Common Frog
The Common Frog is a semi-aquatic amphibian.
The adult Common Frog has a body length of 2.5 to 3.5 inches with females usually slightly larger than males. The back and flanks vary in colour from olive green to grey-brown, brown, olive brown, grey, yellowish and rufous. However, it can lighten and darken its skin to match its surroundings. The flanks, limbs and backs are covered with irregular dark blotches and they usually sport a chevron-shaped spot on the back of their neck and a dark spot behind the eye. Unlike other amphibians, the Common Frog generally lacks a mid-dorsal band but, when they have one, it is comparatively faint.
The Common Frogs is often confused with the Common Toad but the former can easily be distinguished as it has longer legs, hops and has a moist skin, whereas the latter crawls and has a dry warty skin.
The Common Frog can be found throughout much of Europe as far north as northern Scandinavia inside the Arctic Circle and as far east as the Urals, except for most of Iberia, southern Italy, and the southern Balkans. It is also found in Asia and east to Japan.
Outside the breeding season, the Common Frog lives a solitary life in damp places near ponds or marshes or in long grass. It is normally active for much of the year and only hibernates in the coldest months. Hibernation occurs in running waters, muddy burrows or in layers of decaying leaves and mud at the bottom of ponds or lakes primarily with a current. The oxygen uptake through the skin suffices to sustain the needs of the cold and motionless frogs during hibernation. In the most northern extremities of their range the Common Frog may be trapped under ice for up to 9 months of the year. In the UK, the Common Frog typically hibernates from late October to January. It will re-emerge as early as February if conditions are favourable and migrate to bodies of water such as garden ponds to spawn.
During the spring the Common Frog's pituitary gland is stimulated by changes in external factors, such as rainfall, day length and temperature, to produce hormones which, in turn, stimulate the production of sex cells: eggs in the females and sperm in the male. Breeding takes place in shallow, still, fresh water such as ponds. Spawning commences sometime between March and late June but usually in April over the main part of its range. The adults congregate in the ponds where the males compete for females.
The courtship ritual involves noisy vocalisations (croaking) by large "choirs" of males. The females are attracted to the males that produce the loudest and longest calls and enter the water where the males mill around and try to grasp them with their front legs. The successful male climbs on the back of the female and grasps her under the forelegs with his nuptial pads, in a position known as amplexus, and kicks away any other males that try to grasp her. He then stays attached in this position until she lays her eggs which he fertilises by spraying sperm over them as they are released from the female's cloaca. The courtship rituals are performed throughout the day and night but spawning typically takes place at night. Females lay between 1,000 and 2,000 eggs which float in large clusters near the surface of the water. After mating the pairs separate, the females will leave the water and the males will try to find another mate. Within 3 or 4 days all the females will have laid their eggs and left the water and the males disperse.
In common with other amphibia the rate of development of eggs and tadpoles is influenced by temperature, with those in ponds at higher temperatures developing faster than those at lower temperatures. Newly hatched tadpoles are mainly herbivorous and feed on algae, detritus, plants and some small invertebrates. They become fully carnivorous once their back legs develop and feed on small water animals or even other tadpoles when food is scarce.
Juveniles feed on invertebrates both on land and in water but their feeding habits change significantly throughout their lives and older frogs will eat only on land. Adults will feed on any invertebrate of a suitable size and catch their prey on their long, sticky tongues, although they do not feed at all during the short breeding season. Preferred foods include insects (especially flies), snails, slugs and worms.
The Common Frog is susceptible to a number of diseases and parasitic fungus infections which have been implicated in extinctions of amphibian species around the world. Loss of habitat and the effect of these diseases and infections have caused the decline of populations across Europe in recent years. In addition, tadpoles are eaten by fish, beetles, dragonfly larvae and birds. Adult frogs have many predators including a range of birds, mammals and reptiles. Some frogs are killed by domestic cats and large numbers are killed on the roads by motor vehicles.
Date: 8th April 2017
Location: Rainham Marshes RSPB reserve, Essex
The adult Common Frog has a body length of 2.5 to 3.5 inches with females usually slightly larger than males. The back and flanks vary in colour from olive green to grey-brown, brown, olive brown, grey, yellowish and rufous. However, it can lighten and darken its skin to match its surroundings. The flanks, limbs and backs are covered with irregular dark blotches and they usually sport a chevron-shaped spot on the back of their neck and a dark spot behind the eye. Unlike other amphibians, the Common Frog generally lacks a mid-dorsal band but, when they have one, it is comparatively faint.
The Common Frogs is often confused with the Common Toad but the former can easily be distinguished as it has longer legs, hops and has a moist skin, whereas the latter crawls and has a dry warty skin.
The Common Frog can be found throughout much of Europe as far north as northern Scandinavia inside the Arctic Circle and as far east as the Urals, except for most of Iberia, southern Italy, and the southern Balkans. It is also found in Asia and east to Japan.
Outside the breeding season, the Common Frog lives a solitary life in damp places near ponds or marshes or in long grass. It is normally active for much of the year and only hibernates in the coldest months. Hibernation occurs in running waters, muddy burrows or in layers of decaying leaves and mud at the bottom of ponds or lakes primarily with a current. The oxygen uptake through the skin suffices to sustain the needs of the cold and motionless frogs during hibernation. In the most northern extremities of their range the Common Frog may be trapped under ice for up to 9 months of the year. In the UK, the Common Frog typically hibernates from late October to January. It will re-emerge as early as February if conditions are favourable and migrate to bodies of water such as garden ponds to spawn.
During the spring the Common Frog's pituitary gland is stimulated by changes in external factors, such as rainfall, day length and temperature, to produce hormones which, in turn, stimulate the production of sex cells: eggs in the females and sperm in the male. Breeding takes place in shallow, still, fresh water such as ponds. Spawning commences sometime between March and late June but usually in April over the main part of its range. The adults congregate in the ponds where the males compete for females.
The courtship ritual involves noisy vocalisations (croaking) by large "choirs" of males. The females are attracted to the males that produce the loudest and longest calls and enter the water where the males mill around and try to grasp them with their front legs. The successful male climbs on the back of the female and grasps her under the forelegs with his nuptial pads, in a position known as amplexus, and kicks away any other males that try to grasp her. He then stays attached in this position until she lays her eggs which he fertilises by spraying sperm over them as they are released from the female's cloaca. The courtship rituals are performed throughout the day and night but spawning typically takes place at night. Females lay between 1,000 and 2,000 eggs which float in large clusters near the surface of the water. After mating the pairs separate, the females will leave the water and the males will try to find another mate. Within 3 or 4 days all the females will have laid their eggs and left the water and the males disperse.
In common with other amphibia the rate of development of eggs and tadpoles is influenced by temperature, with those in ponds at higher temperatures developing faster than those at lower temperatures. Newly hatched tadpoles are mainly herbivorous and feed on algae, detritus, plants and some small invertebrates. They become fully carnivorous once their back legs develop and feed on small water animals or even other tadpoles when food is scarce.
Juveniles feed on invertebrates both on land and in water but their feeding habits change significantly throughout their lives and older frogs will eat only on land. Adults will feed on any invertebrate of a suitable size and catch their prey on their long, sticky tongues, although they do not feed at all during the short breeding season. Preferred foods include insects (especially flies), snails, slugs and worms.
The Common Frog is susceptible to a number of diseases and parasitic fungus infections which have been implicated in extinctions of amphibian species around the world. Loss of habitat and the effect of these diseases and infections have caused the decline of populations across Europe in recent years. In addition, tadpoles are eaten by fish, beetles, dragonfly larvae and birds. Adult frogs have many predators including a range of birds, mammals and reptiles. Some frogs are killed by domestic cats and large numbers are killed on the roads by motor vehicles.
Date: 8th April 2017
Location: Rainham Marshes RSPB reserve, Essex
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Also in: Frogs and toads
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