Volunteers, who studied the sleepers and bats in the trees, unexpectedly discovered more than fifty common frogs in the nest boxes and hollows of trees at least 1.5 meters high.
Until now, common toads were considered terrestrial. The tallest frog in this study was found three meters up a tree – and scientists say there’s a chance the frogs can climb even higher.
This is the first time that the tree-climbing potential of amphibians has been investigated on a national scale.
The surprising discovery was made during a study to find dormouse and bats as part of the National Dormouse Monitoring Program and the Bat Tree Habitat Key project.
The research was carried out by the University of Cambridge and Froglife, with support from wildlife charity the People’s Trust for Endangered Species (PTES). It was published today in the journal PLANE ONE.
Dr Silviu Petrovan, Senior Research Fellow at the University of Cambridge and Trustee of Froglife and first author of the study, said: “This is a truly exciting discovery and important for our understanding of the ecology and conservation of common toads, one of the most widespread and abundant European amphibians.”
He added: “We know that common toads like forests as a place to forage and hibernate, but it seems that their relationship with trees is much more complex than we previously thought.”
The common toad is considered a typical terrestrial amphibian that spends time both on land and in water during breeding. To date, there have only been a few documented sightings of common tree frogs in the UK.
Thus, the common toads and amphibians of Great Britain in general have never been studied in trees, unlike studies of bats and dormice, which specifically target this habitat. The research highlights the importance of sharing data between conservation organizations representing different species and shows that there is much to be learned about wildlife in the UK – even species that are thought to be well known.
Nida Al-Fulaj, conservation research manager at PTES, said: “We couldn’t believe what we found. We’re used to finding forest birds and other small mammals in the nest boxes, but we didn’t expect to find amphibians in them.”
More than 50 common toads were found during research of dormouse nest boxes (located at a height of 1.5 m above the ground) and tree hollows, which are commonly used by bats.
Many of the cavities were small or not visible from the ground, so it is unclear how the toads find them and how difficult it is for the toads to climb certain trees.
Toads were not found in boxes or tree hollows with other species, but they were found in old nests of birds and even birds.
Although 50 records is a small number, it compares favorably with records of other animals that are known to use trees regularly – such as blue tits. This suggests that frogs spend more time in trees than previously thought. If this is true, it means that the common toad can be found on one in a hundred trees in the UK in particularly favorable areas, such as near large ponds or lakes.
The discovery suggests that tree cavities may be an even more important ecological feature than conservationists had thought. It emphasizes the importance of protecting our remaining natural forest habitats, especially ancient trees with old features (such as hollows, cracks and other natural cavities) for all wildlife.
Froglife research in 2016 found that common frogs have declined by an average of 68% in the UK over the past 30 years.
It is currently unknown why toads climb trees and use nesting boxes. Factors may include finding food, avoiding predators, or evading parasites such as the toad fly.
“Future targeted research will allow scientists to better understand why frogs climb trees and how this should be taken into account in forest management,” Petrovan said.
Froglife is urging members of the public to record any tree amphibian sightings on its Dragon Finder app or to contact them directly.