5 minutes
The harlequin frog stands out for its fantastic coloration, which announces the presence of poisonous toxins on its skin. Want to know more about it?
Written and verified by the biologist Francisco Morata Carramolino.
Last update: 21 December, 2022
Small, beautiful, and increasingly rare, harlequin frogs are a genus of anurans from southern and Central American natural environments. Despite being of significant cultural importance, many species of harlequin frog are disappearing from the planet.
In this space, we’ll talk about a specific type of harlequin frog, the so-called variable harlequin (Atelopus varius). Most of the populations of these animals have disappeared, but there may still be hope for the species. If you want to learn more about its habitat, main characteristics, and conservation problems, keep reading!
Harlequin frog habitat
Originally, the known distribution range for Atelopus varius was the mountain ranges that run through Costa Rica and Panama, in Central America. These amphibians appeared on both the Atlantic and Pacific slopes of these mountains, but today it’s impossible to find them in most of their original territory.
In 2008, the harlequin frog had disappeared from practically all of its Costa Rican range, except for two unique locations. After that, some were found again in 9 small points. Panamanian populations have also become extinct from much of their former range. Today, they only appear in 6 locations near the center of the country.
These anurans are mainly terrestrial. They inhabit humid tropical forests, both lowland and mountain. They can be found from 16 to 2000 meters above sea level. In these ecosystems, frogs are associated with rocky, fast-water streams.
Harlequin frogs are slow and diurnal. During the day, they’re found on the banks of streams or on rocks. At night, they take refuge in crevices or under vegetation.
Physical characteristics
Harlequin frogs, which are also called “clown frogs” or “painted frogs” are very small. Males are smaller than females, with a body length of 2.5 to 4 centimeters (1 – 1.5 inches). The females, on the other hand, reach between 3 and 6 centimeters (1.2 – 2.3 inches) in total size.
Along with its size, the harlequin frog’s proportions and coloration give it its iconic look. These amphibians are slender and bony, with a relatively rectangular body. The four legs are very thin and long and their heads small and pointed, with two large, round, bulging eyes.
The coloration is highly variable, as you can guess from the name of the animal. It consists of two main parts: the first is a striking color, which can be from orange to yellow or green, as well as their combinations. The second hue consists of a series of dark brown or black markings.
These brands are also very different between individuals. In some, they only involve a series of points that occupy a tiny portion of the body surface. In others, the marks form a series of solid spots of color that occupy most of the body.
Of course, many specimens are found between these two cases. In addition, the throat and belly may appear bright red, and the groin is usually also green or blue-green.
The striking colors of this species are no coincidence. A. varius contains poisonous compounds such as bufadienolide and tetrodotoxin in the skin. These substances serve as a defense against predators, while the coloration is a clear warning sign of toxicity for potential attackers. This is a clear example of aposematism.
Conservation status of the harlequin frog
The situation of this species, as happens with other members of the genus Atelopus and many other species of amphibians, is not at all good. Between the 1980s and 1990s, its total population declined by 80%. From this point to the present, it’s estimated that the remaining population could have lost another 80% of its members. Let’s look at some of the triggers.
Chytridiomycosis
Behind the massive disappearance of this species – which was quite common before – is the chytrid fungus Batrachochytrium dendrobatidis. This fungal microorganism produces a skin disease in amphibians called chytridiomycosis.
Distributed throughout the world by humans, chytrid has become a deadly killer. This parasite is responsible for eliminating countless amphibians and extinguishing entire species, in a veritable pandemic that continues to expand today. It’s estimated that, so far, chytrid has been a direct trigger for the disappearance of 200 species of amphibians.
The fungus attacks, colonizes, develops, and feeds on the moist skin of amphibians. For other animals, this wouldn’t be such a serious problem, but frogs and toads use the skin for essential functions of their lives. Through the external tissue, they’re able to breathe, absorb water and maintain osmotic balance.
Consequently, most frogs, toads, salamanders, or newts affected by this disease end up dying quickly. Additionally, the fungus is highly contagious, contributing to the severity of the pandemic, which has been described as the worst pathogen in history.
Other threats
Besides chytridiomycosis, other common suspects have contributed to the decline of the harlequin frog. One of them is the destruction of their forest habitats by the agricultural, electrical, and mining industries. The introduction of invasive species has also had a negative effect, as well as the capture of specimens for the illegal trade in exotic pets.
Based on all this evidence, the International Union for Conservation of Nature has classified A. varius as “Critically Endangered”, the most serious level of threat.
A light at the end of the tunnel
The situation of this species remains extremely fragile, but a recent study sheds some hope about its future. Voyles and colleagues indicate that some of the populations destroyed by the fungus may have developed resistance to the disease and are slowly beginning to recover.
However, long-lasting and insensitive conservation efforts are badly needed today to save this species from extinction. We have caused this situation and it’s in our hands to remedy it.
