A decade after researchers stumbled upon thousands of ancient frog bones buried at an Iron Age Roman-era site near Cambridge, England, scientists from Bournemouth University and the Museum of London Archaeology have solved the mystery, identifying hungry owls as the most likely culprits.
The team behind the discovery said their research not only solves a decade-long mystery but offers unique insights into the environment, animal behavior, and human movement during the Roman period, since human activities likely caused the bones to be buried in a short period.
Discovery Creates Ancient Frog Bones Mystery
According to a statement announcing the solution to the ancient frog bones mystery, the remains were first discovered ten years ago buried in a single ditch, “creating considerable media speculation about how and when these animals died and why so many were concentrated in one gully.”
An initial analysis determined that the over 8,000 bones, which were excavated between 2016 and 2018, were mostly from frogs. Still, the team noted, the origins of the ancient frog cemetery “were a genuine mystery,” leaving archaeologists to fill in the blanks.
When Dr Paul Clarkson at Bournemouth University saw reports of the ancient frog-bone mystery in the news, he reached out to Dr Vicki Ewens, MOLA’s Senior Zooarchaeologist, hoping to analyze the remains himself. While Dr. Ewens’ initial examination determined that bones were likely eaten by birds of prey, it didn’t explain why they were buried in a single ditch nearly 2,000 years ago. An analysis of the ancient ditch found it had likely been filled within a single year, deepening the mystery.
Animals Were Killed by Owls and Buried by Human Activity
After further examining the site and the ancient frog remains, the team radiocarbon-dated them. As suspected, the results showed the frogs had been slaughtered during the Roman Era, roughly 1,700 years ago.
When the researchers investigated the environmental conditions when the frogs were killed and buried, they noted that the Fen waters in the local valley were retreating. The team said this created the ideal conditions for the frogs to breed. The result was an abundance of food for local avian populations.
More research revealed that a predatory species of short-eared owls had hunted this region. The team also found more evidence in snails, pollen, and charcoal from the same site.
According to the team, this analysis revealed that large portions of the local woodlands were felled to create grazing land for animals during this time. When the Romans took over, the loss of woodland territory left the frogs with fewer safe places to hide from predators.
An analysis of the frog’s arm bones found that the remains were mostly from young frogs. The team said this suggests predators ate them during the first year of life, likely in winter.
Dr Paul Clarkson of Bournemouth University, who led the study, said the results showed that “this was the debris left by a community of predators.” Furthermore, the team found that human activities to create grazing lands resulted in the bones being covered over in a short period of time.
“The mystery of these frogs has been solved,” the researchers write, “a feast of frogs that were eaten and their bones left behind by a group of owls.”
So Many Theories, One Solution
When discussing the study’s findings, Dr. Clarkson said the bones offer insights into the lives of people and animals living near the Roman Fens. The research also said the solution to the ancient frog bones mystery lets researchers see what animals “were getting up to in the past, and what life was like for them.”
“We don’t often get an owl’s-eye view of what it was like in the past from archaeological sites,” the researcher said.
The researchers said the study offered insights into how people moved during the Roman Era. For example, the discovery of so many frog bones in one location suggests that owls’ prey was aided by tree removal for human activities. Dr. Clarkson also noted that the research highlights the value a single animal can offer, including insight into past environmental conditions and human activity.
When discussing the team’s personal reaction to solving a decade-long mystery, Dr. Ewens said they had “so many theories” as to why such a large collection of frog bones was recovered from this small feature.
“It’s been great to collaborate with Paul to finally answer this question,” the researcher added.
Christopher Plain has spent the last six years as Associate News Editor and Head Science Reporter at The Debrief. Follow and connect with him on X, learn about his novels at plainfiction.com, or email him at christopher@thedebrief.org.