True toads, harlequin frogs, and relatives

(Bufonidae)

Class Amphibia

Order Anura

Family Bufonidae

Thumbnail description
These are tiny to very large, generally warty or dry-skinned frogs, with usually unspecialized digital tips; most have parotoid glands

Size
0.6–9.8 in (15–250 mm)

Number of genera, species
33 genera; 344 species

Habitat
Deserts, savanna, dry and humid forests, from sea level to 16,404 ft (5,000 m)

Conservation status
Critically Endangered: 1 species; Endangered: 6 species; Vulnerable: 6 species; Lower Risk/Near Threatened: 2 species; Data Deficient: 3 species

Distribution
Worldwide, except for Madagascar, Australia (introduced), and New Guinea; bufonids just barely cross Wallace's Line to the east, and are present on the Indonesian island of Sulawesi

Evolution and systematics

Bufonidae currently contains 33 genera. Subfamily names have been proposed, but these were based on geographic distribution rather than evolutionary relationships and have not been widely accepted.

Scientists have not determined which are the closest relatives of Bufonidae. Although many data from DNA sequences have been accumulated recently, no other group of frogs has emerged as a close relative to Bufonidae. Although not known with certainty, South America is generally believed to be the continent of origin for the group.

Bufo is known as far back as the Oligocene (Whitneyan) of North America, the Miocene of Europe, western Asia, and North Africa, and questionably from the Middle Paleocene (with certainty from the Miocene) of South America.

Evolutionary novelties that unite the species of Bufonidae include the presence of Bidder's organ; a unique pattern of insertion of the rectractor muscle of the tongue (hyoglossus); the loss of the posterior constrictor muscles of the larynx; the absence of teeth; and the presence of the "otic element," an independent bone in the temporal region that fuses indistinguishably to the posterior arm of the squamosal bone.

Physical characteristics

The term toad is usually applied to frogs in the family Bufonidae. Sometimes "toad" is used for any frog that is rough-skinned, regardless of its evolutionary relationships. More often, toad is used to describe any member of the family Bufonidae. English is not the only language to recognize frogs and toads; the distinction is made in languages as diverse as French, German, Quechua, and Bahasa Indonesia.

Toads in the family Bufonidae are relatively diverse in their appearance. Yet all of them share certain structural characteristics that unite them into this taxon. Most frogs have teeth on the upper jaws, but all bufonids lack them. At the turn of the twentieth century, the presence or absence of teeth was considered to be a significant character for classification, and several species that herpetologists now know are unrelated were grouped into Bufonidae simply because they lacked teeth. Although several other groups of frogs have independently lost teeth, the absence of teeth in bufonids remains a diagnostic feature of the group.

Only the Bufonidae among frogs have a Bidder's organ. In amphibians, the testis and ovary develop from an undifferentiated mass of gonadal tissue. During larval development, the gonadal tissues of future males secrete testosterone, which causes the animal to develop as a male. In the absence of testosterone production, the animal will become a female. In other words, being female is the default sex. The organ of Bidder is a bit of gonadal tissue that apparently retains its female attributes in male toads, which also develop normal testes. If the testes of adult toads are removed surgically, Bidder's organ will transform into a functional ovary. Thus it seems that the presence of a functional testis, which produces male hormones, suppresses the development of the ovarian tissue of the bidder's organ. It is not known whether Bidder's organ has an adaptive or functional role in the natural life of toads.

Bufonids are basically hoppers and walkers, never leapers. The joint between the hip bones (pelvic girdle) and vertebral column (at the sacrum) is modified such that the range of motion is not in the longitudinal vertical plane, as in leapers such as Rana, but rather movement is from side to side. Also, several genera of bufonids apparently have evolved skeletal modifications

that perhaps reflect the reduced locomotor abilities of these toads. They have seven or fewer vertebrae (rather than eight as in most frogs). The coccyx is fused to the sacrum, rather than having a flexible joint. The left and right halves of the shoulder girdle are fused to each other, rather than having a flexible joint at midline. The number of bones in the hands and feet is reduced; the lengths of the fingers and toes are correspondingly shorter; and the hands and feet look more like a mitten rather than a glove (the name Atelopus means "incomplete foot"). All of these modifications suggest a reduced ability to jump. In fact, this is true. But also, these toads are all rather small, and the skeletal modifications might also result from a smaller size.

Skin glands are present in almost all amphibians and are generally widely distributed throughout the skin as small structures that are not obvious. In contrast, the parotoid gland consists of closely spaced skin glands concentrated into a prominent organ behind the ear. Within bufonids, one can distinguish two groups, those with parotoid glands and those without. Parotoid glands are found in all species of Bufo, as well as members of several of the non-Bufo genera. However, several non-Bufo genera lack parotoid glands. In some species the glands are difficult to distinguish without a close examination of the skin in cross section. When disturbed, the toad can discharge a milky venom from the glands, sometimes through the air. The secretions of large toads have been known to kill predators such as dogs.

Distribution

The genus Bufo has a world-wide distribution, with radiations in North America, Central America, South America, the West Indies, Africa (but not Madagascar), Europe, and all of Asia including Japan, the Philippines, Southeast Asia, and Sulawesi east of Wallace's Line.

The non-Bufo genera in the Neotropics include Crepidophryne and Atelophryniscus, which are endemic to Central America; Atelopus in Central and South America; and Andinophryne, Atelopus, Dendrophryniscus, Frostius, Melanophryniscus, Metaphryniscus, Osornophryne, Oreophrynella, Truebella, and Rhamphophryne in South America. The other genera endemic to Africa are Altiphrynoides, Capensibufo, Didynamipus, Laurentophryne, Mertensophryne, Nectophrynoides, Nectophryne, Nimbaphrynoides, Schismaderma, Spinophrynoides, Stephopaedes, Werneria, and Wolterstorffina. Some genera are found in Southeast Asia: Ansonia, Leptophryne, Pedostibes, Pelophryne, and Pseudobufo. Genera endemic to the Indian subcontinent include Adenomus and Bufoides.

Habitat

It is difficult to make general statements for a group with as many species and with as broad a geographic range as Bufonidae. Species may be found in near-desert to primary tropical rain-forest habitats, from sea level to 16,400 ft (5,000 m) in treeless alpine environments. The genus Bufo occupies the greatest range of latitudes and altitudes of any frog. Most bufonids would be termed terrestrial; very few are fully aquatic or arboreal.

Behavior

Behavior in this diverse group of toads varies. Very little is known about some species, while others are more well-studied. Atelopus varius is known to have exceptional homing ability.

Feeding ecology and diet

Like most frogs, bufonids feed mainly on a diet of arthropods. Ants form a large part of the diet in tropical areas. Despite their size, large toads such as Bufo marinus are not decidedly carnivorous, although they are capable of eating small mammals such as mice.

Reproductive biology

The mating call of most species is a trilled call emitted at a rather steady pitch, rather than an untrilled or pure tone that might rise or drop in pitch. Most bufonids lay numerous, small pigmented eggs that are enclosed single file in strings of jelly, rather than in a discoid or globular egg mass. These egg masses are usually laid in temporary ponds rather than large bodies of water or streams. Typically, the eggs develop quickly, with tiny tadpoles hatching out in large numbers. Most of these die, and the few that make it through metamorphosis do so as very tiny toadlets, regardless of the ultimate size of the adult. Even Bufo marinus has small toadlets; therefore the total weight increase over the life of the animal may be several orders of magnitude. Tiny toadlets are notoriously difficult to identify to the exact species. A few species of bufonids deviate from this general pattern and are presumed to have direct development, because the eggs observed in dissected specimens are large, few in number, and not pigmented. Few toads are known to exhibit parental care.

Many species of toads are known to hybridize in nature, and hybrids have been produced in the laboratory between species that are very distantly related, even from different continents.

Conservation status

The IUCN lists 1 species as Critically Endangered (Bufo periglenes), 6 as Endangered, 6 as Vulnerable, 2 as Lower Risk/Near Threatened, and 3 as Data Deficient. Although many species are not threatened and some are so common in human settlements as to be considered pests, several species appear to have suffered dramatic and mysterious population declines since the 1980s, along with many other amphibians.

Significance to humans

Because of their ubiquity, toads have been the subject of myth and lore.

Species accounts

List of Species

Malcolm's Ethiopian toad

Altiphrynoides malcolmi

taxonomy

Nectophrynoides malcolmi Grandison, 1978, 3.7–4.97 mi (6–8 km) south of Goba, Balé Province, Ethiopia. This species was formerly included in Nectophrynoides, a group of montane toads with specialized, but variable, modes of development.

other common names

None known.

physical characteristics

Adult males are 0.59–0.75 in (15–19 mm) and females 0.9–1.1 in (23–28 mm) in snout-vent length. The parotoid glands are very small, if present at all, and cranial crests are absent.

distribution

Balé Mountains, Ethiopia.

habitat

These toads are inhabitants of high mountains, at 10,500–13,100 ft (3,200–4,000 m). The normal ambient temperature in which the larvae are known to develop is 41°F (5°C).

behavior

Nothing is known except the reproductive behavior.

feeding ecology and diet

Nothing is known.

reproductive biology

Fertilization is internal in these toads. During mating, the male grasps the female just in front of the hind limbs (inguinal amplexus), but in contrast to the usual positions, amplexus occurs belly to belly, rather than with the male behind the female. The eggs are retained until the early neurula stage, when the embryo is beginning to develop a spinal chord. Then the eggs are laid and continue their development in the egg capsule, without active feeding. The embryos lack the mouth parts needed to feed, and they also have a short gut, indicating that it does not function in digestion. Thus, the embryo derives all of its nutrition from the yolk. Females have eggs that are huge relative to the body; the average clutch size is 18 eggs, with an egg diameter of 0.1 in (2.73 mm). The terrestrial egg clutches are thought to be communal, laid by as many as 20 females that are attracted by the chorus of calling males.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Long-fingered slender toad

Ansonia longidigita

taxonomy

Ansonia longidigita Inger, 1960, Mount Kina Balu, Borneo, Malaysia.

other common names

English: Long-fingered stream toad.

physical characteristics

In general, Ansonia are small, slender toads that lack parotoid glands. The snout protrudes over the tip of the lower jaw. The leg and digits are slender and the eyes relatively large. The males of Ansonia longidigita are 1.4–1.97 in (35–50 mm) and the females 1.77–2.75 in (45–70 mm) in snout-vent length. This toad is dark brown, with a few darker crossbars on the hindlimbs.

distribution

This toad is known only from Borneo.

habitat

Long-fingered slender toads live in lower and upper montane regions (up to 7,220 ft or 2,200 m) with intact forest.

behavior

Little is known.

feeding ecology and diet

As with many toads, ants are an important part of the diet.

reproductive biology

The call is a high trill. Breeding occurs near swift rocky streams, where males gather to call. The tadpoles are small and stream-adapted, with large ventral suctorial mouths that occupy part of the belly. However, like Atelopus, the number of

denticle rows is only two above and three below the mouth. In many ways, Ansonia appear to be ecological equivalents of Atelopus in the New World. However, research on the phylo-genetic relationships of toads using DNA data has shown that the similarities between Ansonia and Atelopus result from evolutionary convergence.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Harlequin frog

Atelopus varius

taxonomy

Phrynidium varium Lichtenstein and von Martens, 1856, Veragua, Panama.

other common names

English: Harlequin toad.

physical characteristics

These are often called harlequin frogs or toads because many of them are so brightly colored as to appear to be in a jester's costume. The coloration is usually a combination of markings of black and some starkly contrasting color such as yellow, green, orange, or red. In some populations the males and females are colored differently, in others they are similar. Males are about 1.06–1.57 in (27–40 mm), females 1.34–1.9 in (34–48 mm) in snout-vent length. Like most species of Atelopus, this one lacks a tympanum and cranial crests.

distribution

This toad is known from Costa Rica and Panama.

habitat

These toads inhabit humid lowland and lower montane forests.

behavior

These diurnal toads may be seen actively moving across open areas as if impervious to predators; adults sleep at night on large flat leaves of vegetation over montane streams. The author has encountered as many as 50 individuals in an hour. Toads of the genus Melanophryniscus behave similarly. Harlequin frogs have exceptional homing ability. Field experiments showed that 31 of 44 individuals that were displaced 32.8 ft (10m) from their point of capture returned to within 3 ft (1 m) of that spot in a week. Some individuals were faithful to a particular boulder for two years. Male harlequin frogs have pronounced aggressive encounters. One may chase and pounce on another male and use his body to squash his opponent. Males may also signal each other by raising a front foot and waving it in a circular motion in the air, either before or after a battle. Interestingly, males will tolerate each other more in the dry season, when limited wet areas necessitates that they crowd together. When the rains come, aggression is more pronounced. In the species Atelopus zeteki and Atelopus varius, the extremely potent toxin tetrodotoxin has been found in the skin. This compound was named for the fugu or pufferfish (Tetraodon), from which it was isolated. At the least, tetrodotoxin makes the toad bad-tasting; at worst, it is lethal to the predator. There is a link between being diurnal, brightly colored, and toxic. A predator can easily spot this gaudy toad during the day, but the experience of grabbing this prey will be unpleasant. The predator learns to avoid potential prey that have these visual characteristics.

feeding ecology and diet

They are known to feed on a diverse set of arthropods, including flies, wasps, ants, caterpillars, and spiders.

reproductive biology

There is apparently no courtship; the short buzzlike call serves a territorial function. Amplexus, as in other species of Atelopus, may last several days, with the female carrying the male around on her back. The eggs are completely cream-colored and are laid in strings, presumably in the streams in which the tadpoles are found.

The tadpole has an enlarged mouth and sucker that extends onto the belly. The tadpoles adhere to the undersides of rocks in swiftly flowing mountain streams.

conservation status

Their diurnal habits make these toads easy to observe. But this has led to the unsettling realization that well-established populations of the Costa Rican Atelopus varius have mysteriously disappeared since the mid-1980s. However, the species is not listed on the IUCN Red List.

significance to humans

In the past, this animal was exported in large numbers for the pet trade. It apparently has been one of the victims of the worldwide decline of amphibians. Most populations in Costa Rica appear to be extinct.

Houston toad

Bufo houstonensis

taxonomy

Bufo houstonensis Sanders, 1953, Fairbanks, Harris County, Texas, United States.

other common names

None known.

physical characteristics

Males range from 1.92–2.6 in (49–66 mm) and females from 2.24–3.15 in (57–80 mm). This toad resembles others in the

Bufo americanus group: The dorsal surfaces are very warty, with obvious larger warts and many smaller warts between. Some dark dorsal spots surround the larger warts. Cranial crests are moderately developed.

distribution

This toad is known from a few counties in southeast Texas in the United States.

habitat

This toad is usually associated with sandy soils in loblolly pine forests.

behavior

The Houston toad is one of the first frogs to call in the spring, in January or February, when the 24-hour minimum air temperature reaches 57°F (14°C).

feeding ecology and diet

Nothing is known.

reproductive biology

The call is a high-pitched, pleasant musical trill lasting four to 11 seconds. Males often begin calling at sunset from burrows and then move out to occupy the highest sites around a pond to continue calling. Amplexus lasts a minimum of six hours before oviposition. Choruses last three to five nights, unless cold weather intervenes. Pigmented eggs are laid in strings and hatch in as little as seven days. The time from oviposition to metamorphosis is relatively constant, from 60–65 days. Metamorphic young are 0.27–0.35 in (7–9 mm) in length. The species is known to hybridize in the wild with Bufo woodhousii and Bufo valliceps.

conservation status

The IUCN categorizes this species as Endangered. A captive breeding program was begun at the Houston Zoo.

significance to humans

Continued survival of this toad depends on effective management. Expansion of local golf courses and parks threatens to remove some of the species' critical habitat.

Marine toad

Bufo marinus

taxonomy

Rana marina Linnaeus, 1758, America.

other common names

English: Cane toad; French: Bufo géant; German: Aga-Kröte; Spanish: Sapo grande.

physical characteristics

This is a very large toad with a broad U-shaped furrow between the eyes. The parotoid glands are large and triangular. Adults may reach 9 in (230 mm) and weigh 3.3 lb (1.5 kg). A close relative, Bufo paracnemis, is even larger and may be as big as a dinner plate.

distribution

This large, rather plain toad is native to South and Central America, Mexico, and the south of Texas. Its closest relatives are in South America, so its presence in Central America and northward represents a gradual migration across the Isthmus of

Panama. It is one of the few frog species found on both sides of the Andes in northern South America.

habitat

In its natural habitat, this toad prefers secondary forests and open areas in lowland and foothill areas.

behavior

These toads breed opportunistically when there is rain, and the breeding may occur over several months. Both temporary and permanent ponds and edges of lakes are used.

feeding ecology and diet

In natural settings the marine toad eats a variety of arthropods, from large roaches to ants. The species does quite well around human populations. Adult toads will gather under streetlamps to prey on insects that gather there; the same toad may return to the same lamp night after night. They are well-known for eating from the food dishes of pet dogs and cats. A biologist saw one sit for hours nabbing flies around a large pile of excrement. Sometimes large, common pests are ideal study organisms. The first experimental studies of how a frog projects its tongue were done on Bufo marinus.

reproductive biology

The call is a very low-pitched trill, lasting for 10–20 seconds. The females produce up to 25,000 eggs during one spawning. In south Florida these toads will breed in swimming pools, depositing long gelatinous strings consisting of thousands of eggs, to the chagrin of homeowners. The tadpoles are small and black and often form large schools.

conservation status

This species is not listed by the IUCN. Informal but active extirpation efforts are underway in several areas where the species have been introduced.

significance to humans

The marine toad is also quite common in many tropical climates because of human introductions. It was introduced to the West Indies as early as the mid-nineteenth century, and to Hawaii, the Philippines, and Australia in the 1930s. The common name "cane toad" came from its intended use to control insect pests of sugar cane. The toad did quite well in its new home. In Australia, especially, it spread rapidly, becoming a pest and outcompeting many local animals. It has also caused economic damage by fouling water supplies used by cattle. Its notoriety in Australia has been recognized with a movie and a book with the title Cane Toads: An Unnatural History.

Common sunda toad

Bufo melanostictus

taxonomy

Bufo melanostictus Schneider, 1799, Orient.

other common names

English: Asian common toad, Asian toad, black-lipped toad, black-spined toad, common Asian toad, common Indian toad, Indian toad, keeled-nosed toad, Maharashtra stream toad, Southeast Asian broad-skulled toad.

physical characteristics

This is a rather typical-looking moderate-sized toad. Males are 2.24–3.27 in (57–83 mm) and females 2.56–3.34 in (65–85 mm). The distinctive features are the bony crests that border the eyes and extend from behind the eye to the parotoid gland, which is moderately large and oval. Like many Bufo, the body is generally warty, but the bony crest and warts are tipped with many small black spines of keratin; hence the name melanostictus.

distribution

Southwestern and southern China, Taiwan, Hainan; from Pakistan and Nepal through India to Sri Lanka; Andaman Islands, Sumatra, Java, Borneo, and Bali. It has apparently invaded Borneo recently.

habitat

The most common place to find these toads is in association with human dwellings. This toad seems to be at home in cities, as long as there is some temporary water for breeding.

behavior

Little is known, except for reproductive behavior.

feeding ecology and diet

Like many toads, it eats arthropods, especially ants.

reproductive biology

The mating call of this toad is a moderately pitched trill, sounding somewhat like a rattle. The tadpoles of these toads are typical Bufo tadpoles, small (0.47–0.63 in or 12–16 mm long) and black, without obvious modifications of the mouth-parts; in other words, they have no expanded lips or extra rows of denticles.

conservation status

Not threatened.

significance to humans

Its main significance to humans is that it thrives in human habitats and is actively expanding its range. How this might affect local species is unknown at present.

Golden toad

Bufo periglenes

taxonomy

Bufo periglenes Savage, 1966, 2 mi (3.22 km) east-northeast of Monteverde, Puntarenas Province, Costa Rica.

other common names

English: Alajuela toad, Monteverde toad; French: Crapaud doré; Spanish: Sapo dorado de Monteverde.

physical characteristics

This species is spectacular in that both sexes are brightly colored. Males are a uniform bright orange, and females are blackish green with red spots. The coloration of this toad makes it impossible to confuse with anything else. The males are 1.53–1.89 in (39–48 mm) in snout-vent length and the females 1.65–2.2 in (42–56 mm). The cranial crests are not well developed, and the tympanum and middle ear are absent.

distribution

The golden toad is known from two localities at elevations of 4,920–5,250 ft (1,500–1,600 m) along the continental divide of northwestern Costa Rica.

habitat

This toad is a denizen of the elfin, windswept montane rain-forests along the crest of the cordillera. The areas where it is known are part of the Monteverde Cloud Forest Preserve.

behavior

Although such bright colors are usually associated with skin toxins, this species has not been examined for these.

feeding ecology and diet

Not known.

reproductive biology

It is not clear whether this species has an advertisement call. The breeding of these toads is explosive and coincides with heavy thunderstorms. As many as several hundred males

emerge, but only about 100 females at most. Several males may battle, attempting to dislodge a male already in amplexus with a female. The eggs of this species are about 0.11 in (3 mm) in diameter, which is a little larger than the eggs of most Bufo, but they are laid in the typical strings. The tadpoles are about 1.18 in (30 mm) in length, which is larger than tadpoles of most species of Bufo. In addition, the larvae can develop in the absence of food. Mostly likely, the larger size of the eggs provides sufficient yolk supply for them to survive if food is not present.

conservation status

The golden toad is one of many frog species whose recent disappearance has caused much concern. After their discovery, these toads bred regularly each year until about 1988, when only a few emerged. In 1989 only one was observed, and thereafter none. The IUCN lists the species as Critically Endangered, although most experts believe it is extinct.

significance to humans

This beautiful toad is a reminder of the fragility with which some species pass their existence and a symbol for amphibian conservation.

Green toad

Bufo viridis

taxonomy

Bufo viridis Laurenti, 1768, Vienna, Austria. The exact taxonomic status of many populations assigned to this species is not clear because there are diploid, triploid, and tetraploid populations in various parts of the range that have been named as subspecies or full species. These populations differ in call characteristics as well as the number of sets of chromosomes.

other common names

English: European green toad; French: Crapaud vert; German: Wechselkröte; Spanish: Sapo verde.

physical characteristics

Males reach about 2.44–3.22 in (62–82 mm) in snout-vent length, and females may reach 3.9 in (100 mm); however, local populations in parts of the range are extremely variable in size. This toad has well-defined marbled green dorsal markings, usually with darker edges, against a tan background. The paratoid glands are oval and parallel to each other rather than diverging. Cranial crests are absent.

distribution

The green toad occurs in Europe east of the Rhine River, including the southern tip of Sweden; the Balearic Islands, Corsica, and Sardinia; western Asia, including Iran, Mongolia, and China; southwestern Asia and the Arabian Peninsula; and northern Africa, from Morocco to Libya.

habitat

The green toad is usually found in open, drier lowland areas in Europe and more mountainous regions in Asia.

behavior

The green toad is nocturnal; in cities these toads may congregate around street lamps and eat insects. Some physiological color change may occur in the intensity of the green marbling.

feeding ecology and diet

This toads eats arthropods and insects of all kinds; anecdotes report that it will starve rather than eat earthworms.

reproductive biology

The call is a high-pitched trill that lasts for about 10 seconds; it is said to resemble a bird more than a toad. Small (0.04 in or 1.2 mm diameter) blackish eggs (1,000–2,000) are laid in strings. Like most Bufo tadpoles, these are small (0.47–0.59 in or 12–15 mm) and blackish.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Yungas redbelly toad

Melanophryniscus rubriventris

taxonomy

Atelopus rubriventris Vellard, 1947, San Andrés, Salta Provice, Argentina.

other common names

None known.

physical characteristics

Individuals are about 1.57–1.77 in (40–45 mm) in snout-vent length. This is a moderately warty toad, but the warts appear to be glandular swellings. There are no parotoid glands. The head and snout are relatively short compared to Atelopus. The dorsum may be mostly black or may have some yellow spots. The belly and palms and soles are uniformly red-orange.

distribution

This species is known from the subtropical valleys of northwestern Argentina.

habitat

These toads live in humid hilly regions along small streams.

behavior

Like Atelopus, these toads are diurnal; they are also toxic. Melanophryniscus exhibit the same sort of unken reflex when disturbed as do the European fire-bellied toads, Bombina.

feeding ecology and diet

Nothing is known.

reproductive biology

The call of males is a soft, short trill. Although this species is often found near streams, the eggs are attached to vegetation in small bodies of standing water. The tadpoles are bottom dwellers in ponds.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Roraima bush toad

Oreophrynella quelchii

taxonomy

Oreophryne quelchii Boulenger, 1895, summit of Mount Roraima, Guyana.

other common names

None known.

physical characteristics

These small toads are about 0.78 in (20 mm) in snout-vent length. This species lacks cranial crests. The venter has brown and yellow blotches, and the dorsum is dark brown and warty. Species of Oreophrynella are distinctive in the morphology of the foot, in which the first digit is opposed to the others and the second toe is distinctly shorter than the remaining ones. Originally, it was thought that this foot functioned as a branch grasper, much as in the treefrog Phyllomedusa (Hylidae). However, observations of these toads in life indicate that the foot is used for clambering across rocks. The toads are basically walkers and rarely if ever hop. The number of vertebrae is reduced to six, which is probably related to the mode of locomotion.

distribution

This toad is found on Mount Roraima on the border of Venezuela and Guyana, one of the highlands of the Guianan shield region of South America consisting of flattened table-top mountains with steep sides, known as tepuis.

habitat

The few available data indicate that this species lives among boulders in dense vegetation on the mountaintops.

behavior

These toads do not leap or hop; rather, they walk slowly across rocks. When disturbed, they tuck their head, hands, and feet under the body and roll off of the rock face like a dislodged stone.

feeding ecology and diet

Nothing is known.

reproductive biology

The call of this species is not known with certainty, but that of a related species (O. huberi) was described as a shrill "pi, pi, pi." Development of the eggs is apparently direct; no tadpoles have ever been found. Females have been observed attending terrestrial egg clutches.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Brown tree toad

Pedostibes hosii

taxonomy

Nectophryne hosii Boulenger, 1892, Mt. Dulit, Sarawak, Borneo, Malaysia.

other common names

English: Boulenger's Asian tree toad, common tree toad.

physical characteristics

This is a moderately large toad, with males 2.09–3.07 in (53–78 mm) and females 3.5–4.1 in (89–105 mm). The dorsum is only moderately warty. A small parotoid gland is present; there is a slight bony ridge just behind the eye, but otherwise cranial crests are not obvious. Consistent with this toad's arboreal habits, the digital tips are slightly widened, but these are not true digital discs as found in species of the families Hylidae or Rhacophoridae. Female brown tree toads are often featured in pet enthusiast magazines because some of them are dark purple with yellow spots. The significance of this coloration is not known.

distribution

This apparently widespread species is found in Borneo, Sumatra, peninsular Malaysia, and Thailand.

habitat

Species of Pedostibes are perhaps the only truly arboreal toads. They are found in lowland primary forests and not in open areas.

behavior

Unlike many toads, brown tree toads apparently do not form breeding aggregations with large numbers of males calling.

feeding ecology and diet

Ants form the major part of the diet.

reproductive biology

The males make a call, which has been described as a slurred squawk. Adults breed at clear streams. The tadpoles are similar but not identical to those of Bufo. The color is dark brown, but not quite black as in Bufo. The tadpoles live in the side pools of streams.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Aquatic swamp toad

Pseudobufo subasper

taxonomy

Pseudobufo subasper Tschudi, 1838, Borneo.

other common names

None known.

physical characteristics

This is a large toad, with males 3.03–3.7 in (77–94 mm) and females 3.62–6.1 in (92–155 mm) in snout-vent length. In general, most toads have relatively unremarkable body shapes and are terrestrial. They have not really invaded the aquatic or arboreal niches. Pseudobufo subasper is an exception. This toad is basically a Bufo that has become an aquatic specialist. The feet are fully webbed, and the webbing is thin, in contrast to the rather thick webbing found in most toads. The nostrils are placed dorsally, and the fingers are slender and unwebbed. The vertebral column exhibits a reduction in ossification that is consistent with it being an aquatic species. Paratoid glands are present.

distribution

This toad is found in the Indonesian province of Kalimantan on the island of Borneo, Sumatra, peninsular Malaysia.

habitat

These toads are found associated with pools in swampy areas near large rivers.

behavior

Little information is available for these toads; it is not known when they call or breed.

feeding ecology and diet

Not known.

reproductive biology

Not known.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Chirinda toad

Stephopaedes anotis

taxonomy

Bufo anotis Boulenger, 1907, southeast Mashonaland, Zimbabwe.

other common names

English: Boulenger's earless toad, Chirinda forest toad, Mashonaland toad.

physical characteristics

These are moderately small toads about 1.57–1.77 in (40–45 mm) in snout-vent length. The cranial crests are poorly developed, and the tympanum is absent. The parotoid glands are large. The dorsum is not so much warty as granular, and the brown coloration renders this animal cryptic against dead leaves.

distribution

The Chirinda toad is known only from the Chirinda Forest in Zimbabwe and from forest in adjacent Mozambique.

habitat

This toad dwells in the leaf litter on the forest floor.

behavior

Little is known, except for reproductive behavior.

feeding ecology and diet

The diet consists of leaf-litter arthropods, mainly ants.

reproductive biology

It is questionable whether this species of Stephopaedes calls; no direct observations of vocalizations are known. Unlike most bufonids, this species breeds in restricted pools of water and in holes in the trunks of a particular species of tree. The eggs are about 0.1 in (2.5 mm) in diameter and are laid in short strings that quickly fall apart. The tadpoles are remarkable in having a crown of epithelial tissues forming a closed circle around the eyes and nostrils. It may function as an additional respiratory surface for the restricted habitats in which these tadpoles live.

conservation status

Although not listed by the IUCN, this species is considered to be vulnerable owing to its restricted distribution.

significance to humans

None known.

Resources

Books

Crump, Martha L. In Search of the Golden Frog. Chicago: University of Chicago Press, 2000.

Duellman, William E., and Linda Trueb. Biology of Amphibians. New York: McGraw-Hill, 1986.

Inger, Robert F., and Robert B. Stuebing. A Field Guide to the Frogs of Borneo. Kota Kinabalu: Natural History Publications, 1997.

Sanchíz, Borja. Salientia. Part 4: Encyclopedia of Paleoherpetology. Munich: Verlag Dr. Friedrich Pfeil, 1998.

Savage, Jay M. The Amphibians and Reptiles of Costa Rica. Chicago: University of Chicago Press, 2002.

Periodicals

Crump, Martha L. "Homing and Site Fidelity in a Neotropical Frog, Atelopus varius (Bufonidae)." Copeia 1986 (1986): 438–444.

Daly, John W., Robert J. Highet, and Charles W. Myers. "Occurrence of Skin Alkaloids in Non-dendrobatid Frogs from Brazil (Bufonidae), Australia (Myobatrachidae) and Madagascar (Mantellinae)." Toxicon 22 (1984): 905–919

Ford, Linda S., and David C. Cannatella. "The Major Clades of Frogs." Herpetological Monographs 7 (1993): 94–117.

Graybeal, Anna. "Phylogenetic Relationships of Bufonid Frogs and Tests of Alternate Macroevolutionary Hypotheses Characterizing their Radiation." Zoological Journal of the Linnean Society 119 (1997): 297–338.

Graybeal, Anna, and David C. Cannatella. "A New Taxon of Bufonidae from Peru, with Descriptions of Two New Species and a Review of the Phylogenetic Status of Supraspecific Bufonid Taxa." Herpetologica 51 (1995): 105–131.

McDiarmid, Roy W. "Comparative Morphology and Evolution of Frogs of the Neotropical Genera Atelopus, Dendrophryniscus, Melanophryniscus, and Oreophrynella." Science Bulletin of the Los Angeles County Museum of Natural History 12 (1971): 1–66.

McDiarmid, Roy W., and Stefan Gorzula. "Aspects of the Reproductive Ecology and Behavior of the Tepui Toads, Genus Oreophrynella (Anura, Bufonidae)." Copeia 1989 (1989): 445–451.

Roessler, Martha K. P., Hobart M. Smith, and David Chiszar. "Bidder's Organ: A Bufonid By-product of the Evolutionary Loss of Hyperfecundity." Amphibia-Reptilia 11 (1990): 225–235.

Wake, Marvalee H. "The Reproductive Biology of Nectophrynoides malcolmi (Amphibia: Bufonidae), with Comments on the Evolution of Reproductive Modes in the Genus Nectophrynoides." Copeia 1980 (1980): 193–209.

David Cannatella, PhD