Froglife News - 07 March 2008

Public advised to “stop the swap” of frogspawn this spring

As the milder weather sets in and frogs deposit millions of blobs of frogspawn in ponds around the country, a leading wildlife organisation is advising that the public do not donate their frogspawn to other gardeners.

The advice is being given by Froglife to help national efforts to stop the spread of invasive pond plants, animals and amphibian disease.

 “Sadly, moving frogspawn around often serves only to heighten the risk of moving around invasive plants and diseases that have potential to do real harm to frogs and other pond-inhabitants.” said Daniel Piec , Head of Conservation at Froglife. “If you want to do the best for wildlife, our advice is to leave frogspawn where it is and let nature do the rest.”

In the UK, the practice of ‘spawn-swapping’ goes back decades, and was one of the reasons that frogs have remained widespread in the UK while many other amphibian species are thought to have declined. However in recent years, as the global trade in pond plants and animals has taken off, so have appearances of a number of non-native ‘invasive’ species in the wild. Along with frogspawn can potentially come a number of harmful plants and diseases that can hitch a ride in the bucket.

Of particular concern is Australian Swamp Stonecrop Crassula helmsii, an extremely invasive aquatic plant from Australasia that forms dense carpets and stops sunlight reaching other plants. Other prime concerns are Parrot’s Feather, Floating Pennywort and Water Fern.

The spread of disease is a further concern to amphibians in the UK. A research paper published this month [1] suggests that a frog disease (a ‘ranavirus’ or frog virus), often mis-termed ‘red-leg’ which was first reported in the southeast of the UK in the late 1980’s, can be transmitted from adult frogs to their frogspawn. The disease kills thousands of frogs in the UK each year, though early research suggests that local populations can recover.

Instead of moving frogspawn artificially Froglife are promoting wildlife-friendly measures that allow frogs to move between ponds of their own accord. The charity advises against the use of concrete-based fencing around gardens, and suggests that gardeners add log piles to attract food for frogs, and provide hiding places like rockeries in which to attract frogs seeking places to lay dormant in winter.

“There are lots of ‘natural’ ways to get even the most urban garden ponds full of frogs – wildlife-friendly gardens and wildlife corridors are the key issue here.” said Froglife’s Lucy Benyon.

“Making gardens ‘frog-friendly’ in this way allows other native species a way into ponds too -whether it’s newts, pond-skaters or grass snakes- and these gardens form wildlife corridors that naturally encourage the movement of animals between ponds. This gets rid of the need to artificially introduce spawn, and lessens the risk of invasive species and diseases spreading further via accidental introduction.”

Froglife say that many enquirers to their Wildlife Information Service move frogspawn around because people fear they have too much in their ponds.

“If you think you’ve got too much spawn, think again. Survival of the fittest is what being a frog is all about. Of 2,000 eggs in a blob of frogspawn fewer than five frogs will ever make it back to the pond to breed as adults.” said Mr Piec.

For more information on frogs and frogspawn in gardens - see our advice sheet 'Frogs, Toads and Newts in Garden Ponds'.

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