Black frogs and toads are some of the most fascinating amphibians out there. Their dark coloration allows them to camouflage seamlessly into their environments. In this article, we’ll explore some of the most interesting black frog and toad species found across the globe.
While green and brown are the most common frog colors, there are a surprising number of black frog and toad species. Their black pigmentation likely evolved as a form of camouflage, allowing them to blend into dark environments.
Black coloration provides an array of benefits
- Camouflage from predators and prey
- Increased heat absorption from sunlight
- Signaling to potential mates
Black frogs and toads inhabit all continents except Antarctica. They dwell in diverse ecosystems including rainforests, mountains, deserts, and swamps. Let’s take a look at some of the most remarkable black amphibians around the world.
Notable Black Frog and Toad Species
Black Rain Frog
Native to South Africa, the black rain frog lives up to 15 years. It earned its name from its dark coloration and tendency to emerge after rainfall. These portly frogs grow up to 2 inches long and use their burrowing skills to escape predators.
Roraima Bush Toad
Found solely on the tepui mountaintops of Venezuela, the Roraima bush toad is critically endangered. At less than an inch long, this species boasts an entirely black appearance with warty skin. It inhabits the open, rocky terrain of these isolated tabletop mountains.
Tasmanian Froglet
The Tasmanian froglet is one of the rarest black frogs, existing only in Tasmania. Its color ranges from solid black to dark brown with a red stripe along the spine. These small frogs frequent shallow waters and temporary pools by rivers.
Mexican Burrowing Toad
This large toad inhabits Central America and is identifiable by its velvety black skin with a vibrant red dorsal stripe. It’s equipped with robust front legs for digging burrows up to 3 feet deep to escape hot, dry conditions. Females can grow up to 5.5 inches long.
Black Toad
The aptly named black toad lives solely in a few springs within California’s Deep Springs Valley. It flaunts black spots scattered over a pale brown body and doesn’t vocalize beyond soft chirps. Though abundant in its tiny range, habitat changes pose conservation concerns.
Yellow-Banded Poison Frog
With bright yellow stripes contrasting against jet black skin, the yellow-banded poison frog warns predators of its toxicity. It secretes potent alkaloid poisons from its skin to deter predators, with levels high enough to potentially kill a human. This species inhabits rainforests in Central and South America.
Unique Features of Black Frogs and Toads
Beyond their dark pigment, black frogs and toads boast many distinctive traits and adaptations:
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Camouflage – Their ebony hue provides concealment against dark, wet environments. Some species even have spotted patterns to blend into dappled light.
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Toxicity – Poison frogs like the yellow-banded secrete alkaloid toxins as a defense mechanism, accumulating these compounds from their diet. Their vivid coloration advertises their toxicity.
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Burrowing – Certain toads and frogs burrow into the ground to escape heat, dryness, and predators. Their muscular legs provide digging power.
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Arboreality – Tropical tree frogs have strong toes and fingers to grip branches and traverse their arboreal habitats. Their dark color camouflages them in the canopy.
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Parental care – Some amphibious fathers guard their eggs after the female lays them. They may transport tadpoles on their back to water sources.
From tiny poison dart frogs to chunky rain toads, black amphibians have evolved a plethora of superb adaptations for life on land and in water. Their dark pigment allows them to vanish against wet rocks and soil. Hopefully this overview has shed some light on these elusive ebony jewels of the amphibian world. Let us know if it has inspired you to learn more about these cryptic hoppers!
Anaxyrus exsulBlack Toad
Black toads (Anaxyrus exsul) are limited to the eastern border of California. The entire population is patchily distributed within an area of 15 ha. They are found as far north as Antelope Spring and as far south as Deep Springs Lake. There is also a disjunct population near Salt Lake City, Utah. (Hammerson, 2004; Lannoo, 2005)
- Biogeographic Regions
- nearctic
- native
Black toads are limited to less than a dozen inland freshwater springs within a single desert basin. Their habitats consist of marshy wetlands formed by rainwater in the desert biome. They are more commonly found in areas with shallow water and an abundance of vegetation. When breeding, they choose areas such as marshes and bogs. These water sources have an elevation of 1,450 to 1,700 m. When black toads are still young, they are found in shallower waters where they can mature completely. Vegetation surrounding water sources consist of beard grass (Polypogon), common rush (Juncus), buttercups (Ranunculus), sedges (Carex), duckweeds (Lemna), and more plants. In Anaxyrus, black toads are most tied to aquatic habitats. These toads have never been found more than 12 meters from the water. (Hammerson, 2004; Lannoo, 2005; Livezey, 1962; Schuierer, 1962)
- Habitat Regions
- temperate
- terrestrial
- freshwater
- Terrestrial Biomes
- desert or dune
- Aquatic Biomes
- rivers and streams
- Wetlands
- marsh
- swamp
- bog
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- Range elevation
- 1,450 to 1,700 m
- to ft
Black toads are primarily black with distinguishable features including light stripes and dots throughout their bodies. Males and females have differing physical features. Males have lighter colored throats and smaller body masses, while females are slightly larger with more spots. The average snout-vent length (SVL) of a male A. exsul is 50 mm, while the average SVL for a female is 52 mm. The average snout-vent length as fully matured adults ranges from 44 mm to 76 mm.
When the eggs are laid, it takes 4 to 5 days from them to hatch. They remain as tadpoles for 3 to 5 weeks. Tadpoles can reach up to 35 mm long. Throughout their physical development, black toads turn from an olive color to an ebony or brownish black. (Hammerson, 2004; Lannoo, 2005; Schuierer, 1962)
- Other Physical Features
- ectothermic
- bilateral symmetry
- poisonous
- Sexual Dimorphism
- female larger
- sexes colored or patterned differently
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- Range length
- 44 to 76 mm
- 1.73 to 2.99 in
Once black toad eggs are fertilized, they hatch in the next four to five days. They remain in the larval stage for three to five weeks until they metamorphose into adults. These toads have indeterminate growth and take less than a year to fully mature. Tadpoles can grow to be 35 mm. The average length of newly metamorphized black toads ranges from 14 to 19 mm, and increases to 22 to 33 mm SVL by the end of their first year. Adult female black toads have an average SVL of 52 mm, while adult males have an average SVL of 50 mm. Sex is evident only after full development. (Lannoo, 2005; Schuierer, 1962)
- Development – Life Cycle
- metamorphosis
- indeterminate growth
Breeding occurs in water sources such as marshy areas and ponds. Black toads are polygynandrous. Due to their lack of vocal sacs, male black toads have a weaker, high pitch release call but do not have a specific advertisement call. Females can also produce release calls. During breeding, black toads join in amplexus where a male attaches to a female’s back. Males externally fertilize the female’s eggs. Once complete, the eggs are left hidden in vegetation in the water. (Lannoo, 2005; Livezey, 1960; Schuierer, 1962)
- Mating System
- polygynandrous (promiscuous)
Black toad mating season takes place in the spring from March to April. Females are oviparous and iteroparous, meaning that they lay multiple clutches of eggs across multiple seasons. They can ovulate in November, but lay their eggs in the spring. Once external fertilization occurs, eggs are linked together and commonly dropped in close proximity to each other in shallow vegetated areas. Approximately 16,000 eggs are laid at one time, and they take three to five days to hatch. Birth mass has not been reported.
Adults leave their eggs after breeding, young are fully independent upon hatching. There is no reported age at sexual maturity. Once fully developed, the average female snout-vent length is 52 mm while the average male SVL is 50 mm. (Lannoo, 2005; Livezey, 1960; McDiarmid and Altig, 2015; Schuierer, 1962)
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- Breeding interval
- Black toads breed once yearly
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- Breeding season
- March-April
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- Average number of offspring
- 16,000
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- Range time to hatching
- 3 to 5 days
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- Average time to independence
- 0 minutes
Black toads do not have any type of parental investment. Once mating occurs, black toad parents leave and do not return to the mating site. Therefore, there is no parental investment beyond the act of mating. (Lannoo, 2005)
- Parental Investment
- no parental involvement
There are no known records of the lifespan of black toads. Another species within the genus, western toads (Anaxyrus boreas), have a lifespan of 6 years in the wild. It is suspected that black toads have a similar lifespan. (Lannoo, 2005)
Black toads are an active species. Adults are diurnal but become nocturnal during hotter months. They are slow and inactive at temperatures about 25˚C and generally more active in temperatures ranging between 17 to 22˚C. They are active from May to September and are a non-migratory species.
Black toads are normally found in clusters resting. Males were commonly found closer to breeding sites than females. During hibernation, they group together in small holes made by rodents. These burrows are commonly found above water level, between 25 and 50 cm away from a water source. The exact months of hibernation have not been reported, but black toads are active from May to September. They are generally aquatic and swim similarly to frogs. When on land, black toads commonly walk slowly or hop in short bursts. (Hammerson, 2004; Lannoo, 2005; Livezey, 1962; Schuierer, 1962)
- Key Behaviors
- saltatorial
- diurnal
- nocturnal
- motile
- sedentary
- hibernation
- social
The home range for black toads is not reported, but these aquatic toads are never more than 12 m away from water. They are not reported to defend a territory. (Gordon, 2017; Lannoo, 2005; Schuierer, 1962)
Black toads are mainly aquatic. They inhabit marshes and other water sources near the surface. Black toads have color vision. they are capable of communicating audibly with each other, but male toads do not have vocal sacs. Male intraspecific communication includes low-pitch chirps. Females can emit release calls when they are disturbed.
Before mating occurs, male black toads are typically motionless and do not approach the females first. Tactile communication is necessary, as toads mate while in amplexus. Males fertilize the eggs that females externally release into the water.
Due to summer heat, toads will be more active at night or early in the morning. When toads hibernate, they crowd together in rodent holes near water sources. Another toad species within the family Bufonidae can emit alarm pheromones as tadpoles. It is possible that black toads may also use pheromones as tadpoles. (Hagman, 2019; Lannoo, 2005; Schuierer, 1962)
- Communication Channels
- visual
- tactile
- acoustic
- chemical
- Perception Channels
- visual
- tactile
- acoustic
- chemical
The diet of black toads consists mainly of insects. These insectivores eat smaller insects such as ants and beetles. They hunt mainly in the early mornings and late evenings to avoid mid-day heat. The main difference in eating habits between adults and developing young is the size of their prey. Tadpoles feed on organic material and minerals suspended in the water. Younger toads eat ants, wasps, and mites, while fully mature toads eat larger insects such as beetles and Lepidoptera larvae. Diptera, Coleoptera, and Hymenoptera species were present most frequently in adult and juvenile black toad stomachs. Mites and mollusks were found most frequently in juveniles. (Lannoo, 2005; Livezey, 1962; Schuierer, 1962)
- Primary Diet
- carnivore
- insectivore
- Animal Foods
- insects
- terrestrial non-insect arthropods
- mollusks
- Other Foods
- microbes
Avian and mammalian species have been found to eat black toads. Common ravens (Corvus corax), Virginia opossums (Didelphis virginiana), and common carp (Cyprinus carpio) have been reported hunting black toads from their breeding sites. The toads can emit a toxic secretion from their parotid glands for defense. (Hammerson, 2004; Lannoo, 2005; Olson, 1989)
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- Known Predators
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- Virginia opossums (Didelphis virginiana)
- common ravens (Corvus corax)
- common carp (Cyprinus carpio)
Black toads’ predators include larger mammals, birds, and fish. Black toads prey on insects such as ants (family Formicidae) and beetles (order Coleoptera). Unknown intestinal roundworms (order Nematoda) have been found in black toads, as well as leeches (subclass Hirudinea) found visibly on toads. (Lannoo, 2005; Olson, 1989; Schuierer, 1962)
- Leeches (Hirundinea)
- Intestinal roundworms (Nematoda)
Economic Importance for Humans: Positive
There are no positive economic impacts of black toads on humans.
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FAQ
How rare is a black toad?
Although two population studies indicate a stable population, the black toad has among the smallest range of any North American anuran which puts the species in a potentially precarious position, especially considering that its requisite aquatic habitat is surrounded by desert.
What are black frogs called?
Black frog may refer to: Black microhylid frog (Melanobatrachus indicus) a frog in the family Microhylidae endemic to the Western Ghats, India. Black rain frog (Breviceps fuscus), a frog in the family Brevicipitidae endemic to South Africa.
Why are black toads endangered?
Habitat alterations and individuals collecting this species from its habitat can lead to a population decline. Road systems, human activity, natural alterations due to weather, and predation all threaten black toads.
Are black rain frogs good pets?
Not good pets. They don’t breed in captivity and are all wild caught. Unless they are being captive bred no animal makes a good pet. They are an important part of their ecosystem and that’s just not sustainable.