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The astonishing life cycle of frogs, from jelly-like bunches of eggs to ribbitting adulthood, is one of the wonderful stories of nature. It's a tale of tails, and how to lose them.
The seasonal transformation of these amphibians is one of the classic signs that spring has arrived, when at the edges of ponds and slow-moving streams, frogspawn appears and hatches into tadpoles. The tadpoles go on to develop legs and arms that young frogs (called froglets) use to leave their pools behind.
Read on to discover where and when you can find frogspawn, tadpoles and froglets each spring, and what to look for.
There are two species of frog native to the British Isles: the common frog (Rana temporaria) and the much rarer pool frog (Pelophylax lessonae).
The frogspawn of the common frog can be found just below the surface of ponds and other shallow, still water across the UK from around February onwards. But the timing can vary depending on where you are in the country and the weather conditions that year. By March, you can expect to find lots of frogspawn in ponds across the country. By laying large numbers of eggs, frogs increase the chances that some will survive to adulthood.
Ponds that are shady and have lots of reeds and other vegetation around them are particularly popular with breeding frogs. But frogs will even lay their spawn in temporary puddles.
When you do find frogspawn, as with all wildlife, it's better to enjoy it from a distance and not disturb it. You shouldn't move frogspawn from one pond to another, because conditions in the new pond may not be suitable and it can also spread diseases deadly to amphibians.
Frogspawn eggs bunch together in large clumps. This is how to tell the difference between frogspawn and toadspawn, which instead forms thin ribbons on underwater plants.
It takes around three weeks for young tadpoles to emerge. These tailed juveniles can be found swimming in ponds from around March.
Tadpoles are fully aquatic and have gills that they use to breathe underwater as they forage and feed. In younger tadpoles the gills are external and visible with a microscope or magnifying glass.
Young tadpoles begin by eating things like algae. As they grow, they go on to munch leaves, moss and sometimes even small insects.
Common frog tadpoles develop distinctive colouring which can help you identify them. They change from darker colours to a mottled golden brown as they age, distinguishing them from the black common toad tadpoles found in similar habitats.
As the months pass into April and May, you should be able to spot dramatic changes at the edges of your local pond as tadpoles slowly change into frogs. This process is called metamorphosis.
After about 16 weeks from when tadpoles hatch, the legs begin to form, followed by the arms. The tails gradually are absorbed into the body. Alongside this process, lungs form to allow the young frog to breathe above water.
A pond's particular environment can have a big impact on the speed at which tadpoles transform. For example, if there is a lot of food or the temperature is cold, tadpoles can delay the process of metamorphosis by several months. They can also increase the rate of change if this benefits them, for instance if they are sharing the pond with hungry predators such as fish.
Once their new bodies are developed, froglets leave the pond and begin a new semi-aquatic phase of their lives, splitting their time between land and water like all amphibians.
Their diet also changes, with the young frogs now feeding on a range of invertebrates including flies, slugs and snails. They still have a lot of growing to do. Common frogs reach up to 13 centimetres in length as adults (males are smaller than females) and live for around five to 10 years.
At around two to three years old, common frogs are ready to breed, restarting the life cycle.
Frogs are vulnerable to a number of predators and threats at each stage of their development.
Many animals eat frogspawn and tadpoles in the UK, including fish, beetles, newts, dragonfly larvae, rats and even foxes and hedgehogs.
Froglets and adult frogs are eaten by snakes, owls and other birds of prey, as well as mammals such as otters, badgers and weasels.
Unsuitable temperatures can also be a big risk to the development of frogspawn, which needs light and warmth. Spring frosts can be particularly bad news, as frogspawn will die if the temperature drops too low.
But some of the largest threats to frogs in the UK come from human activities. Find out about these threats and how you can help.
Although frogspawn might be the most obvious inhabitant of your local pond in spring, there's plenty more to life beneath the surface.
There are three kinds of newt species in the UK and, like frogs and toads, these creatures also breed in springtime.
Unlike frogs and toads, newts lay individual eggs and hide them away in vegetation, making them much more difficult to spot. Since newts eat tadpoles, you're likely to find fewer froglets in a pond where newts are in town. But newts also eat other pondlife such as midge larvae.
If you like a challenge and if it's safe to do so, why not follow the chorus of croaking and see if you can spot frogs, toads or newts in their various life stages in spring?
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