The Darwin's frog, also known as Darwin's little frog or toad, is a small amphibian native to South America that has become known worldwide after its mention in Darwin's writings. In their natural habitat, they can be difficult to spot, as they are usually easily camouflaged thanks to their leaf-like appearance.
Origin of Darwin's Frog
Darwin's frog (Rhinoderma darwinii) is a small amphibian endemic to Argentina and Chile, which lives mainly in the temperate forests of the Patagonian region. It adapts optimally to humid and arboreal regions with altitudes between 15 and 1,800 meters above sea level, showing a predilection for mature native forests with a more complex structure.
In Argentina, its population is concentrated only in the border regions with Chile, being possible to observe its presence in the Nahuel Huapi and Lanín National Parks, located between the provinces of Río Negro and Neuquén [1]Already in Chile, the Darwin's frog is distributed from the city of Concepción to Aysén, located in Regions VIII and XI, respectively[2]
Its name is a tribute to the great English naturalist and biologist, Charles Darwin, who was the first to portray this species during his famous trips to South America, devoting some lines to it from his book ' Viaje del Beagle '.
Characteristics of Darwin's Frog
Darwin's frog is characterized by a rounded body, triangular head with a pointed snout and a cylindrical nasal appendage. Females are usually slightly larger, measuring between 2.5 and 3.5 cm in adulthood, while males hardly exceed 2.8 cm. Likewise, the size of these little frogs can vary depending on the climate of their habitat, with the largest specimens usually living in regions with the most marked seasonality.
His limbs are relatively long and thin compared to the rest of his body. The front legs do not have palms between the fingers, while in the hind legs, palms can be seen only in the first three fingers. The skin on its back is slightly grainy and has lateral folds, and can show variable shades from brighter greens to shades of coffee brown. Already in the ventral zone, the black background with white spots predominates, this pattern that could characterize an aposomatic coloration to alert and scare off predators[3]
In Chile, there is another species of frog, called Rhinoderma rufum and popularly known as Chilean Darwin's toad, which is very similar to Darwin's frog. Unfortunately, this small Chilean frog is considered extinct, since it has not been officially recorded in its natural habitat since 1978.
Darwin's Frog Behavior
Thanks to the shape and coloration of its body, Darwin's frog can camouflage itself relatively easily among the leaves of the immense forests Patagonian, thus managing to dissuade many of their predators. Even so, this small amphibian has several predators in its natural habitat, such as rodents, birds and snakes. Also, when its camouflage technique cannot be used or is not efficient, and the frog finds itself faced with a predator, it often jumps back and drops onto its back, evidencing the peculiar pattern of its belly. This behavior is one of the pieces of evidence that leads experts to estimate that it is a aposomal coloration to alert and scare off predators.
Regarding its diet, it is a carnivorous animal, whose diet is mainly based on the consumption of insects, snails, spiders, worms and small invertebrates in general. In their hunting habits, Darwin's frogs strategically use their long sticky tongue to catch their prey, while remaining "disguised" among the leaves of the native forests or swampy areas.
One of the most curious aspects of the behavior of Darwin's frog is its song, which registers a very high pitched pitch, resulting similar to the song of some birds. To human ears, this sound can resemble the whistle emitted by cowboys in the fields, which is why this beautiful and tiny frog is also known as " cowboy toad" in its countries of origin.
Darwin's frog reproduction
Darwin's frog reproduction is unique among amphibians, maintaining a peculiar form of incubation called "neomaly". During the breeding season, males and females meet and perform a kind of brief and soft nuptial hug called amplexus. At the end of this embrace, the female deposits on the ground between 3 and 30 small eggs, which usually do not exceed 4 mm in diameter. About 15 days after the amplexus, the embryos already present their first movements, and it is then that the male introduces them into his mouth so that they later reach the vocal sac located in his throat.
Inside the vocal sac of the male, Darwin's froglets complete their larval development usually during the spring or fall. After about six to eight weeks, the tiny pups are "expelled" from their parent's vocal sac through an opening under their tongue. From this moment on, his body is ready to jump and adapt to life on earth, just like his parents[4]
The reproductive seasons of Darwin's frogs are irregular, and can occur throughout the year However, the peculiar type The incubation process they carry out is usually favored by the hot summer weather, which is why it usually happens between December and March.
Conservation status of the Darwin's frog
Wondering if Darwin's frog is in danger of extinction? Currently, the Darwin's frog is a threatened species, being classified as "endangered" according to the Red List of Threatened Species , carried out by the IUCN (International Union for Conservation of Nature)[5]
The rapid and worrying decline in its population is mainly due to the fact that, for several years, native forests have been degraded to make way for agricultural and livestock areas. In addition to deforestation, Darwin's frogs appear to be particularly susceptible to an infectious pathology called chytridiomycosis, which affects several amphibian species and is caused by a fungus of the genus Chytridiomycota.
The " Binational Strategy for the Conservation of Darwin's Frogs ", is an important initiative that, as its name indicates, tries to stop the advance on the habitat of the Darwin's frog, prevent its hunting or capture and raise awareness of its essential role in the balance of South American ecosystems.
