FROGS IN ASHWELLTHORPE – HUGE INCREASE IN NUMBERS, JANUARY TO MARCH 2016

As part of the Toadwatch patrols between 25 January and 7 April 2016, the volunteers also carried frogs to safety across The Street, Ashwellthorpe. An interesting phenomenon this year was the fact that we helped some 489 frogs across the road to and from the pond on Wood Farm land when the numbers between 2010 and last year ranged between 4 and 24 each year. The patrollers had, of course, noticed this abundance of frogs when, on some evenings 71, 66, 34 etc. frogs in some 45-minute sessions had kept them on their toes, but it was also noted by John Heaser, the initiator and co-ordinator of Norfolk Toadwatch. On 28 March, he commented “Has Ashwellthorpe had a plague of frogs? 24 last year and 431 this year! Where have they all come from?”

I replied that we’d all been wondering about this too as, on some evenings, two patrollers had found it almost impossible to gather all the frogs safely. I wondered whether a nearby small pond which was home to resident frogs had become congested and many moved to the next nearest stretch of water to breed. My understanding had been that frogs can live in small, shallower pieces of water, e.g. garden ponds, but toads like the deeper, still,  larger ponds as well as, of course, their native breeding pond. I also wondered whether our mass frog movement to the toads’ breeding pond  would interfere with the toads themselves. John’s understanding was that frogs, too, stay close to their breeding ponds and supposed that in Ashwellthorpe many of them are able to live in the Wood too, and that their numbers have increased. He also added re. the toads’ breeding pond on Wood Farm land that “hopefully the pond there is big enough for them to coexist with the toads”. He referred our e-mail correspondence to Dr Silviu Petrovan, Conservation Co-ordinator of the Froglife charity and Honorary Research Associate in the Faculty of Science at the University of Hull, and to Dr. Anne Edwards, Chair of the Wymondham Branch of Norfolk Wildlife Trust and Scientist of the John Innes Centre. Dr. Petrovan commented:

“Well, this is a really interesting question and one that does not have a simple answer. You’re both correct in your comments. Frogs can breed in very small bodies of water and sometimes stay close to them. Also, they often hibernate in the pond itself in good numbers. That means in general in ToR sites there are only frogs compared to toads. However……this is not always the case and, for instance, in other countries such as Switzerland, volunteers rescue similar toads and frog numbers overall as some sites have huge numbers of frogs (several thousand each) which cross the roads. Also we’ve been monitoring some tunnels in the UK where again, there are very large frog numbers crossing (under) the road. As such, it is basically a site by site situation. If thee are several available ponds, including very small ones, in good terrestrial habitat, frogs will stay close to the ponds, but in other situations (single large pond or lake or separation between aquatic and good terrestrial habitat) they can make substantial migrations towards a water body, just like toads do.

Also, there is no direct evidence of competition between frogs and toads either on land or in the pond. There is however, between common toads and natterjack toads in ponds.

Hope this helps”                                             Dr Silviu Petrovan

So, there we have an expert answer to our puzzle.

Jennifer Robbie                                                                      9 April 2016

 

 

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