that we don’t have a great understanding of land snail fauna “because few people work on them, and they’re so small.” The fact that the entrance of the cave sits in a bowl-shaped depression may account for the large numbers. “Snails are likely washed in from the surrounding landscape,” Jass explains.
Jass and Horne later returned to the cave to conduct a “terminal dig,” in which fossils and bone were properly retrieved from the intact sediment layers. Jass identified the bones of salamanders, amphibians, snakes and even fish, perhaps discarded by birds of prey.
Charcoal from the same sediment layers provided a proxy date for the bones, indicating that most were between 1,700 and 2,700 years old. The quantity of charcoal indicated that a massive fire had once ripped through the area. “We’re talking a fire that would have incinerated part of the park,” says Horne.
The team was also surprised at the results of radiocarbon dating of a black bear pelvis found in the cave. At 6,000 years old, it was 3,000 years older than anything previously found in the rest of the cave.
These findings were a treasure trove, filling a major gap in the fossil record that had been previously missing from the post-glacial record in this area. Their discovery indicated that animals had returned to the mountains at least 6,000 years before present (BP).
The excitement grew when, along with Dave Critchley of the Northern Alberta Institute of Technology, the team visited a high elevation cave that has sub-zero temperatures year-round. There the team collected hardened woodrat dung that was eventually radiocarbon dated to 9,600 years BP, a time not long after the glaciers receded.
When he discovered the date, Jass was staggered. He double-checked the results. “That’s a fairly early date relative to what we currently know,” says Jass. “If woodrats were back, that probably means a lot of other rodents were back too. That gives us a minimum date for when small mammals reoccupied high elevations of the Canadian Rockies.”
These discoveries were just the beginning for Jass, who is still carefully sifting through more of the collected sediments. “It’s exciting because of the lack of data in the mountain area. I wouldn’t be surprised to find something older.”
These unraveled cave mysteries tell us that the suite of wildlife seen in Jasper National Park today is much the same as it has been for the past 6,000 years. Jass’ continued work may soon tell us which species re-emerged first, and when they arrived. Along with data from explorations in Rat’s Nest Cave near Canmore, these geological death traps are providing a broader view of post-glacial re-colonization in the Rockies. Although not always as exhilarating as dangling from ropes into caves, for Jass and Horne it’s exciting enough to solve these mysteries cave by cave, and bone by bone.
On May 13, 2009, paleontologist Chris Jass and Parks Canada Cave Specialist Greg Horne visited the bat hibernaculum where Horne first encountered the remains of centuries old carnivore bones. During their investigation, they discovered that the cave had been inspected by another visitor – one they wouldn’t know about until months later when the camera photos were collected.
11:11am – Jass and Horne descend into the vertical “trap” that acts as the cave opening.
12:07 – Within an hour of their departure, a black bear arrives to investigate. Notice that the bear smells the exact location on the tree where Jass had put his hand.
12:08pm – The bear creeps precariously close to the steep entrance of the cave. Says Horne, “Little does he know that his cousins or comrades are in the bottom of the cave as bones – [that date] back to 6,500 years ago – from doing the same thing: getting too curious, and falling and dying in there.”
12:08pm (later that minute) – The bear double checks on the tree smell.
12:09pm – Bear investigates motion-triggered camera.
16:43pm – Almost five hours later, Jass and Horne emerge, none the wiser. During our interview about the experience, Horne wonders what would have happened if the bear had fallen in. Would it have lodged in the opening, effectively blocking their way out? Or would the bear have died at the bottom, or maybe just have been hurt, leaving them in a cave with an injured bear?