The common toad is a rather rotund animal with short legs and an ungainly gait. It certainly doesn鈥檛 look like a good tree climber 鈥� yet citizen surveys suggest that common toads often climb trees to hide in hollows and nest boxes.
鈥淚t鈥檚 quite extraordinary,鈥� says at the University of Cambridge. 鈥淭he people who do surveying for bats were like, 鈥極h yeah, we do find toads from time to time鈥�. But nobody working with toads knows this.鈥�
The finding emerged from a dormouse monitoring run by in the UK. The nesting boxes are typically placed at least at a metre above the ground on tree trunks, so small animals can only get into them by climbing the trees.
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In 2016, a volunteer monitoring the nesting boxes found a toad in one of them and asked why it was there.
When Petrovan learned of this, he was intrigued. 鈥淗ow did the toad climb the tree? Why would it,鈥� he says.
He and his team couldn鈥檛 find any published reports of toads climbing trees, so they asked other volunteers with the PTES dormouse scheme if they had seen any amphibians. Sure enough, some had kept records of finding toads, even though they hadn鈥檛 been asked to.
Petrovan also looked at records of the occupants of tree hollows collected by another UK initiative called the project.
Altogether, his team has now found around 50 reports of amphibians in trees, almost all of them common toads (Bufo bufo). This might sound like a small number, says Petrovan, but these are tiny surveys. If the findings are representative, this behaviour may be very common.
For instance, just 1400 of the 3 billion trees in the UK were surveyed for the bat study. During these surveys in that research, blue tits (Cyanistes caeruleus) 鈥� a common UK bird 鈥� were found in tree cavities on 94 occasions, while toads were found on 19 occasions.
鈥淲hen you compare the records of toads with the records of blue tits in these cavities, they really do compare very well,鈥� says Petrovan. 鈥淎nd we know that blue tits really do go into these cavities.鈥�
The highest toad in the surveys had climbed 2.8 metres. But it is possible they go higher 鈥� Petrovan points out that the surveys are biased towards low tree cavities that people can reach easily.
Why toads climb trees to hide in cavities isn鈥檛 clear. It could be to avoid grass snakes or a parasitic insect called the toad fly (Lucila bufonivora) that lays its eggs on toads, Petrovan speculates.
Finding out more about this behaviour might help conserve common toads. Petrovan has previously shown that their numbers are .
Reference: bioRxiv,聽
