Watching a mass of tiny black tadpoles in the dappled sunlight is one of life’s great pleasures. With frogspawn appearing from February, it won’t be long before hopefully these amazing wriggly creatures are covering ponds across Sussex.
The common frog is a widespread amphibian in Sussex, being found in a variety of damp habitats from urban gardens to wide open marshes. It is easy to identify, with smooth moist skin, long, stripy legs and a dark mask across the eyes. Although most people think of frogs as green, they can be hugely variable, with some individuals much more yellow, brown or even red.
Frogs are mostly active a night, when there are fewer predators and they won’t get dried out by the sun. However during the breeding season, hundreds of individuals can mass together in ponds. It can be tricky to tell the difference between the sexes. Females are generally a little larger, especially when full of eggs, and tend to have darker throats. Males often have a pale-bluish tint to their throat and also have swellings on their front index fingers, known as nuptial pads, which help them to grab onto females.
Mating occurs in spring and during mild years this can be as early as January, although February to April is more usual. Males croak to attract a female, before holding her in an embrace known as amplexus. Other males will mob pairs in amplexus attempting to dislodge the embracing competitor. Sometimes male frogs can be so enthusiastic that they accidently grab onto other males or even fish! Unfortunately the whole experience can be very tiring for female frogs and it is not uncommon for some of them to die of exhaustion after spawning.
Huge clumps of frogspawn can appear overnight, and depending on how sunny it is, can hatch out in just a few weeks. The tadpoles start out jet black, but as they get older they become a mottled greenish-grey with bronze speckles. It usually takes around three months for them to metamorphose into tiny froglets. At this stage they are only the size of a fingernail and must stay sheltered from the sun as they leave the pond.
Froglets will spend two years on land and only return to water once they are sexually mature. They are ambush predators, waiting for insects and other invertebrates to pass, before using their long sticky tongue to catch them. During winter, common frogs spend their time on land, often in log piles, compost heaps, stone walls or in the mud at the bottom of ponds.
Although they are still relatively common, frogs are thought to be declining in the UK due to loss of habitat, pollution and disease. The good news is, they love shallow garden ponds, so if you have the space, please add a wildlife-friendly pond to your garden.