Amero-Australian treefrogs

(Hylidae)

Class Amphibia

Order Anura

Family Hylidae

Thumbnail description
Small to large primarily arboreal frogs with expanded, adhesive discs on the digits

Size
0.8–4.8 in (20–120 mm)

Number of genera, species
42 genera; 854 species

Habitat
Primarily tropical and subtropical forests, some savannas, grasslands, and deserts; a few species inhabit elevations above the tree line

Conservation status
Critically Endangered: 6 species; Endangered: 5 species; Vulnerable: 5 species; Lower Risk/New Threatened: 5 species; Data Deficient: 8 species

Distribution
Most of the New World, Australia, and New Guinea, and discontinuously in Eurasia

Evolution and systematics

The earliest fossil Hylidae are from the Paleocene of Brazil; elsewhere, fossil hylids are known from as early as the Miocene in Australia, the Oligocene in North America, the Miocene in Europe, and the Pleistocene in Japan. The meager fossil data are consistent with a Gondwanan origin of the family, presumably in South America after its separation from Africa. Independent dispersals from South America were to Australia via Antarctica and to North America and subsequently to Eurasia.

Treefrogs of the family Hylidae presumably are related most closely to other families of frogs in the New World that also have the two halves of pectoral girdle overlapping ventrally (arciferal conditions and intercalary elements between the penultimate and terminal claw-shaped phalanges). These families include Centrolenidae, which differ by having T-shaped terminal phalanges, tarsal elements fused throughout their lengths (fused proximally and distally in Hylidae), and 10 pairs of chromosomes (11 or more in Hylidae). The monotypic Allophrynidae differs by lacking teeth on the maxillaries and premaxillaries and intercalary elements in the digits, but the T-shaped terminal phalange is offset ventrally, as in Hylidae.

Five subfamilies are recognized:

Hemiphractinae

The eggs are brooded on the back of, or in a dorsal pouch of females; the embryos have large, sheet-like gills that at least partially envelop them. Most species have direct development. In those in which the eggs hatch as tadpoles, the spiracle is ventrolateral in position but moves to a lateral position in Gastrotheca. The intercalary elements are cartilaginous, and the terminal phalange is offset ventrally. The constricted pupil of the eye is horizontally elliptical. The diplod number of chromosomes is 26 (28 and 30 in some species of Flectonotus).

The subfamily contains five genera and 71 species; it is distributed principally in montane regions from Costa Rica to northwestern Argentina, the Guiana Highlands, and eastern Brazil.

Hylinae

The eggs are deposited in water, on vegetation above water, or in subterranean nests near water; all eggs hatch as free-swimming tadpoles, which have a lateral spiracle. The intercalary elements are cartilaginous, and the terminal phalange is offset ventrally. The constricted pupil of the eye is horizontally elliptical. The diploid number of chromosomes is 24, but this number is reduced to 22 in Acris and increased to 30 in many species of Hyla and to 34 in Osteopilus brunneus. The subfamily contains 26 genera with more than 500 species; it has the same distribution as the family, except that it is absent in the Australo-Papuan region.

Pelodryadinae

The eggs are deposited in water or, in a few species, on vegetation above water. The free-swimming tadpoles have filamentous gills and a lateral spiracle. The intercalary elements are cartilaginous, and the terminal phalange is offset ventrally. The constricted pupil of the eye is horizontally elliptical (vertically elliptical in Nyctimystes). The diploid number of chromosomes is 26 (24 in Litoria infrafrenata and 30 in Litoria angiana). The subfamily contains three genera with about 150 species; it is widespread in Australia and New Guinea. Two species are endemic to the Bismarck Archipelago and Solomon Islands, and three Australian species have been introduced into New Zealand and New Caledonia.

Phyllomedusinae

The eggs are deposited on vegetation above water; the embryos have large, branched gills; and the free-swimming tadpoles have a ventrolateral spiracle. The intercalary elements are cartilaginous, and the terminal phalange is offset ventrally. The constricted pupil of the eye is vertically elliptical. The diploid number of chromosomes is 26. The subfamily contains five genera with 70 species; it is widely distributed in tropical parts of Mexico, Central America, and South America.

Pseudinae

These aquatic frogs deposit eggs in water; the free-swimming tadpoles have feathery gills and a lateral spiracle. The intercalary elements are elongated and ossified; the terminal phalange is essentially in the same plane as the other phalanges. The constricted pupil of the eye is horizontally elliptical. The diploid number of chromosomes is 24. Two genera contain seven species; the subfamily is distributed widely east of the Andes in tropical South America and on the island of Trinidad.

Physical characteristics

The family is characterized by a suite of internal features that distinguish Hylidae from other families. The two halves of the pectoral girdle overlap (arciferal condition); the vertebrae are procoelous, and the first two presacral vertebrae are not fused. The coccyx has a bicondylar (two-headed) articulation with the expanded sacrum. Neopalatine and quadratojugal bones usually are present. An intercalary element (usually cartilaginous) is present between the terminal and penultimate phalanges in each digit of the hand and foot, and, except for Pseudinae, the terminal segment of each digit is offset ventrally. The terminal phalanges are claw-shaped, and the terminal segment of each digit typically is expanded into an adhesive disc.

Several hylid frogs have casque heads, in which the skin on the head is co-ossified with expanded underlying dermal bones in the skull. Casque heads are especially well developed in Aparasphenodon, Corythomantis, Hemiphractus, Trachycephalus, and Triprion. In some of these frogs (e.g., Aparasphenodon and Triprion), the upper lips are flared outward, and an additional bone, the prenasal, is present; a different bone, the internasal, is present in Pternohyla. Some species of Gastrotheca and Osteocephalus have bony ridges on the skull, and Anotheca spinosa has bony spines directed upward on the back of the skull. All hylids have teeth on the maxillae and premaxillae, and most have teeth on the vomers. Gastrotheca guentheri is the only frog known to have true teeth on the dentary bones in the lower jaw, but Hemiphractus and Phyllodytes have bony projections (odontoids) on the anterior ends of the dentaries in the lower jaw.

Prominent glands are present on the top of the head in some species of Litoria, especially Litoria splendida, and parotoid glands in the shoulder region are present in many species of Phyllomedusa. The dermis of the dorsal skin in some arboreal hylids (e.g., Gastrotheca weinlandii, Phyllomedusa bicolor, and P. vaillanti) contains small, vascularized bony plates (osteoderms) from which small lamellar spines protrude into the epidermis. Presumably, these structures impede water loss through the skin on the body.

Most treefrogs have rather slender bodies and long limbs. The terrestrial and fossorial Cyclorana in Australia and the carnivorous Hemiphractus in South America, however, have robust bodies and proportionately shorter limbs. All hylid frogs, except pseudines, have ventrally offset terminal discs on their digits; these discs are expanded and adhesive in arboreal species. With the exception of most phyllomedusines, the feet are at least one-half webbed. The fingers may be webbed or not. The fingers are fully webbed in several arboreal species, some of which (e.g., Agalychnis craspedopus and Hyla miliaria) bear thin flaps of skin at the outer edges of the limbs. Other dermal modifications include a fleshy proboscis in Hemiphractus and eyelid "horns" in some species of Gastrotheca.

Most hylids have a prominent tympanum (eardrum). Males of most hylid frogs have a single, subgular vocal sac, which is inflated while they perch on the ground or vegetation. Osteocephalus, Phrynohyas, and Trachycephalus call while floating on water. In these frogs the vocal sacs are paired and located behind the angles of the jaws; when inflated, they form balloon-like structures that extend above the head and thus do not inhibit the floating frog. Males of most species develop nuptial excrescences in the breeding season. Commonly, they are keratinized, and in some stream-breeding species (e.g., Ptychohyla) they take the form of clusters of spines; a cluster of spines also is present on the humerus in Hyla armata. Male Plectrohyla and gladiator frogs (Hyla boans group) have a sharp spine at the base of the thumb. Burrowing hylids (Cyclorana and Pternohyla) have enlarged, spade-like inner metatarsal tubercles.

Treefrogs vary tremendously in size and coloration. With a few exceptions, females are larger than males. Several species have snout-vent lengths of less than 1 in (25 mm). The smallest is Litoria microbelos in northern Australia; adults of both sexes attain snout-vent lengths of only 0.65 in (16 mm). The largest species is Hyla vasta on the island of Hispaniola in the West Indies; females are known to exceed 4.8 in (142 mm). The exceptions are the gladiator frogs and relatives in South and Central America, males of which aggressively defend their nesting sites from other males.

In most hylid frogs the dorsum is brown or green, usually with darker markings. Others have a yellow or gray dorsum, and some, such as Hyla picturata with a gaudy red-and-yellow dorsum, are more boldly marked. The ventral surfaces typically are white or pale yellow, but many species have brown or black spots or mottling on the belly; males of many species have bright yellow or dark gray vocal sacs. The most striking

aspects of coloration are the so-called flash colors on the flanks and surfaces of the hind limbs, which are not visible when the frogs are in a resting position. These flash colors are especially colorful in some species of Agalychnis and Phyllomedusa, in which the flanks are marked variously with black, blue, yellow, and white bars. Others, such as several species of Scinax, have bright yellow or red bars or spots on the posterior surfaces of the thighs.

With the exception of some Hemiphractinae, all hylid frogs have aquatic, free-swimming, feeding tadpoles, which have a sinistral spiracle and keratinized jaw sheaths. The oral disc usually is directed anteroventrally and lacks marginal papillae on the median part of the upper lip; elsewhere the lips typically bear one or two rows of marginal papillae. Tadpoles of many species that develop in streams have enlarged suctoral oral discs, but the tadpoles of Duellmanohyla and Phasmahyla have upturned, umbelliform oral discs in the form of an inverted umbrella. Labial teeth generally are present, but they are absent in one group of South American Hyla; the labial teeth are reduced greatly in oophagous (egg-eating) tadpoles. Most tadpoles that develop in ponds have two upper rows and three lower rows of labial teeth; the number of rows is increased greatly in many tadpoles that develop in torrential streams. The maximum is 17 upper rows and 21 lower rows of labial teeth.

Most hylid tadpoles have total lengths of less than 2 in (50 mm); in those that develop in ponds, the body is about one-third

of the total length. The largest known tadpole is that of Pseudis paradoxa, which reaches a total length of more than 10 in (25 cm). Tadpoles that develop in streams have proportionately longer, more muscular tails with lower fins than those that mature in ponds.

Distribution

The family has a continuous distribution throughout most of the New World, including the West Indies but excluding Arctic North America and southern South America. It is distributed widely in Australia and New Guinea, and two species also inhabit the Bismarck Archipelago and the Solomon Islands. A few species of Hyla occur in Europe, southwestern Asia, discontinuously in eastern Asia (including the Japanese Archipelago), and Mediterranean North Africa as well as on the Azores, Madeira, and the Canary Islands in the Atlantic Ocean. Some Australian species have been introduced into New Caledonia and New Zealand, and some North American species have been introduced onto islands in the West Indies. One West Indian species has been introduced into Florida.

Habitat

Hylid frogs are most diverse in tropical and subtropical humid forests, especially in the Amazonian rainforest, where as many as 40 species may occur together. Hylids also are numerous in montane cloud forests, especially in Mexico, Central America, and New Guinea, as well as in the coastal forests of southeastern Brazil and the lowland forests of northern Australia and New Guinea. In Australia some species of Litoria and all species of Cyclorana, most of which inhabit grasslands and deserts, are terrestrial or even fossorial, a habit also characteristic of Pternohyla in Mexico. Members of the sub-family Pseudinae are aquatic. By day most hylids secrete themselves in arboreal situations, such as under the loose bark of trees, on the undersides of leaves, and in bromeliads. A few that breed in mountain streams seek diurnal shelter under rocks at the edges of streams or in rock crevices.

Behavior

Nearly all species are nocturnal; Acris in North America also is active by day, and some montane species are active by day. In the latter category are the Andean Hyla labialis and the Guatemalan Plectrohyla glandulosa, both of which bask on bushes or rocks. Thus, hylids are encountered mostly at night, especially after rains, when they feed and breed. Although adults may spend the day in seclusion, most treefrogs perch on branches, leaves, or grasses at night. Aside from natural diurnal retreats, treefrogs also utilize human-made structures, including window shutters, thatch roofs, water tanks, and cisterns.

Some hylids that live in arid regions survive long dry periods by special behaviors to prevent desiccation. In the Australian deserts Cyclorana dig burrows with spadelike tubercles on the hind feet; they remain underground for many months. Dehydration is prevented by shedding layer upon layer of skin, which hardens into an impermeable cocoon. Some Phyllomedusa in dry regions of South America have lipid glands in the skin. The secretion from these glands is wiped by the hands and feet over the entire body so as to provide an almost impermeable covering that allows the frogs to remain exposed to air for long periods of time. Some of the casqueheaded treefrogs (e.g., Gastrotheca, Trachycephalus, and Triprion) back into bromeliads, where water exists at the bases of the leaf axils, or tree holes with water inside; they plug the openings with their bony heads. Treefrogs living in temperate regions hibernate below ground. At least two species (Hyla versicolor and Pseudacris crucifer) have large quantities of glycerol in their tissues, which acts as an antifreeze; these frogs can tolerate temperatures well below freezing.

Territorial behavior in hylids mostly is acoustic; males of many species are known to emit territorial or aggressive calls in the presence of conspecific males. Such calls usually define a given calling site; in cases where calling fails, males have been observed to grapple or even bite one another. Male gladiator frogs in the American tropics defend their excavated nests by attacking intruders with the sharp spines at the bases of their thumbs. Such attacks may result in deep cuts, punctured eardrums, or even death. At least some of the stream-breeding Plectrohyla in Central America presumably also incur damage with their thumb spines, inasmuch as some males have scarred bodies. Captive Anotheca spinosa have been seen to puncture the body of another individual in the same tree hole with the sharp spines on their heads.

Hylid frogs are prey for many kinds of animals, especially snakes. Avoidance of predation principally is by the escape behavior of leaping to another branch or leaf; this is carried to an extreme by some species (e.g., Agalychnis moreletii and

Anotheca spinosa) by "parachuting" for a long distance from a high limb. The terrestrial Litoria nasuta in Australia escapes by a series of long leaps. Some small species with fully webbed feet are capable of skittering across the surface of the water. Acris crepitans skitters after an initial leap from land, and Scarthyla goinorum is capable of leaping off a low bush to skitter on the water and then jump up onto another bush.

In an encounter with a potential predator, some Hyla and Phyllomedusa feign death by tucking their limbs close to the body and remaining motionless on their backs. In contrast, Hemiphractus turn their heads up, open their mouths so as to display an orange tongue, and even snap at a potential predator. The volatile, alkaline skin secretions of Phrynohyas are insoluble in water and have a deleterious effect on mucous membranes of the eyes and mouth; consequently, most predators avoid these frogs.

Tadpoles of most species seem to exist independently from conspecifics, but tadpoles of Hyla geographica and Phyllomedusa vaillanti form schools of hundreds of individuals. This behavior may result in less predation. Otherwise, tadpoles avoid predation by either remaining motionless or rapidly hiding amidst aquatic vegetation.

Feeding ecology and diet

All hylids seem to be sit-and-wait predators that feed on a wide variety of arthropods; the selection of food depends primarily on the size of the prey. A few species are specialists on certain kinds of insects. Sphaenorhynchus lacteus feeds almost exclusively on ants, and Hyla leucophyllata feeds mostly on moths. The large-headed, broad-mouthed Hemiphractus eat large insects and other frogs.

Reproductive biology

Throughout temperate regions and the lowland tropics, hylid frogs respond to rains by moving to breeding sites, either temporary or, less frequently, permanent ponds. The length of the breeding season is determined by the period of rainfall; some northern species (e.g., Pseudacris crucifer) even call from the edges of ponds with ice on the water and snow on the banks. Species in dry regions tend to be explosive breeders that are active for only a day or so after heavy rains form temporary ponds. In contrast, hylids inhabiting humid rainforests and montane cloud forests may breed throughout the year in streams and ponds.

In those species that breed in ponds and streams, males congregate for breeding; after a heavy rain in tropical regions, breeding sites may have hundreds of individuals of several species calling at the same time. The calls vary from soft "peeps" to loud "growls." The calls of some species consist of only one note repeated at intervals of a few seconds to several minutes; other calls are a series of notes. In those species that call from bromeliads or tree holes, males usually are solitary. Females are attracted to the breeding site by the calls. Amplexus is axillary.

Diverse reproductive modes are employed by hylid frogs:

• Eggs are deposited in water (ponds or streams), and tadpoles develop in water: most Hylinae and Pelodryadinae and all Pseudinae.
• Eggs are deposited, and early-stage tadpoles develop in natural or constructed basins; subsequent flooding releases tadpoles into ponds or streams: Hyla boans group.
• Eggs are deposited in a foam nest floating on water in a pond; tadpoles develop in the pond: Scinax rizibilis.
• Eggs are deposited, and tadpoles develop in subterranean nests near ponds; subsequent flooding releases feeding tadpoles into ponds: Hyla leucopygia.
• Eggs are deposited on vegetation above water; feeding tadpoles develop in ponds or streams: all Phyllomedusinae and a few Hylinae and Pelodryadinae.
• Eggs are deposited, and tadpoles develop in bromeliads or cavities in trees: several species of Hylinae.
• Eggs are deposited in a pouch on the dorsum of the female; feeding tadpoles live in ponds: some Gastrotheca.
• Eggs are deposited in the dorsal pouch or on the back of the female; nonfeeding tadpoles live in bromeliads or tree holes: Flectonotus.
• Eggs are deposited in the dorsal pouch or on the back of a female; eggs hatch as froglets: Cryptobatrachus, Hemiphractus, Stefania, and some Gastrotheca.

At high latitudes and high elevations, as well as in arid environments, females usually deposit only one clutch of eggs per year, but at lower latitudes, especially in the lowland humid tropics, females may lay several clutches per year. Clutch size correlates with female body size within a given reproductive mode. Females of large species, such as Hyla rosen-bergi and Phrynohyas venulosa, that deposit small eggs in water have clutches in excess of 2,000 eggs, whereas in small species, such as Pseudacris ocularis, clutches consist of only about 100 eggs. Species that deposit eggs on vegetation over water have smaller clutches, ranging from 10 in the small Hyla thorectes to more than 250 in the large Phyllomedusa bicolor. Clutch size is less than 100 eggs in those species of Gastrotheca that transport eggs that hatch as tadpoles, whereas in those hemiphractines that carry eggs that hatch as froglets, clutches typically contain fewer than 15 proportionately much larger eggs.

No parental care exists among most hylid frogs, but female hemiphractines carry their eggs several weeks or months, depending on the stage at which the eggs hatch. The ultimate in parental care exists in several species that deposit their eggs in bromeliads or tree holes, where food is scarce. After deposition of a clutch of fertilized eggs, the female, accompanied or not by the male, returns to the breeding site and deposits additional fertilized or unfertilized eggs, which are eaten by the tadpoles. This behavior is known only in a few hylines (Anotheca spinosa, Osteocephalus oophagus, Osteopilus brunneus, and Phrynohyas resinifictrix) in tropical America.

Conservation status

According to the IUCN, six species are Critically Endangered; five are Endangered; five are Vulnerable; five are Lower Risk/Near Threatened; and eight are Data Deficient.

Habitat destruction imperils many species of hylid frogs. This is especially evident in montane regions, where many species have limited distributions. Some of the species of Hyla, Plectrohyla, and Ptychohyla have not been seen in recent years in areas where they were common before logging and stream pollution. Likewise, the conversion of dry tropical forests to agriculture seems to have limited greatly the distributions of such species as Triprion spatulatus. Chytrid fungus may be responsible for drastic declines or the extinction of many species, such as Hyla calypsa and H. xanthosticta in Central America and Nyctimystes dayi and at least three species of Litoria in northeastern Australia.

Significance to humans

Hylid frogs are not among those species commonly eaten by Europeans and North Americans, but many indigenous peoples in the American tropics and in the Australo-Papuan region catch and eat a variety of larger hylids, especially Hyla boans and Osteocephalus taurinus in the Americas and Nyctimystes in New Guinea. Indigenous people in New Guinea also eat tadpoles of Litoria and Nyctimystes, and the large tadpoles of Pseudis paradoxa are eaten in South America. Australian Aborigines unearth estivating Cyclorana platycephala and squeeze water out of them before replacing the frog in its burrow. Before going on a hunt, some indigenous people in the upper Amazon Basin lick the skin secretions of Phyllomedusa bicolor; this has a hallucinogenic effect.

Species accounts

List of Species

Riobamba marsupial frog

Gastrotheca riobambae

subfamily

Hemiphractinae

taxonomy

Hyla riobambae Fowler, 1913, Riobamba, Chimborazo, Ecuador. Before 1972, the frog was referred to as Gastrotheca marsupiata, a name now restricted to a species in Peru and Bolivia.

other common names

English: Ecuadorian marsupial frog; Spanish: Rana marsupial.

physical characteristics

Males are 1.4–2.3 in (34–57 mm) long, and females are 1.4–2.7 in (34–66 mm) long. A stout-bodied frog with a rounded snout. The skin on the dorsum is smooth or areolate, and the skin on the venter is granular. The limbs are moderately short, and the terminal disks on the digits are only slightly wider than the rest of the digit. Females have a dorsal pouch with an aperture placed posteriorly. The dorsum is tan or various shades of green, with or without darker green or brown markings; the venter is cream with or without gray or brown spots.

distribution

Found at elevations of 5,150–10,400 ft (1,590–3,220 m) in the Andes of northern and central Ecuador.

habitat

Montane grasslands, cultivated fields, and gardens in cities.

behavior

Terrestrial and primarily nocturnal; it finds diurnal refuges in crevices in stone walls, rock piles, terrestrial bromeliads, and agave plants.

feeding ecology and diet

A variety of arthropods, especially beetles.

reproductive biology

Males call from the ground or rocks; the call is "wraaackack-ack." Although a given male may breed several times a year, females breed only once per year. Females approach males, and mating takes place on land. Once in amplexus, the female elevates the cloaca, and the male exudes seminal fluid and, with his feet, spreads the fluid between the female's cloaca and the opening of the brood pouch. As the female exudes eggs, the male pushes the eggs with his feet over the back of the female and into the pouch. The incubation period of the 64–166 eggs in the pouch is 70–108 days. Tadpoles hatch in the pouch; their wriggling results in the female's sitting in shallow water. Parturition is partly spontaneous and partly assisted by the female, who distends the opening of the pouch with her hind feet and inserts one or both feet into the pouch and scoops out tadpoles. Newly released tadpoles have small hind-limb buds and begin feeding in the water in shallow grassy ponds or irrigation ditches within one to two days after release. Metamorphosis occurs 4–12 months after parturition.

conservation status

Although not listed by the IUCN, the Riobamba marsupial frog is threatened by pesticides that accumulate in the water where tadpoles develop and by chytrid fungus.

significance to humans

None known.

Sumaco horned treefrog

Hemiphractus proboscideus

subfamily

Hemiphractinae

taxonomy

Cerathyla proboscidea Jiménez de la Espada, 1871, Sumaco, Napo, Ecuador.

other common names

None known.

physical characteristics

Males are 1.8–2.0 in (43–50 mm) long; females are 2.3–2.7 in (57–66 mm) long. The Sumaco horned treefrog is a bizarre frog with a triangular head; fleshy, pointed snout; prominent tubercles on the upper eyelids; depressed body; and neural spines of vertebrae evident on the back. The dorsum is brown or tan with green, brown, or gray marks on the body and bars on the limbs; the venter is brown with tan or orange spots.

distribution

Upper Amazon Basin and lower slopes of the Andes in southern Colombia, Ecuador, and Peru.

habitat

Humid lowland and lower montane forest.

behavior

Nocturnal and arboreal. Defensive display consists of opening the mouth and exhibiting a bright yellow tongue.

feeding ecology and diet

Large arthropods, small lizards, and other frogs.

reproductive biology

Females carry up to 26 large eggs that adhere to her back; eggs undergo direct development into small frogs.

conservation status

Not threatened.

significance to humans

None known.

Northern cricket frog

Acris crepitans

subfamily

Hylinae

taxonomy

Acris crepitans Baird, 1854, northeastern United States. Two subspecies are recognized.

other common names

German: Grillenfrosch; French: Acris-grillon; Spanish: Rana grillo.

physical characteristics

Males are 0.7–1.2 in (17–28 mm) long; females are 1.0–1.5 in (25–38 mm) long. The dorsum is weakly tubercular, and the venter is smooth. The snout is acutely rounded, and the discs are not expanded; the toes are about four-fifths webbed. The dorsum is tan with brown or green markings, including a triangle on the head, a mid-dorsal stripe, and bars on the upper lips. The venter is white, and the posterior surfaces of the thighs are white with a longitudinal dark brown stripe.

distribution

Eastern North America.

habitat

The vicinity of permanent ponds, marshes, and slow-moving streams.

behavior

Nocturnal and diurnal; they are terrestrial and semiaquatic.

feeding ecology and diet

Feed under and on the surface of the water on a variety of small arthropods.

reproductive biology

Throughout the warm season of the year, males call from shallow water or floating vegetation; the call is a series of clicks. Amplectant pairs deposit up to 400 eggs singly or in clutches of two to seven eggs in shallow water. The eggs hatch in three to four days into small, solitary tadpoles that require five to seven weeks before metamorphosis.

conservation status

Not threatened.

significance to humans

None known.

Spiny-headed treefrog

Anotheca spinosa

subfamily

Hylinae

taxonomy

Hyla spinosa Steindachner, 1864, Brazil (in error). From 1939 to 1968 the frog was known as Anotheca coronata (Stejneger).

other common names

Spanish: Rana de coronata.

physical characteristics

Males are 2.5–2.7 in (60–65 mm) long; females are 2.4–3.0 in (58–73 mm) long. The head is casqued with sharp, upwardly pointing spines. The dorsum is brown with darker brown markings; the venter is black.

distribution

Discontinuous from central Veracruz, Mexico, to central Panama.

habitat

Humid forests at elevations of 300–5,800 ft (90–1,800 m).

behavior

Nocturnal and arboreal.

feeding ecology and diet

Feed on arthropods; tadpoles feed on frog eggs and mosquito larvae.

reproductive biology

Males call solitarily from bromeliads and tree holes; the call is a series of notes, "boop-boop-boop." Clutches of 48–322 eggs are deposited just above water level on the leaves of bromeliads or on walls of the cavities in trees; only a small percentage of eggs hatch. Hatching tadpoles wriggle into the water and feed on the remaining eggs; the female returns to the site and deposits more eggs, on which tadpoles feed. Tadpoles that are not in crowded containers and that are supplied with sufficient nutritive eggs metamorphose in 60 days.

conservation status

Not threatened.

significance to humans

None known.

European treefrog

Hyla arborea

subfamily

Hylinae

taxonomy

Rana arborea Linnaeus, 1758, Europe. Five subspecies are recognized.

other common names

French: Rainette verte; German: Laubfrosche; Spanish: Ranita de San Antonio; Russian: Obyknovennaya kvaksha.

physical characteristics

Males are 1.3–1.8 in (32–43 mm) long; females are 1.6–2.0 in (40–50 mm) long. A moderately slender treefrog with long legs. The skin on the dorsum is smooth, and the skin on the venter is granular. The dorsum is green or tan with a dark brown stripe from the eye to the groin, bordered above by a narrow white line; the upper lip and venter are creamy white.

distribution

Most of Europe, exclusive of the British Isles and Scandinavia, eastward to the Ural Mountains and northern Turkey. Present on several Mediterranean islands, including Corsica, Crete, Elba, Rhodes, and Sardinia.

habitat

Humid and dry forests.

behavior

Nocturnal and primarily arboreal.

feeding ecology and diet

Feed on a variety of small arthropods.

reproductive biology

After spring rains, males call from low vegetation or shallow water in ponds; the call is a rapid "krak-krak-krak." Females deposit 800–1,000 eggs in small clumps in ponds. The eggs hatch in 12–15 days into free-swimming tadpoles that metamorphose in three or more months.

conservation status

Lower Risk/Near Threatened. The European treefrog is threatened throughout most of its range by habitat destruction and pollution.

significance to humans

None known.

Cope's gray treefrog

Hyla chrysoscelis

subfamily

Hylinae

taxonomy

Hyla femoralis chrysoscelis Cope, 1880, Dallas, Texas, United States.

other common names

None known.

physical characteristics

Males are 1.2–1.8 in (30–45 mm) long; females are 1.6–2.2 in (40–53 mm) long. This is a moderately robust treefrog with lightly tuberculate skin on the dorsum, which is green or gray with darker blotches. There is a white spot below the eye. Hidden surfaces of the hind limbs are yellow; the belly is white.

distribution

Eastern North America; the exact range is unknown, because it overlaps with the morphologically identical gray treefrog (Hyla versicolor), which differs in call and chromosome number.

habitat

Primarily hardwood but also coniferous forest.

behavior

Nocturnal and arboreal.

feeding ecology and diet

Feeds on a variety of small arthropods.

reproductive biology

Breeding takes place after warm spring rains. Males call from bushes and trees bordering ponds; females approach and nudge calling males. Amplexus may last several hours, during which time the female ovulates. In the course of amplexus females carry males to water. The ovarian complement is 485–3,840 eggs, which are laid in small packets of five to 31 eggs attached

to aquatic vegetation. Eggs hatch in four to five days into free-swimming tadpoles that require seven to eight weeks to metamorphose. Females may deposit three decreasingly smaller clutches at intervals of eight to 35 days.

conservation status

Not threatened.

significance to humans

None known.

Hourglass treefrog

Hyla leucophyllata

subfamily

Hylinae

taxonomy

Rana leucophyllata Bereis, 1783, Suriname.

other common names

English: Bereis' treefrog; French: Rainette à bandeau.

physical characteristics

Males are 1.3–1.5 in (33–36 mm) long; females are 1.6–1.8 in (40–44 mm) long. This is a slender treefrog with a truncate snout and smooth skin on the dorsum. The toes are about two-thirds webbed, and there is an extensive axillary membrane. The dorsum is creamy yellow with a brown, hourglass-shaped mark on the back; hidden surfaces of the limbs and the

webbing are orange. The dorsum in some individuals is brown with cream reticulations.

distribution

The Amazon Basin and the Guiana region in South America.

habitat

Lowland tropical rainforest.

behavior

Nocturnal and arboreal.

feeding ecology and diet

Eats mostly moths but also other small insects.

reproductive biology

Males call from vegetation around ponds; the call is a ratcheting primary note followed by two to seven shorter secondary notes. While in axillary amplexus, females deposit clutches of about 600 eggs on vegetation over water. The eggs hatch in five to seven days. Tadpoles drop into water; they are macrophagous and feed on the bottom of shallow ponds.

conservation status

Not threatened.

significance to humans

None known.

Rosenberg's treefrog

Hyla rosenbergi

subfamily

Hylinae

taxonomy

Hyla rosenbergi Boulenger, 1898, Cachabe, Esmeraldas, Ecuador.

other common names

English: Rosenberg's gladiator frog.

physical characteristics

Males are 2.8–3.7 in (77–91 mm) long; females are 3.4–3.8 in (82–93 mm) long. The head is broad and flat. The limbs are long, and the fingers and toes are more than three-fourths webbed. The dorsum is tan with faintly darker mottling; the venter is pale bluish green. Males have an elongated spine on the base of the thumb.

distribution

Pacific lowlands from Costa Rica to Ecuador.

habitat

Humid lowland rainforest.

behavior

Nocturnal and arboreal.

feeding ecology and diet

Eats a variety of arthropods.

reproductive biology

Males excavate shallow basins into which water seeps on mudflats adjacent to ponds or slow-flowing streams. Males call from basins and defend them from other males; the call is a short series of low-pitched notes, "tonk-tonk-tonk." Attracted by the calls, the female enters and inspects the basin; once in amplexus, the female renovates the basin and deposits 1,700–3,000 eggs. Males remain at the basins until the eggs hatch, in 40–66 hours; at subsequent flooding of the basin, the tadpoles enter open water and metamorphose at an age of about 40 days.

conservation status

Not threatened.

significance to humans

None known.

Manaus slender-legged treefrog

Osteocephalus taurinus

subfamily

Hylinae

taxonomy

Osteocephalus taurinus Steindachner, 1862, Manaus, Amazonas, Brazil.

other common names

English: Bony-headed treefrog; French: Ostéocéphale taurin.

physical characteristics

Males are 2.7–3.5 in (66–85 mm) long; females are 3.1–4.2 in (76–104 mm) long. Long-legged, with toes about three-fourths webbed. The dorsal skin in females is smooth and bears spiny tubercles in males. In large individuals, the skin on top of the head is co-ossified with underlying bones, which form a pair of longitudinal ridges on the top of the head. The dorsum is tan to reddish brown, with brown irregular markings on the back and bars on the limbs; the venter is cream with brown spots or mottling on the chest. The iris is bronze with radiating black lines. Males have paired lateral vocal sacs.

distribution

The Amazon Basin and Guianan region of South America.

habitat

Humid lowland rainforest.

behavior

Nocturnal and arboreal.

feeding ecology and diet

Eats a variety of arthropods, especially orthopterans.

reproductive biology

After the initial heavy rains of the season, males congregate at ponds and mostly call while floating on the surface of the water; the call is a loud "boop-boop-boop," followed or not by a "worrr." Females deposit 500–600 small pigmented eggs as a surface film on the water. The eggs hatch in about 24 hours; the free-swimming tadpoles require about 86 days to reach metamorphosis.

conservation status

Not threatened.

significance to humans

Some indigenous people eat this species.

Cuban treefrog

Osteopilus septentrionalis

subfamily

Hylinae

taxonomy

Hyla septentrionalis Duméril and Bibron, 1841, Cuba.

other common names

German: Kuba-Laubfrosch; Spanish: Rana platanera.

physical characteristics

Males are 2.5–3.6 in (60–89 mm) long; females are 3.7–5.7 in (90–140 mm) long. The head is broad and flat; the skin is coossified with the skull in large individuals. The dorsum has scattered tubercles, and the venter is granular. The toes are about two-thirds webbed. The dorsum is gray to olive green, with bold darker mottling or elongated blotches; the venter is creamy white.

distribution

Cuba, the Cayman Islands, and the Bahamas. They have been introduced into Puerto Rico, various islands in the Lesser Antilles, and Florida in the United States.

habitat

Mesic and dry forest.

behavior

These frogs are nocturnal and arboreal. Diurnal retreats include banana plants, burrows, cisterns, and secluded areas in buildings; they are tolerant of brackish water.

feeding ecology and diet

Large individuals have a voracious appetite and feed on a variety of insects, small crustaceans, and frogs.

reproductive biology

Males call from vegetation near water and from vertical walls adjacent to pools of rainwater; the call consists of a series of loud, low-pitched notes. Eggs are deposited as a surface film on water and hatch in 27–30 hours into free-swimming tadpoles.

conservation status

Not threatened.

significance to humans

None known.

Hartweg's spike-thumbed frog

Plectrohyla hartwegi

subfamily

Hylinae

taxonomy

Plectrohyla hartwegi Duellman, 1968, Barrejonel, Chiápas, Mexico.

other common names

Spanish: Ranita de dedos delgados.

physical characteristics

Males are 2.2–2.9 in (54–72 mm) long; females are 2.2–3.1 in (54–77 mm) long. The body is robust, with finely tuberculate skin and a short snout. The arms are robust in males, with a bifid spine at the base of the thumb; the toes are about four-fifths webbed. The dorsum is olive tan to green, and the venter is pale gray. The anterior and posterior surfaces of the thighs are mottled boldly with pale cream and black or dark green.

distribution

Moderate to high elevations of the Pacific slopes of Chiápas, Mexico, and the Atlantic slopes of Guatemala and northwestern Honduras.

habitat

Montane cloud forest.

behavior

Active at night on rocks at the edges of streams and in trees bordering streams.

feeding ecology and diet

Eats a variety of arthropods.

reproductive biology

Males are not known to vocalize. Females deposit 191–352 eggs in streams. Tadpoles have large, ventral mouths and adhere to stones in pools in streams.

conservation status

Not threatened.

significance to humans

None known.

Chorus frog

Pseudacris triseriata

subfamily

Hylinae

taxonomy

Hyla triseriata Wied, 1839, Mount Vernon, Ohio River, Indiana, United States.

other common names

French: Rainette faux criquet, rainette faux-grillon de l'Ouest.

physical characteristics

Males are 0.8–1.2 in (19–29 mm) long; females are 1.2–1.5 in (29–37 mm) long. The skin on the dorsum is slightly tubercular, and on the venter it is granular. The snout is acutely rounded. The toes are about one-third webbed. The dorsum is grayish tan, with brown mid-dorsal and dorsolateral stripes or rows of spots. There is a broad dark brown or black stripe from the snout through the eye and tympanum to the groin; the venter is white.

distribution

Eastern North America.

habitat

Grassland, pastures, cropland, and moist forest.

behavior

Nocturnal and terrestrial.

feeding ecology and diet

Eats small arthropods, including beetles, grubs, ants, and spiders.

reproductive biology

Breeding occurs after the first spring rains. Males call from grasses in the water or at the edge of water in ponds, marshes, and roadside ditches. The call consists of a vibrant, pulsed "crreeck." Females deposit 100–1,500 eggs in small clutches of five to 300 eggs attached to vegetation in shallow water. Eggs require about two weeks to hatch into small, free-swimming tadpoles that metamorphose in about two months.

conservation status

Not threatened.

significance to humans

None known.

Amazonian skittering frog

Scarthyla goinorum

subfamily

Hylinae

taxonomy

Hyla goinorum Bokermann, 1962, Tarauacá, Acre, Brazil.

other common names

None known.

physical characteristics

Males are 0.6–0.8 in (15–20 mm) long; females are 0.7–0,9 in (18–23 mm) long. Slender body with a pointed snout and long limbs with fully webbed toes. The dorsum is green with brown and white lateral stripes; the venter is white.

distribution

Upper Amazon Basin from southern Colombia to northeastern Bolivia.

habitat

Swampy regions in lowland tropical rainforest.

behavior

Nocturnal and arboreal; they perch on leaves just above the surface of the water and are capable of skittering across the surface.

feeding ecology and diet

Eats a variety of small arthropods; spiders make up more than 50% of their diet.

reproductive biology

Males call from low vegetation above water; the call consists of eight to 10 short, whistle-like notes. Clutches of 130–202 small, pigmented eggs are deposited in ponds. Elongate tadpoles have muscular tails with low fins. Macrophagous tadpoles swim just below the surface of the water and can propel themselves out of water for distances of 8–12 in (20–30 cm).

conservation status

Not threatened.

significance to humans

None known.

Yucatecan shovel-headed treefrog

Triprion petasatus

subfamily

Hylinae

taxonomy

Pharyngodon petasatus Cope, 1865, Cenote Tamanché, Yucatán, Mexico.

other common names

Spanish: Ranita de casco yucateca.

physical characteristics

Males are 2–2.5 in (48–61 mm) long; females are 2.6–3 in (65–75 mm) long. The head is casque-shaped, with a large, upturned prenasal bone and expanded maxillaries forming a broad labial shelf. The dorsum is olive green or tan with dark brown markings. The belly is white, and the undersides of the limbs are tan.

distribution

Yucatán Peninsula of Mexico, northern Guatemala, and Belize; a disjunct population exists in northwestern Honduras.

habitat

Semiarid scrub forest and savannas.

behavior

A nocturnal species, found on the ground, bushes, and low trees.

feeding ecology and diet

Eats a variety of small arthropods and small frogs.

reproductive biology

An explosive breeder after heavy rains. Males call from trees, bushes, and ground around temporary pools; the call consists of quickly repeated, low-pitched notes resembling the quacking of a duck. Eggs are laid in clumps in water, where they hatch into free-swimming tadpoles.

conservation status

Not threatened.

significance to humans

None known.

Water-holding frog

Cyclorana platycephala

subfamily

Pelodryadinae

taxonomy

Chiroleptis platycephalus Günther, 1873, Fort Bourke, New South Wales, Australia.

other common names

None known.

physical characteristics

Males are 1.7–2.6 in (42–64 mm) long; females are 2.0–2.9 in (50–72 mm) long. A robust frog with a flat head, small eyes, muscular limbs, a spadelike tubercle on the foot, and extensively webbed toes. The dorsum is dull gray, brown, or green with irregular darker blotches; the venter is dull white.

distribution

Found discontinuously in the interior of Australia.

habitat

Dry grassland and desert.

behavior

Nocturnal and terrestrial. Using their hind feet, the frogs burrow into soil and shed multiple layers of skin that form a nearly impermeable cocoon, to prevent water loss during months of estivation.

feeding ecology and diet

Eats a variety of arthropods.

reproductive biology

After rains create temporary ponds, males congregate and call; the call is a long snoring sound, "maw-w-w-w-maw-w-w-w." Eggs are laid in clumps in shallow water; free-swimming tadpoles metamorphose in as few as 30 days.

conservation status

Not threatened.

significance to humans

Aborigines dig up estivating frogs and squeeze water from them.

Green treefrog

Litoria caerulea

subfamily

Pelodryadinae

taxonomy

Rana caerulea White, 1790, New South Wales, Australia. Some authors place this species in the genus Pelodryas.

other common names

English: White's treefrog.

physical characteristics

Males are 2.7–3.1 in (66–77 mm) long; females are 2.9–4.5 in (70–110 mm) long. The green treefrog is a robust-bodied tree-frog with large, diffuse glands on the back of the head and extensively webbed toes. The dorsum is green; the venter is white.

distribution

Found from northern and eastern Australia to southern New South Wales and in southern New Guinea. It has been introduced into New Zealand.

habitat

Dry and humid forests.

behavior

Nocturnal and arboreal.

feeding ecology and diet

Eats a variety of arthropods, other frogs, and small mammals.

reproductive biology

After rains males call from trees, rocks, and ground near swamps and slow-moving streams; the call is a continuously repeated "crawk." Clutches of 200–2,000 eggs are deposited in still water from November to February. Free-swimming tadpoles metamorphose in about six weeks.

conservation status

Not threatened.

significance to humans

Caerulin, a drug used to control hypertension, was discovered in the skin secretions of this species. Now the compounds have been synthesized, and the drug is produced artificially. This is a common species in the pet trade.

Rocket frog

Litoria nasuta

subfamily

Pelodryadinae

taxonomy

Pelodytes nasutus Gray, 1842, Port Essington, Northern Territory, Australia.

other common names

None known.

physical characteristics

Males are 1.3–1.8 in (33–45 mm) long; females are 1.5–2.3 in (36–55 mm) long. A streamlined frog with extremely long legs and a pointed snout. The dorsum is colored in shades of brown, with darker longitudinal skin folds or rows of pustules; the venter is white.

distribution

Found in coastal and adjacent areas of northern and eastern Australia, from northern Western Australia to central New South Wales; they also live in southern New Guinea.

habitat

Dry and humid forests.

behavior

Nocturnal and terrestrial and capable of making a series of long leaps.

feeding ecology and diet

Feeds on a variety of arthropods.

reproductive biology

Males call from the edges of ponds in November through February; the call is a series of notes, "wick-wick-wick-wick." Batches of 50–100 eggs are laid as a surface film on water; free-swimming tadpoles metamorphose in about one month.

conservation status

Not threatened.

significance to humans

None known.

Red-eyed treefrog

Agalychnis callidryas

subfamily

Phyllomedusinae

taxonomy

Hyla callidryas Cope, 1862, Darién, Panama.

other common names

English: Red-eyed leaf frog; Spanish: Ninfa de bosque, rana borracha, rana-de àrbol ojos rojos.

physical characteristics

Males are 1.6–2.5 in (39–59 mm) long; females are 2.2–2.9 in (51–71 mm) long. Slender, long-legged treefrog with a green dorsum, blue flanks with white vertical bars, a creamy white venter, vertical pupil, bright red iris, and lower eyelid reticulated with white or pale yellow.

distribution

Found at elevations from sea level to 3,100 ft (960 m), from southeastern Mexico to extreme northwestern Colombia.

habitat

Humid lowland rainforest.

behavior

The frog is nocturnal and arboreal; by day, the limbs are tucked closely against the body, and they sleep on the undersides of leaves.

feeding ecology and diet

Eats a variety of small arthropods, especially orthopterns.

reproductive biology

Males call from branches and leaves of trees above ponds in the rainy season; the call is a soft single or double note, "cluck." Females approach calling males; once in amplexus, the female descends to the pond, where she absorbs water and then climbs to a leaf above the water. Clutches of 11–78 eggs are deposited on the leaf, which usually is folded around the egg clutch. Females deposit only part of their ovarian complement in one clutch. Hatchling tadpoles drop into the water. Tadpoles are mid-water filter feeders and orient themselves in a head-up position.

conservation status

Not threatened.

significance to humans

This frog, which is common in the pet trade, has become the "poster frog" for many conservation organizations.

White-lined treefrog

Phyllomedusa vaillanti

subfamily

Phyllomedusinae

taxonomy

Phyllomedusa vaillanti Boulenger, 1882, Santarem, Pará, Brazil.

other common names

French: Phylloméduse de Vaillant.

physical characteristics

Males are 2.0–2.4 in (50–58 mm) long; females are 1.8–2.4 in (68–84 mm) long. A large treefrog with a truncate snout and a pair of elevated, longitudinal parotoid glands posterior to the eye and extending to the mid-body. The innermost fingers and toes are longer than the adjacent ones; webbing is absent. The dorsum and side of the head are green, with a row of white granules along the angle of the parotoid gland; the flanks are green above and reddish brown below, with row of elliptical cream or orange spots. The venter is brownish gray, with a pair of cream spots on the throat and a large green spot on the chest. The pupil is vertical, with a pale gray iris.

distribution

Amazon Basin and Guiana region of South America.

habitat

Lowland tropical rainforest.

behavior

Nocturnal and arboreal; the frog methodically walks on branches of trees and bushes.

feeding ecology and diet

Feeds on a variety of arthropods.

reproductive biology

After rains males call from vegetation above permanent ponds; the call is a short, harsh "cluck." Females approach males. Once in amplexus, the female carries the male to a pond, where she absorbs water, and then to a large leaf, where clutches of 415–645 eggs are deposited. Eggs hatch in about four days, and tadpoles drop into the water, where they are free-swimming, usually in schools of more than 50 individuals. The tadpoles are midwater filter feeders that orient themselves in a head-up position.

conservation status

Not threatened.

significance to humans

None known.

Paradox frog

Pseudis paradoxa

subfamily

Pseudinae

taxonomy

Rana paradoxa Linnaeus, 1758, Suriname. Six subspecies are recognized.

other common names

English: Paradoxical frog; French: Grenouille paradoxale; Spanish: Rana boyadera.

physical characteristics

Males are 1.6–2.7 in (38–65 mm) long; females are 1.7–3.2 in (40–65 mm) long. The snout is acutely rounded, and the eyes are large and protuberant dorsally. The limbs are long and muscular, with fully webbed toes. The dorsum is greenish tan; the venter is white. The posterior surfaces of the thighs are cream with brown longitudinal stripes.

distribution

Distributed disjunctly in South America—the lower Río Magdalena Valley in Colombia, the Llanos of Colombia and Venezuela, Trinidad, central and southern Brazil, southern Peru, eastern Bolivia, Paraguay, and northern Argentina.

habitat

Marshes and permanent ponds in savannas and open forest in tropical lowlands.

behavior

Nocturnal and aquatic, but during the breeding season males call by day and night; they float in water with only their eyes above the surface.

feeding ecology and diet

Feeds on a variety of aquatic arthropods and small frogs.

reproductive biology

Breeding takes place in water. Females are attracted to males by their call, a single loud croak. Frothy masses of eggs are laid amidst aquatic vegetation. Free-swimming tadpoles grow to total lengths of 11 in (270 mm).

conservation status

Not threatened.

significance to humans

Some indigenous peoples eat the tadpoles.

Resources

Books

Barker, John, Gordon Grigg, and Michael J. Tyler. A Field Guide to Australian Frogs. Chipping Norton, Australia: Surrey Beatty and Sons, 1995.

Duellman, William E. Hylid Frogs of Middle America. Ithaca, NY: Society for the Study of Amphibians and Reptiles, 2001.

Lescure, Jean, and Christian Marty. Atlas des Amphibiens de Guyane. Paris: Muséum National d'Histoire Naturelle, 2001.

Periodicals

Duellman, William E. "The Biology of an Equatorial Herpetofauna in Amazonian Ecuador." Miscellaneous Publications, Museum of Natural History of the University of Kansas 65 (1978): 1–352.

Rodríguez, Lily O., and William E. Duellman. "Guide to the Frogs of the Iquitos Region, Amazonian Peru." Special Publications, Museum of Natural History of the University of Kansas 22 (1994): 1–80.

Trueb, Linda. "Evolutionary Relationships of Casque-headed Tree Frogs with Co-ossifed Skulls (Family Hylidae)." Miscellaneous Publications, Museum of Natural History of the University of Kansas 18, no. 7 (1970): 547–716.

William E. Duellman, PhD