Frog Bones 1,700 Years Old Left by Birds of Prey in England's Fens

A Discovery That Revived a Dramatic Hypothesis

The site, a settlement in the Fens, the vast wetland area of eastern England, yielded a particularly dense pile of bones. More than 8,000 frog bones were extracted from a ditch associated with a roundhouse, a typical dwelling of Iron Age Britain.

Faced with such a concentration, some researchers suggested a frog cult practised between roughly 400 BCE and 43 CE. The hypothesis was appealing, but it rested on a missing piece of evidence: no cut marks were found on the bones, which makes human slaughter unlikely.

A Date That Places the Deposit in Context

The team led by Paul Clarkson first carried out radiocarbon dating of the bones. They date to around 1,700 years ago, a period when the Fenland waters were receding. This retreat of the flooded areas created a habitat favourable to frog breeding.

At the same time, grazing livestock had opened up the landscape, making the amphibians easier to spot and catch for predators of the grasslands.

Comparing Fractures to Identify the Predators

To identify those responsible, the researchers compared the damage on the frog bones with fracture patterns observed on animal bones, classified according to how the animal had died. This approach, which belongs to taphonomy, the study of the processes that affected remains after death, pointed to two species: the marsh owl and the hen harrier.

Measurements of the forelimb bones also showed that many of the frogs were less than a year old at the time of their death, a further indication of predation targeting young individuals.

A Feast of Birds of Prey, According to the Researchers

Paul Clarkson's conclusion is unambiguous: "The mystery of these frogs is solved: a feast of eaten frogs, whose bones were left behind by a group of owls." The case illustrates how the remains of small animals can be wrongly interpreted as ritual practices.

For archaeologists, the study is a reminder of the importance of archaeozoology, a discipline that makes it possible to distinguish natural accumulations linked to predators from deliberate deposits reflecting human action.

A Window onto Wetland Archaeology

The Fens are a particularly rich ground for research into ancient landscapes. Waterlogged soils often preserve organic materials rarely found elsewhere, making it possible to reconstruct entire ecosystems.

Readers interested in Iron Age and Bronze Age occupation in this region can consult published work on Fenland settlements, some of which reveal Bronze Age installations, and follow excavation reports from British sites in specialist journals.