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Ten years after 8,000 frog bones were discovered in a single ditch, researchers from Bournemouth University and the Museum of London Archaeology (MOLA) have finally identified those responsible for this Roman frog graveyard. The bones were unearthed along the route of the A14 road improvement project between Cambridge and Huntingdon, between 2016 and 2018. According to work published in the journal Environmental Archaeology, birds of prey devoured the amphibians in a valley of the Fens, the former wetlands of eastern England.
A mystery born on a road construction site
The bones were discovered during preventive excavations carried out for the A14 road scheme, a programme managed by National Highways. The sheer scale of the accumulation, several thousand bones concentrated in a single structure, puzzled archaeologists, who explored several hypotheses over almost a decade.
It was after reading about the find in the press that Dr Paul Clarkson, of Bournemouth University, contacted Vicki Ewens, senior zooarchaeologist at MOLA. Their collaboration made it possible to combine fieldwork and laboratory approaches.
Birds of prey as the main suspects
By comparing the condition of the bones with earlier studies, Paul Clarkson found that the damage matched predation by birds of prey. The main suspects are the marsh owl and the hen harrier, two species that hunt over grasslands.
Zooarchaeology, the discipline that studies animal remains recovered from sites, thus makes it possible to trace the predators. The marks left on the bones act as a signature, much like tooth or beak marks.
Measuring the bones to date the season of death
It remained to explain how so many bones could accumulate in such a short time. The archaeological evidence shows that the ditch filled in within a single year. The Bournemouth team then measured the humeri, the arm bones, an innovative method that makes it possible to estimate the age of the individuals.
Most of the frogs turned out to be very young, having died during their first winter. Radiocarbon dating carried out by the University of Vienna places these remains at around 1,700 years old, in the Roman period.
A landscape in transformation
In Roman times, the waters of the Fens were receding in this valley, creating ideal conditions for frog breeding. The birds thus had an abundance of prey.
At the same time, the study of malacological, pollen and charcoal data revealed that wooded areas from the Iron Age had been gradually cleared for livestock grazing. The large open expanses deprived the amphibians of tree cover against hunters of the grasslands.
What these bones reveal about people and nature
According to Paul Clarkson, this discovery offers "an owl's eye view", a perspective on the past rarely accessible from archaeological sites alone. The researchers suppose that less populated landscapes favoured bird-of-prey hunting, with communities coming to the area seasonally to move their herds to new pastures.
For Vicki Ewens, even the smallest animal found on a site can shed light on past environmental conditions as well as human activity at the scale of the landscape. The full study, entitled "An Owl's Eye View: Human–Animal Entanglement at the Roman Fen Edge", is available in open access.
Frequently asked questions
Who ate the frogs of the Roman graveyard?
According to the study published in Environmental Archaeology, the frogs were devoured by birds of prey, probably marsh owls and hen harriers. The damage observed on the bones matches this type of predation. The researchers have thus solved the mystery of the ditch.
When did these frogs live?
The remains have been radiocarbon dated to around 1,700 years ago, placing them in the Roman period. They come from a ditch in the Fens valley, in eastern England. The dating was carried out by the University of Vienna.
Where was the frog graveyard discovered?
The bones were found between 2016 and 2018 along the route of the A14, between Cambridge and Huntingdon, as part of a road project. The excavations were carried out during preventive operations linked to the construction of the road.
Why so many frog bones in the same place?
The ditch filled in within a single year, and the frogs were mostly very young, having died during their first winter. The receding waters and the clearing of woodland created a habitat favourable to both amphibians and hunting birds of prey.
Sources
Original summary written with the help of artificial intelligence from the sources cited, checked automatically, then translated from the French original. Information and quotations belong to their authors. Read the French original.
