Description
This is a robust bodied toad with a triangular head, a pointed snout and short and thick limbs. Body color varies from dark green, yellow-brown to dark-brown depending on locality. Numerous round tubercles can be seen on the limbs, back, and lateral side of the trunk. Warts and parotoid glands above the tympanum secrete venom when attacked by a predator. In the breeding season, males and females have smoother skin, and the male's body color tends to become more yellowish. The tympanum is elliptical, and the eye-tympanum distance is about equal length to the long axis of tympanum. The fore-limb, with four fingers, is about half the length of the hind-limb; the third finger is the longest and the second is shortest. Hind-limb is nearly twice as long as the body; the fourth toe longest and the first toe shortest of all five toes. Webbing is poorly developed with deep incisions. (Maeda and Matsui 1990).

Compared to its previous subspecies Bufo formosus, B. praetextatus has smaller tympanums, otherwise they are morphologically very similar. However, protein composition analysis reveals genetic differentiation between the two. The snout-vent length ranges from 43-162 mm for B. formosus and 80-176 mm for B. praetextatus. Females' body length is usually larger than males. B. praetextatus living in warmer regions, on average, have greater snout-vent length.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Japan

View distribution map in BerkeleyMapper.

Bufo praetextatus is widely distributed in Japan. The habitat ranges from sea level to high mountain regions, and found in western Japan; Kyusyu, Shikoku, middle and south part of Honshu. (Maeda and Matsui 1990).

Life History, Abundance, Activity, and Special Behaviors
This species spends most of its adult life on ground, and migrate to water only for breeding. Breeding occurs between February and March in lowland areas when the temperature raises above 6 to 7 degrees. Breeding at one site last up to one week. Bufo praetextatus are thought to track the route to a breeding site using olfactory cues while mating behaviors are triggered by visual cues (Ishii et al 1995; Ishii et al 2000).

The breeding takes place in ponds, swamps, and puddles. Males usually outnumber females at the breeding site, often three to ten males for one female. Scrumble competitions between many males are observed during the breeding season. Long, string-like egg masses containing 1,500-14,000 eggs are laid on the bottoms of shallow water bodies, entangled among aquatic plats.

Bufo praetextatus feeds on a wide variety of arthropods and earthworms. According to Hirai's study (2000), diets of Bufo japonicus include ants, carotid and harpalid beetles, which are avoided by other predators because of the unpalatable chemical contents (formic acid and quinones, respectively.) Hirai (2000) suggests that the wide variety of diet may reduced food-related competition with other species and contributed to the wide distribution of Bufo praetextatus in Japan.

Bufo praetextatus buries itself under soils to hibernate when the temperature falls below 6 degrees.

Larva
Larvae have a completely dark body and reach 30-40mm upon maturation. Metamorphosis occurs in June. Sexual maturity takes about a year for males and two years for females.

Trends and Threats
Decrease of rice drainage of rice paddies during the winter time in recent years decreased the availablity of breeding sites for the toad in early spring. Rapid population declines have been observed in western Japan.

Relation to Humans
In traditional Japanese medicine, the toxic secretions from the parotoid glands of Bufo praetextatus are processed and used to apply topically on cuts and burns.

Possible reasons for amphibian decline

General habitat alteration and loss
Subtle changes to necessary specialized habitat

Comments
This species was featured in News of the Week January 22, 2024:

When toads invade an environment, they arrive armed with a chemical weapon: bufadienolides (BDs). Toads synthesize these potent cardiotoxins and store them in their lumpy skin as a defense against predators. Sawada et al. (2023) demonstrate for the first time that invasive toads can serve as a toxin source for a sequestering predator. The Tiger Keelback, Rhabdophis tigrinus, is a poisonous snake that eats toads and concentrates the consumed BDs in specialized glands that run along its back. R. tigrinus living on Sado island in Japan have been isolated from toad prey for 120,000 to 800,000 years, until the introduction of the Eastern Japanese Common Toad, Bufo formosus (formerly Bufo japonicus formosus) in 1966. The researchers detected bufadienolides in the gland extracts of more than half of the snakes sampled from toad-infested areas of Sado, but found no poison in the snakes sampled from parts of the island not yet invaded by toads. Intriguingly, the BD composition largely matched that of keelbacks which predate native Japanese Common Toad in other regions of Japan, and differed from keelbacks which eat a different toad species, Bufo praetextatus (formerly Bufo japonicus japonicus). This strengthens the case that B. formosus is indeed the source of BDs in Sado island keelbacks. The Tiger Keelback snakes from historically nontoxic populations exhibit different antipredator behaviors than historically poisonous ones, thus the re-toxicification of Sado island keelbacks may have interesting effects on fitness and the microevolution of behavior. While its frequency of occurrence is yet unclear, the phenomenon of invasive species as toxin sources is a novel paradigm for the study of chemical ecology and evolution in a changing world. (Kannon Pearson)

References

Hirai, T., and Matui, M. (2002). ''Feeding ecology of Bufo japonicus formosus from the montane region of Kyoto, Japan.'' Journal of Herpetology, 36(4), 719-723.

Ishii, S., Kaji, S., and Nakazawa, H. (2000). ''Oscillatory electric potential on the olfactory epithelium observed during the breeding migration period in the Japanese toad, Bufo japonicus.'' Zoological Science, 17(3), 293-300.

Ishii, S., Kubokawa, K., Kikuchi, M., and Nishio, H. (1995). ''Orientation of the toad, Bufo japonicus, toward the breeding pond.'' Zoological Science, 12(4), 475-84.

Maeda, N. and Matsui, M. (1990). Frogs and Toads of Japan, 2nd edition. Bun-Ichi Sogo Shuppan Co., Ltd., Tokyo, Japan.

Okada, Y. (1966). Fauna Japonica Anura. Tokyo Electrical Engineering College Press, Tokyo.

Species Account Citation: AmphibiaWeb 2024 Bufo praetextatus: Japanese Common Toad <https://amphibiaweb.org/species/204> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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