Ghost Frogs (Heleophrynidae)

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Ghost frogs

(Heleophrynidae)

Class Amphibia

Order Anura

Family Heleophrynidae

Thumbnail description
Medium-sized frogs with triangular discs on the fingers and toes

Size
1.4–2.6 in (35–65 mm)

Number of genera, species
1 genus; 6 species

Habitat
Montane forest

Conservation status
Endangered: 1 species; Vulnerable: 1 species

Distribution
South Africa, Lesotho, and Swaziland

Evolution and systematics

No fossils are known. The family has its closest relatives in South America and Australia, which is interesting further evidence of continental drift and the great age of this family. Although it was placed earlier as a subfamily within the Leptodactylidae, it now is recognized as a distinct family. No subfamilies are recognized.

Physical characteristics

The large, triangular discs on the fingers and toes are characteristic, along with a vertical pupil and a dorsal color pattern usually consisting of large spots on a brown or green background. The adult males of the smaller species, such as Heleophryne orientalis, do not exceed 1.4 in (35 mm), while the females of larger species grow to more than 2.6 in (65 mm). The body is flattened with protruding eyes, and the limbs are thin and long. The pupil is vertical, the tongue is disc-shaped, and the upper jaw bears teeth. The frogs swim well, with toes that are nearly fully webbed in some species. Most species have large dark spots on a paler background. The background color is typically tan to pale gray, but dark brown, yellowish, or bright green individuals are found. The tadpoles are streamlined and cling to rocks in fast-flowing streams. Most tadpoles have no keratinized jaw sheaths, except Heleophryne rosei, which has only a lower jaw sheath.

Distribution

This family is endemic to the high mountains and escarpment of the Drakensberg range and its extensions in southern Africa. Species are found from sea level to 9,843 ft (3,000m). The recent loss of natural forest has caused streams to dry up, especially in areas where pines have been planted. Two species have very restricted ranges associated with pine plantations.

Habitat

Adults are found in forest or riverine forest. They may move 0.6 mi (1 km) or more from streams outside the breeding season, even into alpine grassland. The larvae are restricted to fast-flowing streams with rocky substrates. They are found attached to rocks in the fast current and also in quiet backwaters.

Behavior

The frogs congregate after the rains near waterfalls or other fast-flowing water once the rivers subside. After breeding, the adults stay near the stream to feed but will move long distances away from water until the next rainy season heralds a new breeding season. Adults remain concealed in cracks or in holes during the day, emerging at night to feed and breed.

Feeding ecology and diet

These frogs take a range of insects, arthropods, and snails. They readily eat smaller species of frogs.

Reproductive biology

During the breeding season the body skin becomes loose, forming large, slimy folds, with the toes fringing with web. Males move into the streams as sexual activity increases and remain aquatic until the breeding season ends. The loose skin provides additional surface area, so that the males can obtain oxygen from the water. The breeding season is from spring to mid-summer (October to January in southern Africa). The male calls from within the spray zone of a waterfall or concealed in a rock crack or under a large rock. In some species the call is loud, but in others it is quiet, audible only from 10 ft (3 m) or less. Eggs are laid in quiet backwaters, but they also may be laid out of water in seepage zones, singly in slow-flowing areas and small pools. Some species attach their eggs under rocks in a stream. The eggs develop into free-swimming tadpoles. There is no parental care. The tadpoles graze on algae growing on rocks, leaving grazing trails.

Conservation status

The family is endemic to the Drakensberg mountain chain running through South Africa, Lesotho, and Swaziland. Two species are common, with wide distributions, while one is classified as Vulnerable (Heleophryne rosei) and another as Endangered (Heleophryne hewitti) by the IUCN. H. hewitti is known from short sections of only four rivers, all within 6.2 mi (10 km) along the slopes of the Elandsberg Mountains. H. rosei is restricted to a few streams on one side of Table Mountain in Cape Town, South Africa.

Significance to humans

These animals are not used for food. Although the skin contains toxins that protect the animal from mammalian predators, these toxins are not significant for humans.

Species accounts

List of Species

Natal ghost frog
Rose's ghost frog

Natal ghost frog

Heleophryne natalensis

taxonomy

Heleophryne natalensis Hewitt, 1913, eastern South Africa, Lesotho and Swaziland.

other common names

Spanish: Sapo de espuela de los llanos.

physical characteristics

The body is flattened, and the eyes are large and protruding. The back is brown to black with green or yellowish markings. These frogs have a marbled throat and triangular discs on the fingers and toes that are only slightly wider than the fingers and toes themselves.

distribution

This species is known from the eastern mountains of South Africa, including those in Lesotho and Swaziland.

habitat

These frogs are found where the streams are fast flowing in natural forest. Adults can be found up to 0.6 mi (1 km) from water, in holes in banks and cliffs.

behavior

The adults sometimes can be seen during the day as they sit and wait for prey in the splash zone of waterfalls. They mostly hide under rocks in the river during the day, however, and come out after dark.

feeding ecology and diet

The Natal ghost frog eats small insects, spiders, and other arthropods.

reproductive biology

The males call from vegetation near streams or from rock ledges or under large boulders within the spray zone of small waterfalls. The eggs are deposited under rocks in a stream. Within days they hatch into free-living tadpoles with as many as four upper rows and 17 lower rows of labial teeth.

conservation status

Not threatened.

significance to humans

None known.

Rose's ghost frog

Heleophryne rosei

taxonomy

Heleophryne rosei Hewitt, 1925, Table Mountain above Cape Town, South Africa.

other common names

English: Thumbed ghost frog, Table Mountain ghost frog, Skeleton Gorge ghost frog.

physical characteristics

This is a moderately sized frog, with the larger female up to 2.4 in (60 mm) and the smaller male up to 2 in (50 mm). The coloration of adults is striking: often a pale green background with purple to brown blotches. The fingers and toes have large triangular terminal discs. A rudimentary thumb is present as a distinct inner metacarpal tubercle. The feet are half webbed, with one phalanx of the fifth toe free of web. The tadpole has neither an upper nor lower jaw sheath but up to 17 rows of posterior labial teeth. The tadpole also has a large oral disc and is able to climb up wet vertical rock faces.

distribution

This species is known only from the eastern side of Table Mountain in Cape Town in a few perennial streams.

habitat

The typical habitat of this frog includes moist, forested gorges, with vertical rock faces covered with moss.

behavior

The frogs are found on rock ledges or up in vegetation at night, retreating under large rocks and in cracks of rocks during the day.

feeding ecology and diet

These frogs eat a range of small insects and other forest arthropods.

reproductive biology

Breeding starts in November when the streams are low but the temperature is high. The male's secondary sexual characters include a number of small black spines on the outside surfaces of the forearms, on the back, and on the top of the back legs. The eggs have not been found, but in other species they are deposited under rocks in streams. The tadpoles develop for about 12 months.

conservation status

This species is listed as Vulnerable by the IUCN and in the South African Red Data Book. The population is small, geographically restricted, and threatened by the plantations of pines on the mountain that cause the streams to dry up.