The substance was found at the RSPB Ham Wall Nature reserve in Somerset, but a vet came forward to identify the blobs of jelly as linked to frogs.
Tony Whitehead, from the RSPB, said: "We've been delighted by the number of people that have contacted us about the mystery slime."
Devon vet Peter Green contacted the charity with a logical explanation for the slime.
Mr Whitehead explained: "At this time of year amphibians are spawning. The spawn is held in a substance, glycoprotein, which is stored in the female's body. If the animal is attacked by a predator it will drop its spawn and the 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 unfertilised, just the empty glycoprotein is dropped - which on contact with moist ground will swell and give a clear slime-like substance."
DID YOU KNOW? Frogs don't drink - they absorb water through their skin!