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Frogs

This section includes description of the common species.

The COMMON FROG -(Rana temporaria temporaria)(Rana = Latin for frog, temporaria = referring to the temporary or changeable lifestyle of a frog

Colour: Varies, upper part is yellow to red, may have dark spots, usually a dark patch over the ear.  Belly usually light and mottled, being grey in the male, and brownish/red in the female.

About: The common frog is widely distributed, though threatened due to pond pollution, collection and loss of habitat.  Found in vegetation, often in damp places. 

Breeding: Breeds in shallow water - even road ruts from the end of February to the end of April, but this can vary according to weather and location.  

Size: They reach a maximum length of 100mm.

The Edible Frog - (Rana esulenta)

Colour: Usually vivid green, though can be brown or blue; have black spots on their backs, yellow spots on their sides and a central yellow stripe along its back, and a white belly.

About: This frog was first introduced to the UK in 1837 and at other times since then.  It is thought to be confined to Surrey, Essex and Middlesex and is considered quite rare.

Breeding: From April to May, the female laying about 2,000 eggs. 

Size: Usually are a little larger than the common frog, but rarely over 120mm long.  It is thought edible frogs are a result of interbreeding between the pond frog Rana lessonae and the marsh frog Rana ridibunda.

THE MARSH FROG (Rana ridibunda)

Colour: Olive green to olive brown, some have pale stripe on back, has dark markings, the under surface is whitish grey.

About: Quite widespread in Britain, but its numbers are threatened by pollution and habitat loss.

Breeding: Breeds between April and May, the female laying up to 2,000 eggs.
 
FROG SPAWN


Usually the type of frogspawn that you will see in your or a local pond will be that of the common frog which tends to appear March to April and frequently.  

Though it is never advisable to take spawn from a pond, if you do, it is important that you make sure that you do not transport it anywhere else but your garden pond as there is an increasing risk of introducing disease or non-natural plant species into larger ponds and nature reserves. Some of these pond weeds flourish to an extent where they stifle the growth of the native plants.  Examples of plants responsible for polluting our waterways include: Parrot's-feather (Myriophyllum aquaticum), Australian Swamp Stonecrop (Crassula helmsii) and Water-fern (Azolla filiculoides), which can can be obtained from aquatic and garden centres and so may already be in your garden pond.

There was an article in the New Scientist Magazine ("Leave Well Alone", page 14, 2nd September 2000) about this very situation, though based in Australia, which suggests that 'amateur conservationists' are threatening the survival of the frogs they are trying to save

In nature, over 99% of spawn will not reach maturity, the majority are eaten by a variety of predators. If you do collect spawn follow the advice given below

(1) Be careful when collecting spawn, try not to damage surrounding spawn and avoid mating pairs of frogs/toads.  Use a net and collect whole clumps not breaking up established clumps.  Only take as much as you require, which is usually no more than 1 medium size clump.  Carry it in a large water filled container.

(2) Prepare a tank: Make sure that there is plenty of pondweed in with the tadpoles, preferably of a type that exists in the pond, if possible collect it from the same pond you collected the spawn.  The tadpoles will graze on the pondweed in their early days.  Make sure you de-chlorinate the water you put in the tank -this is easily done with a chemical from your local petshop.

(3) Gently place in the frogspawn, it will most likely sink to the bottom.

(4) Wait and watch.  The time it takes them to emerge is temperature dependant, so the spawn in your pond is likely to develop much later than those you keep in your tank in the house.

(5) The tadpoles will not be very active at first, clinging to the jelly or plant, they do not feed in the first few days as they have no real mouth at this stage, they obtain nourishment from their egg sac.

(6) After a further few days the eyes will open and the mouth develops and the tadpoles become more active and start swimming about somewhat.  The tadpoles tend to munch away at the pondweed, what they are actually eating is the layer of micro-algae attached to the larger pondweed.

(7) The tadpole obtains its oxygen using its feathery gills at the side of its 'head', which are quite visible.  As the tadpole develops away from this aquatic form, its external gills diminish and are replaced by internal ones.  These gills are similar to those of a fish and you can see small slits on the side of the tadpoles 'head'.

(8) Again, rate of development relies upon the temperature of the water.  Warmer weather/temperature increasing the rate of development.  But it may be a week to 5 before the front set of legs appear.  At this stage the tadpole is considered carnivorous, and will need a supply of finely chopped meat of some description, though only sufficient that will be completely eaten.

(9) It may be useful to transfer some pond water into you tank also, if you have a garden pond, the tadpoles will also eat the micro organisms/algae from this water, this is a more 'natural' food.

(10) The tail begins to shrink and from about 8 weeks on the gills begin to disappear and are developing lungs, the tadpoles begin coming to the surface to take gulps of air. Soon the tadpole turns slowly into a miniature frog with fully function legs!  Make sure you have a cover on your tank if it is inside, it is also a good idea to release the frogs at this stage unless you have a smaller tank to keep them in with a lower water level and rocks for them to perch on.

(11) It is not feasible to keep the frogs in captivity far beyond the stage they become froglets as they will not survive long in captivity, and are very capable of escaping with their powerful legs. 

There is a lot more information and advice about keeping tadpoles on the web. Future iterations of this page will include more links and children's activities.  













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