Scientists puzzled by toads squatting in dormouse nests high in trees

Scientists hunting for dormice have been surprised to find toads sleeping in their nest boxes, high up in the trees.

A study has for the first time revealed the frequency with which the common toad nests and breeds in the trees.

These toads were found dwelling as high as 3 metres above ground in trees, with a record of 50 found living in dormouse nest boxes.

Researchers said this was unexpected because common toads, regarded as terrestrial amphibians, typically spend their time either on land or in water. Though they occupy a variety of habitats, from woodlands to wetlands, there have been very few sightings of the common toad up trees.

The breakthrough was made by researchers at Froglife and the University of Cambridge. Originally on the hunt for dormice and bats, volunteers were surprised to find toads residing in hollow tree cavities. They say the discovery highlights the importance to wildlife of protecting natural woodland habitats, especially ancient trees with features such as hollows, cracks and other natural cavities.

Nida Alfulaij, conservation research manager at the People’s Trust for Endangered Species charity, said: “We couldn’t believe what we found. We’re used to discovering woodland birds and other small mammals in the nest boxes but we hadn’t considered finding amphibians in them.”

Research conducted by Froglife in 2016 found that common toads have declined by 68% on average over the last 30 years in the UK. Mass migration during spring makes the common toad the vertebrate species most vulnerable to road mortality in Europe.

The discovery of arboreal behaviour in common toads suggests that tree cavities may be a much more critical ecological feature than conservationists originally thought. The reason the common toad is finding refuge in trees and nest boxes is unknown, but the researchers suggest they may be searching for food or hiding from predators and parasites.

Dr Silviu Petrovan, senior research associate at the University of Cambridge’s zoology department and author of the research published in the journal Plos One, said: “These findings are significant and very exciting for our understanding of the ecology and conservation of common toads, one of the most widespread and abundant European amphibians.”

“Further, targeted research will enable scientists to better understand the reasons for this behaviour and the impact on woodland management for common toads and other amphibians.”

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