•This suggests that toads spend more time in trees than was previously thought.
•Common toads are regarded as typical terrestrial amphibians, normally spending their time both on land and water.
Until now, common toads were thought to be terrestrial but volunteers made the unexpected discovery of over fifty common toads in nest boxes and tree cavities at least 1.5 metres high.
During the study, the most extreme example they found was a toad that had climbed three metres up a tree. In light of this, scientists say that there is a chance the toads might be climbing even higher.
This is the first time that the tree climbing potential of amphibians has been investigated on a national scale.
The discovery was made during a survey to search for hazel dormice and bats as part of the National Dormouse Monitoring Programme and the Bat Tree Habitat Key project.
The research was led by the University of Cambridge and Froglife and supported by wildlife charity People's Trust for Endangered Species (PTES).
It is published today in the journal PLOS ONE.
Dr Silviu Petrovan, a Senior Researcher at the University of Cambridge said, "This is a really exciting finding, and significant for our understanding of the ecology and conservation of common toads".
"We know common toads favour woodlands as foraging and wintering habitats, but it appears their association with trees is much more complex than we had previously thought."
Common toads are regarded as typical terrestrial amphibians, normally spending their time on land and in water during the breeding season.
To date there have only been a handful of documented sightings of common toads in trees in the UK.
Consequently, the presence of common toads and UK amphibians in trees has never been researched before.
Nida Al-Fulaij, the Conservation Research Manager at PTES said,"We couldn't believe what we found. We're used to discovering woodland birds and other small mammals in nest boxes but we hadn't considered finding amphibians in them".
Many of the cavities were small or not visible from the ground, so it is unclear how toads are finding them and how difficult it is for toads to climb particular trees.
However, toads were not found with other species but in old nests made by dormice or even birds.
This suggests that toads spend more time in trees than was previously thought.
The discovery shows how tree cavities might represent an even more important ecological feature than conservationists had realised.
It highlights the importance of protecting our remaining natural woodland habitats, especially ancient trees with hollows, cracks and other natural cavities.
It is not currently known why toads are climbing trees and using nest boxes but scientists have suggested factors could include searching for food, avoiding predators or evading parasites such as the toad fly.
"Future targeted research will enable scientists to better understand the reasons for this tree-climbing behaviour in toads, and how woodland management should take it into account," said Petrovan.