A group of archeologists working close to an Iron Age in the UK were baffled when they found over 8,000 bones of ancient frogs and toads. It’s unlike anything else that’s been discovered in the area, and the researchers aren’t sure why the bones were there but think it could be a sign of a prehistoric frog tragedy, more than a human ritual.

The bones, discovered by archaeologists from the Museum of London Archaeology (Mola) Headland Infrastructure, were found in a ditch at a site near Cambridge and are believed to be the remains of 350 amphibians. The team was doing archaeological digs in the area, focusing on a settlement from the Iron Age to the early Roman period (400BC-AD70).

The discovery is unique as no similar bones of amphibians from the region have been previously found. However, for the archeologists, it’s not just the find but also the quantity that is impressive. Vicki Ewens, a specialist in ancient animal bones at Mola, told The Cambridge Independent that having “so many bones from one ditch is extraordinary.”

The bones belong to the common frog (Rana temporaria) and common toad (Bufo bufo). Most were found on site were discovered in a 14-meter-long (46 feet) ditch on the western side of a roundhouse. Apart from the frog bones, the team also discovered artifacts and human remains across an area spanning 234 hectares.

Theories behind the finding

As this is prehistory and there is no written mention of this event, finding an explanation will be tricky. However, the group of archeologists already have their fair share of theories. First, they ruled out the frogs being eaten by the people living in the settlement. While there’s evidence of amphibian consumption in the UK, these specific bones have no cuts or burn marks.

The archeologists found evidence of charred grain near the site, which suggests that the inhabitant’s processed crops would attract pests such as beetles and aphids – which frogs are known to eat. This means the frogs could have been drawn to the area by the promise of food. Other potential explanations include a prehistoric frog tragedy.

Frogs are known to move in large numbers in spring as they search for breeding waters. They could have fallen into the ditch and become trapped, according to the researchers. The unusual death toll could have also been caused by winter hardship. The extreme cold could have killed the frogs as they fell victim to a very severe winter.

“This is a puzzling and unexpected find, which we are still trying to fully understand,” Ewens added, speaking with The Cambridge Independent. “This accumulation of frog remains may have been caused by a number of different factors, possibly interacting over a long period of time – we just aren’t sure yet what these were.”