The common frog is a regular visitor to garden ponds across the country. In winter, they hibernate in pond mud or under log piles and in spring, they lay their eggs in big 'rafts' of spawn.

The life cycle of a frog is an extraordinary experience; they undergo an astonishing transformation, known as 'metamorphosis', as they grow from frogspawn to adult frogs.

This arrival of frogspawn is a classic sign that spring is on it’s way, so let’s explore the life cycle of a frog!

Frogspawn

It all starts with hundreds of tiny black eggs, which bunch together in large clumps. Each one is covered with a jelly-like casing, which keeps the eggs moist and also binds them together to protect the tiny tadpoles within. Freshly laid eggs are small and compact but as soon as they enter the pond they start soaking up water until they swell up to their full size. 

Frogs will often return to the pond where they born and will repeat this journey year after year. When mating, a male will attach himself to a female and they will remain attached for up to 24 hours while eggs are laid and fertilised. The males fertilise the eggs by spraying them with sperm. The female lays hundreds of eggs to increase the chances that more will survive to adulthood, as they are vulnerable to a number of predators, only around one in 50 eggs make it.

Frogspawn appears in ponds in early spring when the weather is just starting to get warmer and the days lighter. It is found just below the surface of shallow, still water, usually amongst dense vegetation to give the eggs some protection. You can tell the difference between toad spawn and frogspawn by the shape of the eggs, toad spawn is long pearl-like ribbons of eggs rather than large clumps that forms with frogspawn.

Tadpoles

The tiny black dots within the frogspawn are the earliest development of a young frog, known as tadpoles. The eggs change to an oval shape as the tadpole develops their tails. After 1-3 weeks, the tadpole emerges from the egg, they initially eat the yolk of their egg, but after a few days, they need to feed. Unlike their adult self, tadpoles only stay in water, feeding on plant material and nearby vegetation.

The legless, water-bound tadpoles slowly metamorphose into frogs over the next 14 weeks. The tadpole’s tails shrink away and skin grows over their gills. Amazingly, tadpoles are able to control the timing of their transformation. If they're living in a dangerous environment, they will metamorphose more quickly. On the other hand, if their pond has plenty of food and few predators, or if it is cold on land, tadpoles can delay their development by several months.

Fully-grown frog

Once the tadpole’s body has developed and formed lungs to allow them to breathe above water, they begin exploring the land, but stay close to their pond. Their diet starts to include larger items such as flies, slugs and snails. The transformation is now complete; our small tadpoles have become young froglets!

Frogs can take up to four years to develop to full maturity. An adult frog can reach up to 13cm in length and can vary in colour from green to brown, and even red or yellow. It has smooth skin, a dark 'mask' behind the eye, and long back legs, covered in dark bands. Frogs breed from between two and three years old, the males croak to attract the females and when they are ready to breed, the life cycle restarts!