The Japanese common toad, Japanese warty toad or Japanese toad (''Bufo japonicus'') is a species of

toad Toad is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands. A distinction between frogs and toads is not made in scient ...

in the family

Bufonidae {{Cat main, Toad This category contains both species commonly called toads, and the true toads from the family Bufonidae {{Cat main, Toad This category Category, plural categories, may refer to: Philosophy and general uses *Categorization, cat ...

. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to Japan. Its natural

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

s are subarctic

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

s, temperate forests, temperate shrubland, swamps, freshwater

marsh A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found a ...

es, intermittent freshwater marshes, freshwater

spring Spring(s) may refer to: Common uses * Spring (season) Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of ...

arable land Arable land (from the la, arabilis, "able to be ploughed") is any land capable of being ploughed and used to grow crops.''Oxford English Dictionary'', "arable, ''adj''. and ''n.''" Oxford University Press (Oxford), 2013. Alternatively, for th ...

, rural gardens,

urban area An urban area, built-up area or urban agglomeration is a human settlement with a high population density and infrastructure of built environment. Urban areas are created through urbanization and are categorized by urban morphology as cities ...

pond A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Defining them to be less than in area, less than deep, and with less than 30% emergent vegetation helps in distinguishing their ecology from ...

s, and irrigated land. Amplexus is the mating behaviour involved in the Japanese common toad during the breeding season.

Description

The Japanese common toad can reach a snout–to–

vent Vent or vents may refer to: Science and technology Biology *Vent, the cloaca region of an animal * Vent DNA polymerase, a thermostable DNA polymerase Geology *Hydrothermal vent, a fissure in a planet's surface from which geothermally heated wate ...

length of up to about , with females being a little larger than males, and toads living in warmer habitats growing larger than those in colder places. The head has a pointed snout and is roughly triangular. The tympanum is elliptical and about as far behind the eye as its longest diameter. The body is robust and the stout forelimbs are about half as long as the hind limbs. The second finger on the hand is the shortest and the third the longest. On the hind foot, the first toe is the shortest and the fourth the longest. There is little webbing between the toes. The skin has small warty outgrowths and its colouring is variable, being greenish-brown, yellowish-brown or darker brown. It is often paler and smoother in the breeding season.

Distribution

The Japanese common toad is native to Japan and is present on the islands of

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island se ...

Hokkaido is Japan's second largest island and comprises the largest and northernmost prefecture, making up its own region. The Tsugaru Strait separates Hokkaidō from Honshu; the two islands are connected by the undersea railway Seikan Tunnel. The lar ...

, Kyushu and

Shikoku is the smallest of the four main islands of Japan. It is long and between wide. It has a population of 3.8 million (, 3.1%). It is south of Honshu and northeast of Kyushu. Shikoku's ancient names include ''Iyo-no-futana-shima'' (), '' ...

and the subspecies ''Bufo japonicus formosus'' has been introduced to the island of

Izu Ōshima is an inhabited volcanic island in the Izu archipelago in the Philippine Sea, off the coast of Honshu, Japan, east of the Izu Peninsula and southwest of Bōsō Peninsula. As with the other islands in the Izu Island group, Izu Ōshima for ...

and

. It is present in a wide variety of types of habitats including in lowland and mountainous areas.

Biology

The Japanese common toad lives mainly on land, feeding on earthworms and small arthropods including

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...

s and some species of

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

that are lamentable to other predators. It hibernates underground in the winter when the temperature falls below about . Breeding takes place in the spring when the toads congregate in shallow water bodies and long strings of eggs are laid and become tangled in underwater plants. The dark-coloured

tadpole A tadpole is the larval stage in the biological life cycle of an amphibian. Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial. Tadpoles have some fish-like features that may not be found ...

s grow to in length before emerging from the pond as juvenile toads in June.

Reproduction

The Japanese common toad is known for their intense male-male competition hence the type of breeding associated to this species is explosive breeding. The mating pattern of these toads is not conclusive but the major one is

polyandry Polyandry (; ) is a form of polygamy in which a woman takes two or more husbands at the same time. Polyandry is contrasted with polygyny, involving one male and two or more females. If a marriage involves a plural number of "husbands and wives ...

through

amplexus Amplexus (Latin "embrace") is a type of mating behavior exhibited by some externally fertilizing species (chiefly amphibians and horseshoe crabs) in which a male grasps a female with his front legs as part of the mating process, and at the same ...

. Preceding mating is courtship which is based on tactile and visual senses. The release of sperms from males is a result of the luteinizing hormone increasing in production and this whole process is induced by amplexus as the males clasp to the females.The size of the males is actually vital in deciding which competitor pairs with the female. The bigger males can always replace the smaller ones especially because amplexus is involved and the eggs need to be fertilized to suit the female's preferences. This is known as size-assortative mating which leads to male-biased operational sex ratio and in turn highly affects the male-male competition. Population density and operarional sex ratio are the two factors that contribute to how the males will compete for mating female partners. If the population of males in a specific breeding area is high, females are left with no other options but to practice polyandry. Migration to breeding ponds is important in ''Bufos japonicus'' and this process is tracked by the production levels of the oscillatory potential changes (OSC). OSC levels are highest during the breeding month when the toads have reached their breeding destinations. Other hormones like luteinizing hormone and follicle-stimulating hormone also spiral up when the species reach the breeding site. In conclusion, the four processes that take place during the breeding season are emerging from hibernation, migration, amplexing, and ovulation in females or spermiation in males.

Status

The Japanese common toad has a wide range and is tolerant of many different types of habitats including man-made ones. It is presumed to have a large total population and no significant decline in numbers has been observed so the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of nat ...

has assessed its conservation status as being of "

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

References