This beautiful toad ranges from 48-120 mm snout-vent lenght. The following characteristics are used to describe the green toad: it has a diploid set of chromosomes 2n = 22; the parotoid glands behind the eyes are prominent; the pupil of the eye is horizontal; the tympanic membrane and male guttural resonator are present;the internal edge of the tarsus contians a longitudinal skin fold; the 3rd toe has a singular subarticular tubercle; the tip of 4th finger exceeds the 1st articulation of the 3rd finger; the dorsal skin is tuberculate, grayish or olive with green or olive spots and red or red-orange points onthe flanks. The belly is grayish. Male differs from the female by having nuptial pads on the first finger (in breeding season on the 1st, 2nd and 3rd fingers), smaller body size, and sometimes more greenish dorsal background coloration (grayish in females) during the breeding season.
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Albania, Austria, Belarus, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Estonia, France, Germany, Greece, Hungary, Italy, Kazakhstan, Latvia, Lithuania, Moldova, Republic of, Montenegro, Poland, Romania, Russian Federation, Serbia, Slovakia, Slovenia, Spain, Switzerland, Ukraine
The western margin of the range runs from the eastern and southern coasts of Sweden (ca. 59oN), then to Estonia, Germany (through some islands and the lands of Shlezwig-Holstein: east from the line Fehmarn - Oldenburg - Bad Segeberg - Hemburg; Lower Saxony, Northern Rhein-Westfalia, Rheinland-Pfalz and Baden-Wurtemberg), France, Southern Austria and Northern Italy. The toad is present on large Mediterranean islands (Corsica, Sardinia, Sicily, Malta etc.). The northern margin of the range starts from the southern Sweden, then runs through Latvia (surroundings of Riga City: 56o58'N, 24o05'E), south of Estonia, then through Russia eastwards approximately along the line Pskov Province - Yaroslavl Province - Ivanovo Province - Nizhegorodsk Province - Kirov Province - Udmurtia - south of Perm Province. Then the margin turns southeastwards in Chelyabinsk and Kurgan provinces, then through Northern and Eastern Kazakhstan. There, the northeastern localities are known from the Ishim River valley and the provinces of Tselinograd and Pavlodar. Then the margin runs southeastwards through Semipalatinsk and Eastern Kazakhstan provinces. The southeasternmost localities are known from Markakol Nature Reserve (48o26'N, 85o49'E) and Rakhmanovskie Klyuchi in the Western Altai. In the Russian part of the Altai Mountains, Green Toads were found in the Altai Region and in the Republic of Gornyi Altai, then probably to China (Xinjiang). To the south, the toads live to Middle Asia, Arabian Peninsula, Iran, Afghanistan and Pakistan. In many southern areas B. viridis is syntopic with other members of the group of green toads (e.g., B. danatensis), and its real distribution needs further exploration in the context of complex revision of this group.
Bufo viridis is one of the most polytopic amphibians of the Palearctic. It lives in the zones of forests, forest steppes, steppes, semi-deserts and deserts. It is more tolerant to dry conditions than many other amphibians. It inhabits both wet swampy areas as well as dry deserts of different types. In the forest zone, the species tends to live in open areas and bushlands, often far away from water bodies, whereas in the southern dry parts of the range it primarily inhabits moist sites such as oases, the shores of irrigation ditches and lakes. There it uses irrigation ditches and channels as corridors for dispersal. Spawning occurs in a diverse range of water bodies including ponds, swamps, lakes, stream- and river pools, reservoirs, ditches and puddles, as a rule not deeper than 50 cm. Both fresh and saline waters are used for spawning.
Life History, Abundance, Activity, and Special Behaviors
Bufo viridis is a common species throughout a large part of its distribution. It is generally rare at the north of its distribution, but in some places it forms dense populations in anthropogenic areas. This trend is very typical for green toads, and in some regions their abundance in anthropogenic habitats is much higher than in adjacent natural habitats. The use of burrows sometimes increases B. viridis density in the colonies of some burrowing rodents. In suitable habitats, its abundance reaches more than 100 individuals per 100 m2. The toadlet population density during metamorphosis reaches several dozens of individuals per 1 m2. In arid areas, the toad seems to be distributed more unevenly, forming dense populations in oases separated by wast dry areas unavailable to the toads.
Green toads are very heat-tolerant amphibians: the upper temperature limit appears to be near +40oC. They are also quite tolerant to desiccation (the death occurs when the body loses ca. 50% of its water). In dry areas, the toads regularly visit water bodies at night to rehydrate. Green Toad is active mainly in the twilight and at night and spends the daytime in hiding places. During reproduction, toads are active in daytime. Even terrestrial adults are often active on sunny days and in open areas. Daylight activity is known primarily from the southern dry part of the range and in the highlands. On hot days, the toads frequently stay in shallow water. On the other hand, migrations of long distances, up to 2-5 km from the breeding ponds are typical.
Hibernation occurs on land, but sometimes it occurs in water such as streams, ditches and wells. Toads hibernate singly or in groups. The timing of hibernation varies significantly through the range, in dependence on altitude and latitude. In southern parts of distribution, the hibernation often is absent, and the toads are active throughout the year. On the other hand, in southern deserts, aestivation supposedly occurs. Reproductive period is also quite variable, from February to July in different parts of the range. In the southern areas, the reproductive period is the longest (ca. 170 days), whereas the duration of development prior to metamorphosis is shortest (ca. 21-25 days).
Spawning occurs in a diverse range of water bodies including ponds, swamps, lakes, stream- and river pools, reservoirs, ditches and puddles, as a rule not deeper than 50 cm. Both fresh and saline waters are used for spawning.The Green Toad uses two mating strategies: active female choice by the competing males and active male choice by the females. Amplexus is pectoral. Assortative mating has been recorded. The clutch contains 2000-30000 eggs arranged in 1-2 rows. The spawn is deposited in two strings of 2-7 m length. Metamorphosis occurs from spring through the summer, in dependence on the latitude and altitude. Mass appearance of newly metamorphosed juveniles is typical for the Green Toad. In such cases pond shores may be covered with thousands of toadlets which disperse from the pond soon after their metamorphosis. Sometimes migrating toadlets form large groups moving as a large band. Maximum longevity is estimated at 7-10 years in different populations of the Caucasus.
Tadpoles consume detritus and algae and move towards the shore in daytime and to greater depths in the evening. Animals (Protozoa, Rotatoria, Microcrustacea) are consumed in smaller amounts. Newly metamorphosed toadlets prey upon Collembola, Coleoptera, Acarina and Diptera. Adults eat mainly crawling invertebrates, including spiders, beetles etc. Small amounts of aquatic invertebrates sometimes occur in stomachs of individuals caught in the spring along pond shores. However, the majority of toads do not feed during their breeding migrations. In similarity to other toad species, the Green Toad displays mirmecophagy. Ants compose a significant component of the adult but not juvenile food. Therefore, this peculiarity develops in the toad's postmetamorphic life and may relate to age changes in its foraging strategy.
The Green Toad composes an important component of food in many predatory vertebrates. Some snakes (e.g., Naja oxiana) prefer toads to frogs (Rana spp.).
Trends and Threats
Destruction of meadows, drying of wetlands, urbanization and recreation may lead to the decline of the Green Toad populations. On the other hand, destruction of forests may favor this species, which is adapted to open areas. In such areas the toad displays local dispersal, especially in the central and southern parts of its range. Deliberate introductions by people in some places (even far away from the main part of the range in Siberia) are known. In some places the Green Toad displays alternating increase and decrease in its abundance. For example, in Moscow Province the species was were rare in 19th Century, but to 1970s it became numerous. In 1980s the abundance has decreased significantly, and in 1990s the species has became so rare that it was included in the local Red Data Book. These changes may relate to multiyear fluctuations of climate.
Relation to Humans
As indicated above, many kinds of anthropogenic activity influence negatively the toad populations. On the other hand, B. viridis often occurs in anthropogenic landscapes and even prefers them habitats (fields, gardens, vineyards, parks etc.) over other. The toad is very common in many cities (especially in the south) where it finds suitable wet conditions in parks and fountains. The high potential for synanthropization allows the toad to disperse in some areas. Sometimes the toad occurs even in areas heavily polluted by industrial wastes, e.g. in the neighborhood of large industrial enterprises and scrap heaps. The toad also forms stable populations in some cities, especially in southern areas. The presence of suitable breeding pools is a necessary condition in such cases because adult toads readily settle near human houses, even in areas of multistoried buildings. The animals are concentrated in the evenings under electric lights in search of insects flying to the light.
Bufo viridis is the central member of the group of green toads widespread in thePalearctics. Subspecific differentiation of this species, as well as taxonomy of green toad group in general, needs thourough study.
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Written by Sergius L. Kuzmin (ipe51 AT yahoo.com), Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow
First submitted 1999-09-30
Edited by Vance Vredenburg; JG (fixing maps 7/25/01) (2001-07-24)
Species Account Citation: AmphibiaWeb 2001 Bufotes viridis: Green Toad <http://amphibiaweb.org/species/312> University of California, Berkeley, CA, USA. Accessed Oct 21, 2017.
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Citation: AmphibiaWeb. 2017. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Oct 2017.
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