Common frog

Common frog in wildlife pond Common frog in wildlife pond.

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Common Frogs (Rana temporaria)

Common frogs won’t spend all year in your pond, all they need is damp and shade so it is quite possible to find frogs in the grass and under logs and other hiding places quite a long way from the nearest body of water. That doesn’t mean you won’t see any frogs in your pond during the summer, in fact they are quite happy to sit on the edge of the pond sun bathing on warm sunny days. Frogs breed quite early in the year compared to other animals, as early as January in the south of England but a little later in the north. The males will find ponds and other bodies of water by following the smell of certain types of algae then once they have arrived will start to call the females with that familiar croaking sound. It would appear when watching that frogs don’t have any subtle courtship and it is just a free-for-all with any number of frogs hanging onto a female awaiting her to lay the eggs so they can try to fertilise them but research has shown otherwise. It has been discovered that when mating it is not the size of the male but the tone of the sound he emits which gives him priority over other males. It is the common rule however that the bigger the frog the deeper the tone of the croak. If then a large male frog has captured a female and is challenges by a small male the smaller of the two males will retreat. Therefore it seems on the face of it that the smaller attacker submitted to the larger defender because of its size. But in experiments a small male whose vocal chords had been temporarily silenced was placed on the back of a female. A speaker was put in place which when operated emitted the sound made by a larger frog. A large frog was then introduced which immediately tried to take occupation of the female. At this stage the speaker was switched on and emitted the deeper croaking sound at which the large frog immediately retreated leaving the smaller frog unchallenged.

The eggs are fertilised as they are laid and form a gelatinous mass of up to three thousand eggs. Frog spawn can appear as early as January. This has its dangers because if the temperature drops and the pond freezes over it will kill the eggs. Luckily not all frogs breed as early as this so those that breed later will survive. In the event of a mild spring and all the eggs surviving there will be a glut of tadpoles and small frogs which is good for other species as many other creatures feed on them. The eggs quickly develop and hatch after about two weeks depending on temperature, perhaps a little longer if the temperature is cold. When first hatched they have external gills and feed on algae. After eight weeks the two hind legs will have pushed through and they will have changed their dietary requirements from plant food to animal food and become cannibalistic devouring any of their weaker siblings. By the age of approximately twelve weeks they have developed their front legs and the tail has reduced in size to little more than a stump. Some however will remain neotenous and never form into froglets. There is some evidence that too many tadpoles in a small volume of water will result in fewer tadpoles turning into frogs so if this is the case it must be a rare example of predation being beneficial to the species.

They are now green and have in fact metamorphosized from tadpoles to frogs. They will now leave the water and live in long damp grass for the remainder of the year. Like adults they will hibernate and probably return to the pond where they were laid in the following year, however it will be three years before they are fully grown and able to reproduce.
There are three types of frogs in the UK: the Common frog (Rana temporaria), Marsh frog (Rana ridibunda) and Edible frog (Rana esculenta). The first, the Common frog is the only true British frog, the other two have been introduced. The one most likely to appear in your garden pond is our very own Common frog but you could be forgiven for thinking you have several species because the colouring of the Common frog varies dramatically from green and yellow stripes to yellow with black spots and even completely olive in colour.
The male can be distinguished from the female by a small lump on the first finger of its forefeet, this enlarges at mating time allowing him to cling firmly to a female. Frogs are a great asset to a garden so if you create a garden pond they will repay you by eating lots of slugs and snails which might damage your prized flowers.

If you have the slightest practical knowledge of frogs and toads it is not easy to mistake one from the other however if you have never encountered either it may be prudent to highlight a few salient points. Although toads like frogs do vary in colour it is only in shades of brown. They are usually lighter brown after shedding their skin and it slowly turns darker, underneath they are light grey to white. The most noticeable difference is the warty skin which is dry to the touch as opposed to the frog’s slippery feel. Another difference can be checked although slightly more hazardous, by carefully putting your little finger inside the mouth of the animal you can feel if there are any teeth in the upper jaw, frogs have teeth but toads don’t. I don’t think I would like to use this method of testing personally but I have never actually heard of anyone being savagely bitten by a frog.
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