Common Frog
Common Frog
Nature Notes - April 2011
Spring is one of the best times to see one of the UK’s few amphibians, the common frog.
Having spent the winter in hibernation under a pile of mud or decaying leaves where breathing through their skin enables then to survive, they rouse themselves to migrate back to ancestral ponds for breeding. These ponds may be ancient cattle drinking pools or just ordinary fish ponds in back gardens.
The frogs are often seen making their way across urban areas at this time; at my last house I frequently rescued them from the jaws of my cats. They seem to catch them but somehow find the taste unpalatable and hence they can be saved without any harm done.
Widespread and common across mainland Britain, their range stretches across Europe and eastwards to the far end of Asia.
Common frogs vary in size from about 6cms up to around 10cms with females being bigger than males. Smooth skinned, the colours vary from shades of brown to yellow and through olive green and onto grey with varying amounts of blotching. Like size, males tend to be different from females and are generally darker. Undersides are pale with varying degrees of speckling. Eyes are brown with horizontal black pupils.
The males are first to reach the breeding ponds and start their low croaking sound in an effort to attract a mate. Although active both day and night, they are more active at night and this is when their croaking can be best heard on quiet, still, moonlight nights. Once a male has successfully attracted a female, he will wrap his fore limbs around the female, an embrace known as “amplexus” and fertilise the eggs as they are released.
The familiar frogspawn is laid in shallow water and floats to the surface in clumps. It takes around a month for the tadpoles to emerge and they first survive on the spawn before turning to algae for food. The whole process of metamorphosis to frogs takes around 13 weeks; at 6 weeks the hind legs appear and at 9 weeks they have formed lungs and must come to the surface to breathe. Throughout this time and indeed once they have become tiny frogs, they are extremely vulnerable to predation and it is estimated that out of a 1,000 eggs only 2 will survive to become adults.
As adults, frogs eat any moving invertebrates such as worms, slugs, insects which they catch on their long sticky tongues. Unlike young frogs, adults feed entirely on land but curiously, do not eat at all during the breeding season.
During the dry spring last year, I visited a puddle by the Avon above Shipley Bridge that was full of tadpoles; as the puddle was in danger of drying out I daily ferried water in a bucket from the river to the puddle to keep them going and most seemed to develop and head away. Hopefully one or two of these will be back in another two years when they are sexually mature to breed in a more secure shallow body of water.
What to look for in April
April is an excellent month as spring is well under way. Look for returning birds and, if you have House Martins nests close by, note the date when they arrive back for comparison in future years. Hedgerows are full of flowers and Devon is no doubt one of the best counties in Britain for spectacular hedgerows. The first Cuckoos should be heard this month, with the third week being a typical arrival time. Slapton Ley and Dartmoor are good places.
First Published April 2011 By The Dart