Poisonous Secrets of the Amphibian World
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It’s thought that there are around 175 species of toxic amphibians in the world. From dart frogs to salamanders, these remarkable amphibians have evolved potent defense mechanisms that serve as formidable deterrents against predators.
Join us as we explore the diverse range of toxic amphibian species, unraveling the mysteries behind their unique adaptations and uncovering the secrets of their extraordinary defensive capabilities.
What are Amphibians?
Amphibians are animals that are able to live on both land and in the water once they reach their adult stage. However, before this, they undergo the process of metamorphosis changing from their larval form into fully-fledged adults that we recognize like frogs, toads, and newts.
When they are young, amphibians are tadpoles. They hatch from jelly-like eggs known as spawn and, during this stage, remain in the water.
These creatures are unlike reptiles since they do not have scaled skin. Instead, it is much smoother. While they breed in the water, like fish, they differ in that they have lungs that allow them to breathe oxygen in the air.
Amphibians are cold-blooded vertebrates; meaning they have a backbone, and there are three main types. These are frogs and toads, newts and salamanders, and caecilians which are wormlike creatures.
Some amphibians are poisonous, although this isn’t a trait we see in all amphibious species. For the purpose of this article, I’ll be focusing on those that are toxic.
Do all Amphibians Carry Poison?
There are more than 8000 amphibian species on earth, but only around 175 of these are known to be poisonous. Among these toxic species are also two venomous species; the Greenings Frog and Bruno’s casque-headed frog. Poisonous frog species include the group known as poison dart frogs as well as species such as the natterjack and cane toads.
It’s important to understand the difference between poison and venom. Poisonous animals deliver their toxins usually via their skin. It enters into the victim’s body through inhalation, ingestion, or is absorbed into the skin where it enters the bloodstream.
On the other hand, animals that are venomous must inflict a wound to their victim in order for the toxins to enter. In many cases, this is done via a bite, scratch, or sting.
Toxic Amphibian Species
The world is home to hundreds of toxic amphibian species, each with its own unique traits. In order to get to know these animals a little bit better, I’ve put together some information on the most fascinating poisonous amphibians.
1. Golden Poison Dart Frog (Phyllobates terribilis)
The golden poison dart frog holds the title of the most poisonous amphibian. It’s so toxic that one might say that it was almost at the top of the food chain. That’s if it weren’t for the fire-bellied snake which is the only animal that predates this poisonous little froggy.
Bright yellow in color and residing in the forests of Columbia, this small creature has sadly become endangered owing to habitat loss. There are some examples of this frog that come in other colors, including orange and mint green. While they might look cute, a single frog has enough toxins to kill up to 10 people, even just by touching them.
In order to poison anything that tries to eat it, the golden dart frog secretes a toxin through its skin containing a chemical known as batrachotoxin. This poisonous substance affects the sodium channels within the nerves and is only known to be secreted by three amphibious species.
2. Greening’s Frog (Corythomantis greeningi)
Most amphibians deliver their toxins as a poison, but the Greening’s Frog is one of two exceptions since it is considered venomous. But while most venomous animals will bite their victims, the Greening’s Frog has a rather unique method of delivery; it uses its head!
These frogs, which are found in the northeastern part of Brazil, have bony spines on their heads which they use to penetrate their victims and inject their venom. They do this as a method of self-defense, including when humans are a threat. What’s interesting is they’re they’re even able to use their cranial weapons when they are restrained thanks to an ability to twist their bodies under pressure.
Fortunately, during studies when a researcher was envenomated, the consequences were not fatal, and the researcher experienced pain for around five hours.
3. Fire Salamander (Salamandra salamandra)
The fire salamander is a stunning creature with bright yellow markings over a shiny black skin. However, an appearance like this is usually designed to let would-be predators know to stay well away and that’s certainly the case with this critter.
Fire salamanders are commonly found in forested areas around central Europe. They’re equipped with a toxin called samadarin which can cause convulsions and hypertension. Not only is the toxin contained within the skin but the animal has glands behind the eyes that allow it to spray poison at an attacker.
However, these creatures are not a massive threat to humans unless the toxin is ingested. In fact, they’re common in the European pet trade and, as long as you wash your hands after handling them, fire salamanders won’t cause any irritation.
4. Cane Toad (Rhinella marina)
The cane toad is a common species that is found in tropical forests around central America, southern parts of the United States, and northern areas of South America in countries such as Peru.
The cane toad has glands all over its back, which allow it to secrete a toxin known as bufotoxin, which affects the cardiovascular system. As with other species of poisonous amphibians, they use this as a defense mechanism.
Interestingly, the cane toad is toxic even when it is a tadpole which isn’t something we see in all poisonous amphibians. While the toxins aren’t usually fatal to humans, they are known to kill dogs and other animals, so it’s important to keep pets away from them.
5. Harlequin Poison Frog (Oophaga histrionica)
The harlequin poison frog is a species native to Ecuador and Columbia and is found in tropical forests. Unfortunately, this species has been listed as endangered as a result of habitat loss. While efforts are being made to conserve them, it’s difficult as breeding them in captivity has proven to be especially challenging.
Harlequin poison frogs produce histrionico toxins which are a type of cardiotoxin with moderate to high toxicity. While these toxins aren’t usually known to kill humans, they are capable of having serious effects on the neurological system.
6. Colorado River Toad (Incilius alvarius)
You might know this toad as the Sonoran desert toad as that used to be its name. As far as toads go, I think this is a cute critter. But beware, it might look innocent, but it packs a punch with its toxins. These psychoactive toxins are so potent that they’d easily kill a fully-grown dog.
Incredibly, humans have been known to lick toads or even smoke their secretions for the psychedelic effects. However, authorities have issued warnings against this where the Colorado river toad is concerned, as ingesting the toxins could make you very sick.
Found in North America throughout the Arizona and Sonoran deserts, this is a very common species that is not currently considered at risk.
7. Green-and-Black Poison Dart Frog (Dendrobates auratus)
The green-and-black poison dart frog is perhaps one of the most famous poisonous amphibians and can be found on the rainforest floors in Central and South America. With a bright green body and deep black markings, they’re certainly an attractive looking species. But as with all toxic froggies, looks can be deceiving.
Green-and-black poison dart frogs secrete a toxin through their skin when it feels threatened. It isn’t as toxic as some other species, but when exposed to enough of the poison, it could be enough to kill a human.
What’s interesting is that these frogs are often kept in captivity and, when they are, they’ve been seen to lose much of their toxicity. It’s thought that the reason for this is a lack of a wild diet which is believed to help the frog produce its toxins.
8. Strawberry Poison Frog (Oophaga pumilio)
With a deep red body and brightly colored blue legs, the strawberry poison frog is certainly one of the most beautiful poisonous amphibians. These small creatures are found mainly in South America and prefer a rainforest habitat, although they’re sometimes spotted in banana plantations.
These frogs produce a pumiliotoxin from their diet of ants and mites which is then secreted from the skin and affects the cardiovascular system of anything that ingests it.
The strawberry poison frog not only uses its toxins to defend itself, but it’s the ultimate caring parent as it gives toxins to its young when they’re in the tadpole phase to prevent them from being gobbled up by predators.
9. Bruno’s Casque-Headed Frog (Aparasphenodon brunoi)
I have already talked about one species of venomous frog, and the only other one is this one; Bruno’s casque-headed frog. In a similar way to the Greening’s frog, this species has those bony structures on the head that it forces into the skin of its enemy, delivering the venom.
These frogs are found only in the southeastern parts of Brazil and enjoy a forest habitat where they can often be found hiding out in trees and old logs.
The venom of Bruno’s casque-headed frog is extremely toxic to humans. Just a single gram of the frog’s toxin is capable of killing 80 humans.
10. Yellow-Banded Poison Dart Frog (Dendrobates leucomelas)
Sometimes called the bumblebee poison frog because of its black and yellow appearance, the yellow-banded poison dart frog is a mid-sized species that only grows to around 1.2-2 inches (3-5 cm). This may seem small but keep in mind that many poisonous dart frogs are no bigger than 0.8 inches (2 cm).
Yellow-banded poison dart frogs are found in humid parts of northern South America and are able to secrete a toxin from their skin, including alkaloid toxins and neurotoxins. When ingested, these toxins can cause nerve damage and even lead to heart failure.
While the toxins of the yellow-banded poison dart frog are capable of killing humans, this is unlikely. However, other symptoms can occur, so it’s best to leave these critters to their business and admire them from afar.
11. Natterjack Toad (Epidalea calamita)
The natterjack toad is a species native to Europe and can grow up to 2.8 inches (7 cm) in length. These toads are known for their loud mating call and unusual gait, which differs from that of other toad species thanks to their stumpy legs.
Natterjack toads, like most other poisonous amphibians, have the ability to secrete toxins from their skin. While this is done as a protective measure against predators, it has been noted that grass snakes and certain species of birds, such as the rook and magpie, are able to eat natterjack toads without suffering any ill effects.
Where humans are concerned, the toxins are not fatal. However, they can cause irritation and, in some people, an allergic reaction may follow.
12. Panamanian Golden Frog (Atelopus zeteki)
As the name may suggest, the Panamanian golden frog is native to Panama where it can be found living around mountain streams. These frogs are actually a species of true toad and owing to their stunning appearance, they are one of the national symbols of their native country.
Panamanian golden frogs possess a large number of toxins, including guanidinium, bufadienolides, tetrodotoxins, and alkaloids. These affect the nerve cells and, in studies, have been shown to kill mice as a result of respiratory and circulatory failure.
13. Apennine Yellow-Bellied Toad (Bombina pachypus)
The apennine yellow-bellied toad is an endangered species of poisonous amphibian that is mainly active during the day. That’s not a common trait in toads but it’s thought that, in order to best show off its bright warning colors, being around at night wouldn’t make sense.
But those bright colors are on the underside of the toad, hence its name. So, when it is threatened it will display its belly as a warning. However, if this does not work, the toad will secrete toxins from its skin.
While these toxins are effective in defending the toad, it’s interesting that they also have antibacterial and antimicrobial properties so could be useful to humans.
14. Splash-Backed Poison Frog (Adelphobates galactonotus)
The splash-backed poison frog gets its name from the brightly colored marking on its back that makes it look as though it’s been splashed with paint. It’s found exclusively in Brazil around the Amazon Basin, and while it is widespread, it does face some threat from habitat loss.
Splash-backed poison frogs use their markings to tell predators to stay aware and warn them that they’re poisonous. While the frogs’ markings can come in several different colors, it’s not thought that this has any effect on the type of toxins they produce.
Among some of the rarest frogs owing to their compact distribution, the splash-backed poison frog is thought to be one of the most highly toxic species.
15. Rough-Skinned Newt (Taricha granulosa)
The rough-skinned newt is a commonly found species in North America, particularly along the Pacific coast. While they are not considered to be endangered, there is a risk that they may start to struggle if habitat destruction continues.
Rough-skinned newts produce a toxin from their skin, just like many other poisonous amphibians. However, what’s special about these animals is that, with this toxin, comes a potent odor that serves as another warning to predators.
For humans, the toxin is not usually life-threatening, although there was one recorded incident of human death in the late 70s after the victim touched a rough-skinned newt. The toxin is effective against most predators, but there has been some discussion that animals like the common garter snake may be resistant to the tetrodotoxin produced by these animals.
16. Phantasmal Poison Frog (Epipedobates tricolor)
Sometimes called the candy cane frog due to its red and white striped appearance, the phantasmal poison frog is not only known for being toxic but also for its bright chirruping early in the mornings.
But while its calls and appearance may be super cute, you’d better watch out, as these frogs are very toxic. That said, there has been research to suggest that the toxins they secrete through their skin could be used in the creation of non-opiate painkillers. What’s more, it’s been noted that the toxins have a very similar structure to that of nicotine.
These adorable little frogs are found around the Andes mountains in Ecuador and Bolivia. However, they are listed by the IUCN Red List as being vulnerable, largely due to its limited range.
17. Spotted Salamander (Ambystoma maculatum)
Similar in appearance to the fire salamander I discussed earlier in this guide, the spotted salamander has a black body with bright yellow markings. It is found in North America both in the United States and Canada.
These animals are usually found around ponds and in forested areas and grow to around 3.5 inches (9 cm) with a stout body. Around the neck and the back, the spotted salamander has poison glands that excrete toxins when it is threatened.
However, it’s unlikely that humans will come into contact with the spotted salamander since they spend most of their time underground. What’s more, they can live for around 30 years and even regenerate limbs when one is lost!
18. California Newt (Taricha torosa)
As many as five species of newt are found in California, and the California newt is, unsurprisingly, one of them.
One of the most interesting things about the California newt is that it’s able to protect itself even when in egg form. That’s because the gel that surrounds the eggs is also toxic, ensuring that predators don’t get the young before they’ve even had a chance to hatch.
As adults, these newts will primarily defend themselves by taking on an intimidating stance. But if this doesn’t work then they will secrete a neurotoxic poison from their skin which will paralyze or even kill their attacker.
19. Black-Legged Dart Frog (Phyllobates bicolor)
As its name suggests, the black legged dart frog can be identified by the black markings on its legs, while the rest of the body is a yellow to green color. These frogs are the second most toxic type of poison dart frog and can be found in Central and South America.
They possess a batrachotoxin which has the ability to kill a human. The frog secretes this from its skin and is able to produce the toxin thanks to components within its diet.
The toxins work by attacking the neurons which eventually leads to muscles shutting down. This results in the failure of essential bodily systems such as the cardio and respiratory systems.
20. Blue Poison Frog (Dendrobates tinctorius azureus)
Blue poison dart frogs are, as you would imagine, bright blue in color with speckled black markings. They are found in northern parts of Brazil and across Suriname, particularly around the Sipaliwini Savanna.
Owing to their limited distribution, these frogs were only recently discovered, with the first sighting in 1969.
Like many other types of poisonous amphibians, the blue poison frog secretes a toxin from its skin to attack predators. It’s pretty potent and has the power to kill but isn’t usually enough to be fatal to humans. This, along with the fact that their captive diet reduces their toxicity, means that blue poison frogs are popular in the pet trade.
The problem with this is that wild numbers are in decline and there is now concern over their survival. So much so that they’re considered to be one of the most at risk species.
21. Dyeing Poison Dart Frog (Dendrobates tinctorius)
Found only in the northeastern parts of Brazil and French Guinea, the dyeing poison dart frog is one of the least widespread species of poisonous amphibians. They’re found in humid regions and can often be seen hiding among the vines, where their bright yellow markings make them stand out.
It’s these markings that serve as an initial warning to predators but if they don’t take heed, the dyeing poison dart frog secretes its toxins. In this case, it’s a concoction of pumiliotoxin and allopumiliotoxins which are known to cause pain and stiffness when on the skin.
However, these toxins are not as potent as the batrachotoxins found in many species, so these frogs aren’t considered as much of a risk to humans.
22. Ringed Caecilian (Siphonops annulatus)
The final creature on my list is the ringed caecilian which is a venomous worm-like amphibian. It actually holds the world record for being the first-ever amphibian known to have venom glands in the jaw. This means that it can bite and deliver its toxins as opposed to simply secreting them.
These large wormy animals are found in South America and can grow up to 6.9 inches (17.5 cm) in length. For all intents and purposes, they look pretty defenseless so it comes as quite a shock that they can deliver a potent bite. However, their toxins aren’t only useful in biting but can also be secreted in the form of a mucus that helps the animal when burrowing.
What’s interesting is that scientists have discovered that the reigned caecilian’s venom glands are remarkably similar to those we see in reptiles. Although, it’s thought that these were independently developed early in their evolution.
Importance of Amphibian Toxins to Science
Most people live in fear of toxic animals and I’m under no illusion that we should be respectful of them. After all, some of them have the ability to kill us merely by touch. But it’s not all scary since scientists are finding ways to use amphibian toxics for human benefit.
Because of this, there has developed a significant focus on saving endangered poison frog species both for their own benefit and that of humans.
Frog toxins have long been used in folk medicine, but as humans become more resistant to drugs like antibiotics, pharmacists are having to get more creative. For example, the fire-bellied toad’s toxin is known to have wound healing abilities and is only around one year away from being trialed on humans.
Other potentially useful species include the various frogs that are susceptible to a fungal disease called Chytridiomycosis. Scientists are still working on the ins and outs of it but it would appear that some species are more resistant to the disease than others. In order to protect those that become fatalities, researchers are looking into what exactly makes some species less prone to succumbing to the effects of the disease.
Not only that but the toxin of the most poisonous frog in the world, the golden poison dart frog, could give scientists a look into how electrical impulses are conducted in nerves and muscles, allowing them to look at the function of pain and the heart.
There is even research taking place to develop painkillers using frog poison. However, as things stand, the only successful attempt at this has led to a medicine so toxic that it isn’t safe for human consumption.
Why Don’t Toxic Amphibians Poison Themselves?
If poisonous amphibians literally ooze toxins then it begs the question of why these toxins have no effect on the animal itself. It’s a curiosity but not one that can’t be answered.
It was once believed that animals like the golden poison dart frog had mutations within the sodium channels that prevented them from being attacked by their own toxins. However, there is little evidence to support this, and in studies, scientists have now seen that, while the frogs were resistant to the poison, this was not to do with any adaptation of the sodium channels.
But what exactly causes this resistance? Well, another study took amino acids from the muscles of poison dart frogs and transferred these into rats. When exposed to the toxins, the rats suffered no adverse effects. Therefore, this tells us that the amino acids found in the frog’s muscles offer protection from the poison.
Other research suggests that poison frogs are able to produce something of a sponge that soaks up the proteins in the toxins and holds onto them, instead of allowing them to be transported around the body.
