Jon Cranfield

Is the common frog on the verge of dying out?

In Uncategorized on October 11, 2010 at 8:43 am

According to a Telegraph article (3rd October) it is feared that Ranavirus may have the potential to wipe out the common frog at least in localised areas.

Jeremy Briggs on his garden pond blog has pointed to the NARRS survey which revealed that over 50% of the ponds surveyed for amphibians recorded the common frog. I assume that this is highlighted to illustrate that frogs are not dying out.

The situation in garden ponds it seems from the limited surveys that I have been involved in over the last ten years seems to support the view that garden ponds are the stronghold for the common frog. Common frogs were recorded in over 80% of garden ponds in surveys carried out in 1996, 2000, 2001, 2002, 2003 & 2004. The focus in these surveys were urban and suburban areas and not in countryside ponds. A similar number of ponds were surveyed and a much higher occupancy was detected. Do we really know what the status of the common frog actually is in the UK?

Finding breeding frogs in countryside ponds is all very well but we have no idea of the population which is breeding in those ponds.

My old garden pond, in Eastleigh, had around 100 frogs breeding within It (based on peak spawn counts). This is somewhat surprising as the pond was only 1 metre in diameter. But the spawn count was over 45 and so for each clump corresponds to a female and for each female ther has to be a male and thus you get an estimate of approx 100 adults.

My old pond was designed as a wildlife pond and was not a standard garden pond. It was very good for frogs confirmed by the masses of froglets which emerged over the summer months.

Froglife are quoted that they have had reports of 30 to 40 dead frogs in garden ponds. In my pond that would have been 50% of my frog population. However in much larger ponds there tends to be many more frogs. An old employer of mine used to have a garden pond managed for frogs which had at least a population of 800!

A die off of around 40 frogs would be insignificant in these ‘super frog’ ponds.

There are many unreported ‘red leg’ cases and probably a similar number of frogs bouncing back after these die offs.

With an estimated 2 million garden ponds that is a very significant ‘stronghold’ but is probably one of the main sources of Ranavirus coming into the UK. So will frogs be killed off completely?

With the million ponds project the balance may be readdressed in clean water temporary ponds…

Posted with WordPress for BlackBerry.


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