Mainly active during the day, Darwin's frog frequently basks in sunlight, while camouflaged amongst the leaf litter. This species mainly feeds upon insects and other small invertebrates, which it catches by remaining motionless and waiting for the unsuspecting animal to come near, before lunging forwards and devouring its prey. When threatened Darwin's frog will play dead, rolling onto its back and lying motionless, or, more dramatically, it will leap into a stream, and float in the water on its back, again feigning death (2). The male Darwin's frog produces vocalisations throughout the year, but mainly during the breeding season, which occurs from November to March. After encountering a prospective mate, the male leads the female to a sheltered site where courtship and egg-laying take place. The female deposits a clutch of around 40 eggs, each four millimetres wide, in the leaf litter, which are fertilised by the male. The female then departs, but the male remains with the eggs, guarding them while they develop (2). After around 20 days, when the tadpoles begin to wriggle within the eggs, the male uses its tongue to pick up the eggs, and manoeuvres them through the slits in its mouth into the vocal sac (2) (4). Here, the tadpoles hatch from the eggs and remain while metamorphosis takes place. While in the sac, the tadpoles are sustained by the remainders of the yolk from the egg, as well as nutrient-rich secretions produced by the adult (2). Once development has progressed to the point where the young are around 1 cm long and the tail has become reduced to a small stump, they move out of the vocal sac and are released by the male out of the mouth (4). As many as 19 tadpoles may be brooded by a single male, causing the internal organ's to distort to accommodate the mass of offspring, but returning to normal after the froglets are released (2) (4).

Rhinoderma darwinii is a relatively small frog (males 22-28 mm, females 25-31 mm). It has a pronounced, fleshy proboscis, which gives the head a triangular appearance. Tympana are indistinct. The skull is weakly ossified. Forelimbs and hindlimbs are relatively long and slender. Webbing is moderate between toes I and II, and II and III, less developed between toes III and IV, and lacking between toes IV and V. A metatarsal tubercle is present but not as large as that of the related species Rhinoderma rufum. Brooding males have enlarged vocal sacs, due to the sacs containing developing embryos. Coloration is highly variable, with the dorsum being either uniform brown (tan, brown, or reddish brown), uniform green (pale or dark), or some combination of brown and/or green with variable patterns. The underside is black and white, with large blotches (Crump 2003; Duellman and Trueb 1986).

Larvae lack external gills, a spiracle, a beak, and denticles, indicating they are not free-living. Larvae also lack interdigital membranes and digital tubercles on the hind legs. The caudal fin is poorly developed (Jorquera et al. 1972).

Discovered by Charles Darwin in the thick, gloomy forests of southern-central Chile, Darwin's frog possesses a distinctive appearance and an unusual biology (2) (3). The head of this species has a triangular appearance due to the presence of a pronounced, fleshy proboscis that projects from the tip of the snout. The colouration of the warty upperparts is variable, with individuals exhibiting various shades of brown, green or a mixture of the two. By contrast the underparts are invariably black and white with large blotches (2). The male Darwin's frog possesses a large vocal sac, extending from beneath the throat, over the belly, to the groin. Rather than enabling the male to produce a booming call, this sac has an unusual role in brooding offspring, and the call is, in fact, small and bell-like (4).

This species is endemic to the austral forest of Chile and Argentina. Historically, it was distributed in Chile from Concepción Province to Palena Province. In Argentina, it is known from Neuquén and Río Negro provinces. It has an altitudinal range of 50-1,100 m asl.

Chile and Argentina (Crump 1999).

Biogeographic Regions: neotropical (Native )

Magallanes

Endemic to the austral forest of Chile and Argentina. Historically, it was distributed in Chile from Concepcion Province to Palena Province. In Argentina, it is known from Neuquén and Río Negro provinces. It has an altitudinal range of 50-1,100m asl.

This species occurs in central and southern Chile, and Argentina. In Chile it occurs from the province of Maule south to the province of Aisen, up to 1500 m in elevation. In adjacent Argentina it is found in the provinces of Neuquen and Rio Negro (Crump 2003). Rhinoderma darwinii is found in temperate and austral forests, along cool (5-21 degrees C) and wet stream banks of slowly moving streams (Penna and Veloso 1990; Cooper et al. 1978; Crump 2003), as well as forest bogs (IUCN 2006).

Darwin's frog occupies the austral forest of southern-central Chile and Argentina. This species is most abundant on the Chiloé Archipelago, Chile, and scarce within Argentina, where it is only known from the province of Neuquen and Río Negro. It can be found between altitudes of 50 to 1,500 metres above sea-level (1) (2).

Length: 2.5-3.5cm

Rhinoderma darwinii has a triangular shaped head with a long, and somewhat pointy nasal extension. Color ranges from brown to bright green depending on the substrate R. darwinii is imitating. The ventrum is more brilliantly colored with a black background and big white spots as well as smaller yellow and orange spots. Its skin is basically smooth with only a few wart glands (Gallardo 1999).

Range length: 2.5 to 3.5 cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Adult morphology Size of about 25-30 mm. Head flattened, triangular as seen from above; snout pointed, ended by a cylindrical appendix and clearly protruding on lower jaw. Interocular distance larger than than upper eyelid but smaller than the internarial interval. Nostrils closer to the tip of snout than to the eye. Tympanum evident, its diameter being about 4/5 of the eye diameter. Tongue subcircular, free behind, Fingers free, or with a very smaIl fringe; toes 1/3 webbed. Rate of the finger lengths: I-II-IV-III. Metacarpal and subarticular tubercles very faint; inner metatarsal tubercle small, rounded; outer metatarsal tubercle not evident, No tarsal fold present. Foreleg and hindleg slender: when hindeg is adpressed, heel reaches the tympanum. Skin dorsally smooth, with 1ongitudinaI glandular ridges on the sides. Ventrally srnooh, slightly granular in the femoral region. A small dermal appendix on the tibio-tarsal articulation. Dorsal color green or brownish, faintIy dark spotted, with a wide range of individual variation. Ventrally black, scattered with bright white spots; throat grayish, mottled with dark.

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

R. darwinii is found in temperate forests and rainforests (Cannatella 1995, Gallardo 1999).

Habitat Regions: temperate

Terrestrial Biomes: forest ; rainforest

Generally found on land (4), Darwin's frog inhabits moist leaf-litter, often along the banks of slow moving streams and within boggy areas, in cool, temperate forests (2).

R. darwinii is insectivorous (Gallardo 1999).

Animal Foods: insects; terrestrial non-insect arthropods

Primary Diet: carnivore (Insectivore , Eats non-insect arthropods)

Female Rhinoderma darwinii lay their eggs on moist soil and when the eggs hatch, the males "swallow" the tadpoles and put them in their specialized vocal sacs. The tadpoles stay there through metamorphosis, about 6 weeks, and then are released in a series of convulsive movements as miniature frogs (Cogger and Zweifel 1998, Gallardo 1999)

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous

The following is a representative barcode sequence, the centroid of all available sequences for this species. 

 
There is 1 barcode sequence available from BOLD and GenBank.   Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen.  Other sequences that do not yet meet barcode criteria may also be available.
 

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Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Species: 1
Species With Barcodes: 1

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

IUCN Red List of Threatened Species: vulnerable

VU. Vulnerable.

The Darwin's frog is classified as Vulnerable (VU) on the IUCN Red List (1).

Population

Population Trend

During the colder months, Rhinoderma darwinii shelters under cover of logs or moss (Crump 2003). This species is mainly diurnal, and often basks in sunlight (Crump 2003). Despite being primarily diurnal, males call at night as well as during the day (Crump 2003). Vocalization is most prevalent throughout the breeding season (November through March; Crump 2003). The call is a rapid "piiiip, piiiiip, piiiiip, piiiiip" (Crump 2003). Individuals were observed giving an average of 2.5 calls/minute, at an average frequency of 2550 Hz (Penna and Veloso 1990). Calls are composed of 2 to 3 notes, with the total call lasting between 580 and 1700 msec (Penna and Veloso 1990).

In captivity, and probably also in the wild, the male leads the female to a sheltered site, where courtship is conducted. After some time, the female moves underneath the male. Amplexus is loose, rather than the male gripping the female tightly (Crump 2003).

This species is a direct developer, without free-living larvae (Jorquera et al. 1982), and has a very unusual form of parental care. In each terrestrial clutch, deposited in the leaf-litter, there are about 40 large (4 mm), unpigmented eggs (Duellman and Trueb 1986; Jorquera et al. 1972). Clutch size in the far south of the range may be smaller (3-7 eggs; Crump 2003). After the male has fertilized the eggs, he remains in close proximity. When the larvae have reached the stage where they can wriggle inside the eggs (about 20 days post-oviposition), the male takes the embryos up into his vocal sac, where they hatch into tadpoles about 3 days later (Cei 1962; Jorquera et al. 1982). As many as 19 embryos have been found within a male's vocal sac (Busse 1970); it is not known what the maximum is.

After hatching, larval development and metamorphosis take place within the vocal sac of the male parent (Jorquera et al. 1982). This post-hatching period of development lasts for about 50-70 days (Jorquera et al. 1982; Crump 2003). The male not only shelters the tadpoles but nourishes them via viscous secretions within the vocal sac (Goicoechea et al. 1986). Within the vocal sac, the tadpole absorbs paternal nutrition via the skin, and yolk from the egg (Goicoechea et al. 1986). By stage 11, yolk is depleted (Jorquera et al. 1982). In addition, the intestinal epithelium has differentiated by this stage, so that the tadpole is now also able to ingest parental nutritious secretions via the mouth and absorb it via the digestive system (Goicochea et al. 1986). At the end of metamorphosis the froglets move from the male's vocal sac into the mouth, and emerge from the mouth (Jorquera et al. 1982).

Only one other species of frog (Rhinoderma rufum) broods embryos within the male's vocal sac. Although this species has not been been experimentally confirmed to transport substances from the paternal circulation to the larvae, it has the same specialized secretory structures within the vocal sac epithelium as does R. darwinii. However, in Rhinoderma rufum the embryos are retained for a much shorter time within the vocal sacs, and complete development as free-living larvae, outside the male. In Rhinoderma rufum, the larvae develop keratinized jaws (unlike in R. darwinii). In addition, the intestinal epithelium matures much earlier in development (stage 2 in R. rufum vs. stage 11 in R. darwinii). The larvae of R. rufum are expelled from the male's vocal sac at stage 3 to feed and finish development in an aquatic environment, unlike those of R. darwinii, which complete development wholly within the male's vocal sac (Jorquera et al. 1982).

This frog has the unusual defensive strategy of playing dead when threatened; it rolls over on its back and remains motionless. If it is near a stream when frightened, it may jump into the stream and float in the water on its back (Crump 2003).

Rhinoderma darwinii consumes insects and other small invertebrates, using a sit-and-wait predation strategy (Crump 2003).

Major Threats

Most of the range is within Chile. Rhinoderma darwinii is most abundant on the archipelago, where there is little habitat disturbance, and in some southern Chilean localities. In other parts of the range within Chile, populations are declining or have vanished entirely, in some cases due to deforestation or replacement of native trees with non-native pine or eucalyptus, but in other cases from unknown causes. This species is rare in Argentina (IUCN 2006).

In recent years, Darwin's frog has undergone a worrying decline throughout its range, with some populations in Chile disappearing entirely (1). While in some areas, particularly in the northern part of this species' range, the decline can be attributed to deforestation and replacement of native trees with exotic pine or eucalyptus species, in other regions, which are more remote or protected, the cause is unknown (2). It may, however, be linked to global changes in climate and increased ultraviolet radiation, which are believed to be contributing to the ongoing worldwide decline in amphibians (2) (5).

Conservation Actions

Darwin's frog is located in several protected areas throughout its range, which are helping to preserve its dwindling habitat. Nevertheless, there is a need for improved maintenance of existing sites, as well as expansion of the protected area network, especially in the more heavily exploited northern parts of this species' range. In order to understand the causes of the unexplained decline of Darwin's frog in apparently suitable areas of habitat, the population must be closely monitored. This should then inform the development of a conservation strategy for this imperilled species (1).

It can be found in open areas around human habitation, primarily in swampy areas or near slowly running streams (Crump 2003).