The jelly-like substance was found in piles of about 10cm (4in) in diameter around the RSPB reserve.

Scientific speculation as to the nature of the jelly was varied.

One of the more favoured explanations is that it is a form of cyanobacteria called Nostoc or a certain kind of algae.

Others pointed out the sighting of a strange meteor like object over the reserve last week.

However the mystery has now been solved as an ordinary part of the British spring.

The RSPB was contacted by Peter Green a Devonshire vet who works with wildlife, who gave a particularly logical and simple explanation following his own researches.

Tony Whitehead, spokesperson for the RSPB , explained: “At this time of year amphibians are spawning. The spawn is held in a substance known as glycoprotein which is stored in the female’s body.

“If the animal is attacked by a predator – herons for instance are fond of the occasional frog – it will quite naturally drop its spawn and the associated glycoprotein. This is designed to swell on contact with water, which gives the gelatinous mass we are all familiar with in frog spawn. However, if it’s unfertilized, it is just the empty glycoprotein that is dropped – which on contact with moist ground will swell and give a clear, slime-like substance.

“While this is our favoured explanation for this appearance of slime, it’s also worth remembering that other things can give a similar appearance. Certain slime moulds can. So can the wonderfully named crystal brain fungus, but this only appears on wood. And certain algae, and blue-green algae can also appear as a clear slime.”

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