The Common Frog- Rana temporaria


Last time out in the Cooley’s we saw evidence of frog life with sightings of both adults and frogspawn. Find below information about their life cycle,  taken from the Irish Peatlands Conservation Council website.

Frog Life Cycle

When the adults emerge from hibernation they migrate to congregate at various breeding sites. They may travel up to half a mile to find a site where they gather in large numbers. The males always arrive first and strike up a chorus of loud croaking to attract females. Frogs do not have any elegant courtship rituals; the eager male simply grabs the nearest female as she arrives at the spawning site. Jumping onto the female’s back, the male wraps his fore limbs around her body and grips using nuptial pads, on the fore limbs – a position called amplexus.

Spawning itself can take place any time during amplexus and lasts only a few seconds. The female lays over 2,000 black eggs while the male releases sperm. The eggs are fertilised immediately and before their gelatinous capsules absorb water, swell and rise to the surface. After spawning the female usually leaves the pond, while the male often goes on to search for another mate.

Both male and female frogs return to the same pond year after year, probably recognising it from the smell of the water and algae.

Eggs & Frog Spawn: Each frog egg is 2-3mm in diameter and is enclosed in an envelope of jelly. When the egg is deposited in the water the jelly swells to a diameter of 8-10mm insulating the eggs from the water. The egg develops into a tadpole in 10-21 days (the higher the temperature the shorter the development time).

Tadpole: The tadpole digests the spawn jelly using a special secretion and hatches. Specific adhesive organs fasten the newly hatched tadpole to other spawn or plants in the pool. At this early stage tadpoles have no mouth, and until its mouth organs form it feeds on an internal yolk sac attached to the stomach. At approximately 2 days old the external gills, mouth and eyes are formed. At this stage it moves like a fish and begins to eat algae. At 12 days spiracles and internal gills are formed. At 5 weeks the hind legs are showing and the lungs are forming. It then has to swim to the surface of the water to gulp air. The tadpole has fleshy lips with rows of teeth for rasping away at water plants and by seven weeks it also eats insects and even other tadpoles.

Froglet: At 10 weeks the forelegs are growing. The hind legs are fully grown and the tail is reducing. At 14 weeks the tail is nearly fully absorbed. At this stage the froglets are usually starting to spend time on rocks or in nearby damp grass. Young frogs usually double in size by the following autumn and they reach sexual maturity in their third year. They can live for 7-8 years. Scarcity of food or severe cold may delay metamorphosis and overwintering tadpoles are not uncommon in northern countries.