26 February 2009

Myths exposed: “Too much spawn?”

Froglife’s enquiry service is in full flow now that the amphibian breeding season is beginning in many parts of the country. One of the most popular enquiries Froglife receives at this time of year is: “I have too much spawn...”

In some urban areas, numbers of adult Common frogs returning to ponds to breed can reach fifty or even over one hundred. Many people are surprised to hear that population fluctuations are a completely natural part of amphibian life. Sometimes even small ponds and water features are used by frogs to breed in such numbers.

Though amphibian numbers can be high in one year, in the years that follow numbers may drop sharply, as Lucy Benyon, Froglife’s Wildlife Information Officer, explains:

“We often hear reports of ‘too much spawn’ at this time of year. If you find this in your garden, there is usually no reason to be concerned or to necessarily intervene.” she says. “Frogs naturally produce lots of eggs because the odds of them surviving are so low.”

An often quoted statistic says that in a frogspawn blob of, say one thousand eggs, only three or four will make it from being eggs, through to tadpoles, through metamorphosis and finally to adulthood. Where competition between individual frogs is high, this number may be lower still.

“Many amphibians around the world are known for their fluctuating populations. When conditions are good their numbers can skyrocket – but then the competition between individuals can be so intense numbers will drop in following months and years.”

“Having lots of amphibians undoubtedly increase the wildlife value of your pond, your garden and your neighbourhood, since frogs after breeding will move back into the surrounding area to eat garden invertebrates like slugs, snails, woodlice and ants. Frogs will also end up being food for other wildlife like birds, dragonfly larvae, hedgehogs, newts and even grass snakes.”

“When frogs return to garden ponds in large numbers to breed, it should be a wildlife spectacle to cherish. It may not happen again for a number of years…” Froglife's Lucy Benyon finishes.

For more frequently asked questions about frogs in gardens visit: www.froglife.org/advice.htm

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