Frog spawn in tree mystery solved
Published 30/01/2013 | 11:20
Conservationists were left baffled when they discovered frog spawn up a tree, but the answer to the mystery lies in picky predators, not a new breed of tree frog.
Staff at Devon Wildlife Trust's working wetlands project made the surprise find of frog spawn six feet up on a tree trunk near Roadford Lake in north Devon, while working on land there.
Project manager Mark Elliott said: "Finding frog spawn at this time in winter is not that unusual, especially in the mild weather of the past week. But finding it up a tree was. It's not something I'd come across before. Common frogs lay their spawn in water and it's there that tadpoles develop, not in trees."
Mr Elliott sent a photo to Devon Biodiversity Records Centre, where staff who had seen the phenomenon before were able to give an explanation for the mystery.
According to experts, is not that unusual to discover frog spawn in trees, as animals and birds that eat frogs avoid the ovaries, because the spawn in them swell up massively in water.
The eggs in their jelly cases are less than 5mm across when laid, but expand to more than a centimetre across after a few hours, Ellie Knott from the records centre said.
She said: "This kind of finding is commonly known as 'star slime' - a lot of animals and birds eat frogs, but they don't eat their ovaries because the eggs or spawn contained in them expand massively when they come into contact with water.
"This expansion would be enough to give anyone stomach ache.
"So when birds and so on eat a frog they leave the ovaries behind, which then expand and burst when they get wet, leaving a clump of spawn."
She added: "In fact it is not that uncommon to find frog spawn in trees - buzzards and crows will often take frogs, retreat to a nearby perch and then eat their prey there, leaving the ovaries and the spawn behind after their meal."