Toads surprise scientists by climbing trees in UK forests — ScienceDaily

Volunteers surveying tree sleepers and bats have made the unexpected discovery of over fifty common toads in nests and cavities in trees at least 1.5 meters tall.

Until now, common frogs were considered terrestrial. The tallest frog in this study was found three meters up the tree, and scientists say there’s a chance the frogs will climb even higher.

This is the first time that amphibians’ tree-climbing potential has been investigated on a national scale.

The surprising discovery was made during a search for hazel dormice and bats as part of the National Dormition Monitoring Program and the Tree Bat Habitat Key Project.

The research was led by the University of Cambridge and Froglife and supported by the wildlife charity People’s Trust for Endangered Species (PTES). It was published today in PLUS ONE.

Dr Silviu Petrovan, Senior Research Fellow at the University of Cambridge and Trustee at Froglife and first author of the study, said: “This is a really exciting discovery and is important for our understanding of the ecology and conservation of common frogs – one of the most widespread and abundant European amphibians.”

He added: “We know that common toads prefer forests as a feeding and wintering habitat, but it appears that their relationship with trees is much more complex than previously thought.”

Common frogs are considered typical terrestrial amphibians, spending time both on land and in water during breeding. To date there are only a few documented sightings of common tree frogs in the UK.

Consequently, common toads and amphibians in the UK in general have never been surveyed in trees, unlike studies of bats and dormouses which specifically target this habitat. The study highlights the importance of data sharing between conservation organizations representing different species and shows that there is much to learn about UK wildlife – even for species thought to be well known.

Nida Al-Fulaij, Conservation Research Manager at PTES said: “We couldn’t believe what we found. We are used to finding woodpeckers and other small mammals in nest boxes, but we have not considered finding amphibians in them.’

Over 50 common toads were found during surveys of hazel dormice nests (located 1.5 m above the ground) and tree cavities commonly used by bats.

Many of the cavities were small or invisible from the ground, so it’s unclear how the frogs find them and how difficult it is for the frogs to climb certain trees.

Toads have not been found in boxes or tree holes with other species, but have been found using old nests made by dormice and even birds.

While 50 records is not a huge number, it is comparable to records of other animals known to regularly use trees – such as blue tits. This suggests that frogs spend more time in trees than previously thought. If this is true, it means that common toads can be found in up to one in every hundred trees in the UK in particularly favorable areas, such as near large bodies of water or lakes.

The discovery suggests that tree cavities may represent an even more important ecological feature than conservationists previously thought. It emphasizes the importance of protecting our remaining natural forest habitats, especially century-old trees with veteran features (such as hollows, cracks and other natural cavities) for all wildlife.

A study by Froglife in 2016 showed that common frogs have declined by an average of 68% over the past 30 years in the UK.

It is currently unknown why frogs climb trees and use nest boxes. Factors may include foraging, avoiding predators, or avoiding parasites such as the frog fly.

“Future targeted research will allow scientists to better understand the causes of this tree-climbing behavior in toads and how forest management should take it into account,” Petrovan said.

Froglife is urging members of the public to record any tree amphibian sightings on their Dragon Finder app or contact them directly.

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