An archeological mystery involving thousands of tiny bones has been solved and offers an unusual insight into Britain’s ancient wildlife. What was thought to be an amazing frog graveyard found in a ditch near Cambridge turned out to be the remains of a seasonal feeding ground used by birds of prey almost 1,700 years ago. After almost a decade of investigation, the researchers traced the remains to a group of hunting owls, showing how changes in the landscape in Roman Britain helped create the conditions for a giant amphibian feast.
A rare find outside Cambridge
According to reports in BBC and Phys Org, around 8,000 frog bones were unearthed between 2016 and 2018 during archeological investigations linked to the National Highways A14 Cambridge to Huntingdon improvement scheme. The remains were recovered from one ditch close to the site of an Iron Age roundhouse at Bar Hill, near Cambridge.The concentration of bones puzzled archeologists especially since evidence from the site suggested that the ditch filled in only a year. This meant that the accumulation could not be readily explained by a slow process over several generations.The discovery prompted further investigation and Bournemouth University researcher Dr Paul Clarkson asked Museum of London Archeology (MOLA) senior zooarchaeologist Dr Vicki Ewens to look closer at the remains. The study, published in the journal Environmental Archeology, shows how animal remains can offer important insights into both ecological conditions and human activity.
The mystery of the birds of prey
Clarkson compared the marks and damage on the ancient bones with evidence from previous research to identify birds of prey as the likely culprit. Short-eared owls and hen harriers seemed the best candidates. The results suggested that the frogs had been eaten and their bones deposited in the ditch.But this was only part of the investigation to find the predators. Researchers also had to determine why so many frogs congregated in one area in such a short period of time.The team came up with a new method that involved measuring the humeri, or upper arm bones, of the frogs. According to this analysis, Phys Org reports that most of the animals were young and died in the winter of their first year.The University of Vienna then conducted radiocarbon dating on the remains, and found them to be about 1,700 years old, placing the feeding activity in the Roman period.
How a changed landscape brought on the feast
The environment of the surroundings seems to have been important. During Roman times the fen wetlands in the valley were slowly receding, creating favorable breeding conditions for frogs, the BCC report states.Also large areas of woodland were cleared. Researchers studied evidence from snails, pollen and charcoal to determine how Iron Age forests were gradually replaced by open spaces for grazing livestock.The BBC says the loss of woodland cover meant there were fewer places for frogs to shelter, making them more vulnerable to predators hunting over grassland. Changing patterns of human activity including seasonal livestock movements and less continuous settlement in the area may also be reflected in the changing landscape.
Small bones tell a bigger story
The study not only identifies an ancient feeding ground, but also provides an unusual perspective on the relationship between wildlife and a changing landscape of the Roman era. The 8,000 bones that were once an archeological mystery have become evidence of how predators, prey and human land use created the environment centuries ago.Images Courtesy: istock and MOLA
