How Citizen Science Led to The Discovery of Tree-Dwelling Toads

When you picture a scientist, you may picture someone  sitting in their office crunching numbers in a spreadsheet or in a lab moving small amounts of liquids from one tube to another. Often, however, scientists rely on the observations and enthusiasm of people outside of academia. Citizen science, the process of involving the public in scientific research, has led to several discoveries– and is evidence that you don’t need a PhD to contribute to science. 

Recently, two citizen science groups in the United Kingdom stumbled upon an unusual behavior in toads which may change our understanding of where toads live and how they interact with their ecosystem. 

A Brief History of Toad Living Habits 

Toads are stout-bodied amphibians with short legs, no claws, and no toe-pads, which would seemingly make it difficult to climb trees. Unlike their relative, the tree frog, toads are  considered ground-dwelling animals. Living on the ground allows the toads to be close to their food source, water, and they can seek shelter amid the leaf litter. 

Due to their abundance on the ground and lack of tree-climbing physical adaptations, researchers have not thoroughly explored the other environments where these toads may live. Enter: a coincidental sampling effort by two citizen science groups, which revealed a totally new habitat for terrestrial toads. 

The common toad in the habitat it is most frequently found in – the soil near water sources on the ground. Source: Creative Commons
Common toad” by erikpaterson is licensed under CC BY 2.0.
The Research Does Not Go As Expected

Many animal species live in trees. Birds build nests or live in tree cavities, while many bat species roost in trees. Even small mammals scurry up the tree trunk and seek refuge in the branches. In order to understand the diversity of animals that live in the trees, citizen science groups composed of volunteers from the local community scoured the canopies and recorded the animals that they saw. One group, the National Dormouse Monitoring Programme, surveyed for dormouse, a tree-loving rodent, while the Bat Tree Habitat Key looked for bats. Surprisingly, both groups found the common toad Bufo Bufo too. About 1% of sampled sites had amphibians living in the tree cavities, suggesting that this behavior is rare, but scientists were surprised to see them there at all. The toads were found in seven tree species, most frequently in the goat willow (Salix caprea). 

Goat willow forest. Toads were found living in cavities in this tree species. It was also the most common tree sampled by the two citizen science groups. Source: Creative Commons. 

GOC Willian & Weston Hills 117: Willian Arboretum” by Peter O’Connor aka anemoneprojectors is licensed under CC BY-SA 2.0.
Why do toads live in trees?

The survey that started as a search for bats and rodents led scientists to a new research question: what are the toads doing in the trees? Since this is a recent discovery, we don’t have the answer yet. However, researchers can hypothesize about the environmental conditions that may have lured the ground-dwelling toads up the trees. 

The toads were found in tree cavities and previously constructed nests by other tree dwelling creatures like birds and mammals. The researchers hypothesize that these structures provide the right conditions for the toads to live in. They are damp, isolated from predators, and provide an abundant insect population to prey on – which was also utilized by the birds that lived there before the toads moved in. 

This discovery of tree-dwelling toads is a growing field of research and both academic and citizen scientists are now studying these arboreal toads in depth to understand how they climbed the trees in the first place and if the toads ever return to the ground. As is often the case, new discoveries lead to more questions. 

Linking Academic and Citizen Science Leads to New Discoveries

Beyond the discovery of the new living habits of common toads, this study shows the value of collaborations between academic and citizen scientists. Including a diverse set of knowledge and lots of keen eyes looking for new discoveries help us understand the complex ecological interactions and lifestyles of the species living all around us – both on the ground and in the trees, or in the case of these toads, maybe both. And who knows, maybe you could help unearth a new scientific mystery. You can contact universities, museums, and outreach groups in your area to learn more about how to get involved in citizen science. 

Common toads are often found in the water since amphibians need to maintain moist skin. Source: Creative Commons

…and Relax. Bufo bufo. Common Toad (f)” by pete. #hwcp is licensed under CC BY 2.0.


Petrovan SO, Al-Fulaij N, Christie A, Andrews H (2022) Why link diverse citizen science surveys? Widespread arboreal habits of a terrestrial amphibian revealed by mammalian tree surveys in Britain. PLOS ONE 17(7): e0265156.

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Brianne Palmer

I am a PhD candidate at San Diego State University and the University of California, Davis studying how biological soil crusts respond and recover from fire. Most of my research is in coastal grasslands and sage scrub. We use DNA and field measurements to understand how cyanobacteria within biological soil crusts help ecosystems recover after low severity fires. I am also involved with local K-12 outreach within the Greater San Diego Metro Area.

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