Six Colorful Frogs: Interesting Facts About Attractive Amphibians
Frogs are interesting amphibians. Their skin color often helps to camouflage them. Some frogs have bodies with vivid colors that attract attention, however. I describe six of these colorful amphibians in this article.
Blue and strawberry poison dart frogs and the golden poison frog are toxic, as their names suggest. The tomato frog also produces a toxin. The lovely Malagasy rainbow frog is not poisonous, and neither is the emerald glass frog. The skin on the undersurface of the latter animal is translucent. This enables a viewer to see its internal organs.
Frogs belong to the class Amphibia and the order Anura. Poison dart frogs belong to the family Dendrobatidae within the order Anura.
Facts About Poison Dart Frogs
The name "poison dart frogs" refers to a historical use of the animals. Hunters coated darts with a frog's toxic skin secretion and then used the darts in a blowgun to kill prey. The practice is still performed in some places, though with only a few of the species in the poison dart frog group.
The small size of the frogs may surprise some people. The animals are beautiful and potentially deadly, but most species are no longer than two inches when they are adults. The vivid colors of the animals in the group is an example of aposematic coloration. The colors advertise the toxicity of the amphibians to potential predators.
A dart frog's skin secretes a mixture of poisonous alkaloids. It gets the alkaloids from its diet. The identity of the prey that supplies the chemicals and the processes that occur in the amphibian's body to make the skin toxic are not completely understood. It's thought that the chemicals come from toxic ants, beetles, or millipedes that a frog eats.
When the frogs are fed a different diet in captivity, their toxic nature disappears. Anyone who wants to keep a poison dart frog in captivity should investigate a suitable diet and (if the animal was obtained from the wild) the time needed for the skin to become safe. A mistake could be deadly.
Blue Poison Dart Frog
The blue poison dart frog's current scientific name is Dendrobates tinctorius var. azureus. It was once classified in its own species as Dendrobates azureus but is now classified as a variety of D. tinctorius.
The frog lives in southern Suriname in patches of rain forest that are surrounded by savanna. Suriname is a small country located on the north coast of South America. The amphibian is also found in a very small area in Brazil.
The animal is about two inches long. Its body is bright blue and is decorated with dark blue or black spots, which are largest on its back. It has four toes on each foot. Each toe has a wider tip. As in other poison dart frogs, its eyes are dark.
The frog is diurnal (active during the day), so its colors can by seen by potential predators and by humans. The animal uses vision to find its insect prey. Once it discovers a suitable meal, its tongue shoots out and grabs the prey. In the video below, the amphibians can be seen tapping a toe on a hind foot as they feed on living food. The behavior has also been observed in other frog species. One theory to explain the behaviour is that the tapping creates vibrations that trigger the prey to move and make them easier to find.
A Threatened Variety
The Dendrobates tinctorius species as a whole is not in any trouble. Researchers are concerned about the status of the azureus variety of the species, however. It has a very limited distribution, and in some places its habitat is threatened by deforestation. It's also caught for the pet trade. People who want to keep the frogs in their home should obtain their animals from a breeder to help protect the wild population.
Strawberry Poison Dart Frog
The strawberry poison dart frog currently has the scientific name Oophaga pumilio. It was formerly known as Dendrobates pumilio. The animal may reach an inch in length but is often shorter. It's often bright red speckled with black. The legs and/or feet are partially blue.
Some members of the species are orange, blue, or green instead of red. The different appearances are known as color morphs. They may make identification difficult for a casual observer. Color morphs are forms of an animal that have different colors or patterns on their surface but in other respects are the same as the rest of their species or variety.
Oophaga pumilio lives in Central America near the coast. It's often found in forests but can also be seen in plantations and even in gardens. It feeds on insects, especially ants.
Reproduction in the Family Dendrobatidae
The method of reproduction in the strawberry poison dart frog (and in other members of the family Dendrobatidae) has some interesting aspects. As in other frogs, the males call to protect their reproductive territory and to attract females. Fertilization is external. The female lays her eggs and the male deposits sperm on top of them. Once the female has laid her eggs, the male urinates on them to keep them moist.
After the eggs have hatched, the female carries the tadpoles to the water-filled axils of leaves, especially those of bromeliads. The tadpoles are attached to their mother's body by mucus during their journey. One tadpole is deposited in each leaf axil. The female lays unfertilized eggs in the pool for the tadpole to eat.
A single "golden poison frog" harbours enough poison to kill 10 grown men.— BBC Earth
A Small and Very Toxic Amphibian
The scientific name of the golden poison frog is Phyllobates terribilis. It's an attractive little animal that can indeed be terrible. The identity of the most poisonous frog in the world is debatable, but this one is often given the title. Like the previous two frogs, it belongs to the family Dendrobatidae. One of its alternate names is the golden dart frog. It's commonly said that a single frog bears enough toxin to kill ten people. At the moment, there is no antidote for the poison.
The animal is often bright yellow, golden, or orange, but a pale green color morph exists. The species lives in the rainforest on the coast of Colombia. It spends its time on the forest floor and rarely climbs trees. It eats insects such as beetles, ants, termites, crickets, caterpillars, and flies. The frog is thought to live for six to ten years.
Batrachotoxin in Phyllobates
Frogs in the genus Phyllobates (such as the yellow poison frog) release a secretion containing batrachotoxin. The secretion is released by the top of the head and the back of the animal when it feels threatened.
Batrachotoxin affects the sodium channels in the cell membranes of nerve and muscle cells. The chemical prevents the channels from closing. As a result, a huge quantity of sodium ions enters the cells, interfering with their function. Our lives and the lives of other animals depend on nerves and on muscles such as those in the heart working properly. The toxin prevents them from doing this. Affected animals quickly die from heart failure.
The toxin has also been found in the skin and feathers of some birds and in beetles belonging to the family Melyridae. Scientists are studying the chemical not only to improve treatment for affected people but also to discover whether the chemical or its derivatives could have any benefit for us. Some toxins derivatives do have benefits when used in minute doses.
Scientists were once puzzled by the fact that the toxin doesn't affect the frog's own nerve and muscle cells. Researchers have discovered that the animals' sodium channels have a minor change in their structure that protects them from the toxin's effects.
The vast majority of us should never handle a wild poison dart frog, even if we're wearing protective gloves. The people in the video below are experts and know what they're doing. It's important that the wild animals survive not only for their own sake but also because chemicals in their secretion might be useful for us.
An Endangered Animal
Unfortunately, the golden poison frog is an endangered animal. The amphibian may be locally common, but its range is so small that it has been classified as an endangered species by the IUCN (International Union for Conservation of Nature). The species is said to be in trouble due to the clearing of land to grow illegal crops, pollution created when the crops are spayed, logging, and mining. The species is used in the pet trade, but it's thought that few wild animals are caught for this purpose.
Malagasy Rainbow Frog
The Malagasy rainbow frog (Scaphiophryne gottlebei) is endemic to Madagascar. It's found in the Isalo Massif region of southern Madagascar. The Isalo Massif is an ancient sandstone plateau. The area contains canyons as well as a plateau. The frog exists in different color morphs. It's also known as the painted burrowing frog and as Gottlebe's narrow-mouthed frog. The color and pattern on the body vary. Females may reach 1.6 inches in length. Males are a little smaller.
The animal is classified as fossorial. A fossorial species is a good digger and spends much of its time underground. The rainbow frog is sometimes seen above ground, however. In addition to being fossorial, it's scansorial (a climber). It climbs the steep canyons in its habitat when it needs to.
The canyons become flooded during the rainy season. The frog escapes the flooding of its burrows by hiding in holes that it discovers as it climbs the canyon walls. One benefit of the flooding is that when the water withdraws, small pools are left behind. The amphibian uses these pools for mating, egg production, and tadpole development. The tadpoles feed on detritus in the pools and complete their development rapidly.
Another Endangered Animal
The man who took the photos of the rainbow frog that I've included in this article studies the animal. In the video above, he shows the frog and describes his work by means of subtitles. He says that several hundred animals are exported every year for the pet trade. The researchers have attached small radio transmitters to the wild frogs in order to study their movement. The research could be very important. The species is classified as endangered by the IUCN.
There is continuing decline in the extent and quality of its habitat around Isalo, and collection for the pet trade is suspected to be unsustainable.— IUCN Red List (with respect to the Malagasy rainbow frog population)
Tomato frogs are native to Madagascar and belong to the genus Dyscophus. Three species exist. All of them are referred to as tomato frogs, but Dyscophus antongilii is the species with tomato-like colors. Females are red and males are orange. The other species are yellow brown or orange brown. The animals range from 2.5 inches to 3.5 inches in length. The frog has a dorsolateral fold on each side of its body. "Dorsolateral" means positioned between the back and the side. One of the folds can be seen in the animal below. In some animals, a dark line is visible beneath each fold.
The frog spends much of its time underground. It lives in a variety of habitats. The IUCN describes it as a "very adaptable" animal. It's found in rainforest, scrub, and even urban areas. A notable population occurs in the town of Maroantsetra, where the animal makes its home in people's gardens. It feeds on insects and worms.
The frog breeds in pools of water that it discovers. In Maroantsetra, these may be ponds or ditches. The eggs are black in color. Tadpoles emerge from the eggs after only thirty-six hours.
A Defensive Behavior
When D. antongilii feels threatened by a potential predator, it puffs up its body. If this tactic doesn't dissuade the predator from attacking, the amphibian's skin releases a thick and sticky secretion. The secretion blocks the predator's mouth and eyes and is toxic. Although in general the material is not believed to be harmful for humans, it has the potential to cause an allergic reaction in some people. This is important to keep in mind because the tomato frog is kept as a pet.
Glass frogs belong to the family Centrolenidae. Their colors and patterns may not be as dramatic as those of some frogs, but they have an intriguing feature that the other amphibians lack. The skin on the undersurface of some species in the family is translucent, enabling the internal organs and structures to be seen. The chest, belly, and underside of the legs may all be translucent. Sometime the beating heart and blood vessels of an animal are visible. The emerald glass frog is one species with "see-through" skin.
The translucent skin is a fascinating feature, but scientists don't have a definite explanation for its existence. It's believed to help camouflage the animals in certain situations, however. Though the emerald glass frog is a colorful animal when seen on the lightbox in the photo below, in its natural habitat it may be disguised.
The Emerald Glass Frog
The emerald glass frog (Espadarana prosoblepon) is emerald green in color, as its name suggests. The skin is flecked with black. The digits are paler than the body. They are sometimes a lovely yellow color, as in the animal above. The frog's eyes are large and bulge outwards. Unlike those of other types of frogs, those of glass frogs face forward. They are clearly visible in Espadarana prosoblepon because the iris is speckled yellow instead of being black. The animal is a little over an inch long. Like the other members of its group, it's mostly nocturnal.
According to the University of California's AmphibiaWeb site, the animal is found in Colombia, Costa Rica, Ecuador, Honduras, Nicaragua, and Panama (or at least it was when the database was last updated). It lives in forests. Most of its diet consists of insects.
When the mating season arrives, the male establishes a territory in a tree and calls to attract a female. The female usually lays her eggs on a leaf or a branch that is located above water. The male then fertilizes the eggs. When the eggs hatch, the tadpoles drop into the water below to complete their development.
AmphibiaWeb provides some interesting information about the interior of the animal. The animal's intestine and its bones can seen through its translucent ventral surface, though the upper part of the body is hidden by a membrane. The bones are said to have a green tinge due to the presence of a pigment called biliverdin. This helps them to blend in with the leaves when the animal is seen from below.
Studying nature can be a fascinating pursuit. Many other interesting frogs exist besides the ones discussed in this article. Brightly colored frogs are especially attractive, but all of them can be useful to study. Nature is often educational as well as engrossing. By learning about aspects of amphibian lives and studying the chemicals that they make, we may discover some useful facts related to human biology and health problems. That could be a great outcome.
- Information about poison dart frogs from the BBC Earth
- Blue poison dart frog facts (as well as facts about other species) from Aquarium of the Pacific in Long Beach, California
- Information about Oophaga pumilio (and facts about other species) from AmphibiaWeb, University of California, Berkeley
- Golden poison frog from National Geographic
- Status of Phyllobates terribilis from the IUCN Red List
- Information about batrachotoxin from ScienceDirect
- The chemistry of poisonous frogs from Compound Interest
- Gottlebe's narrow mouthed frog from the Encyclopedia of Life
- Malagasy rainbow frog from Edge of Existence
- Status of the Malagasy rainbow frog from the IUCN
- Tomato frog from Smithsonian's National Zoo and Conservation Biology Institute
- A description of Espadarana prosoblepon from AmphibiaWeb, University of California, Berkeley
© 2020 Linda Crampton