Poison dart frog
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 Red and Blue "Blue Jeans" poison dart frog, Dendrobates pumilio.
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 Distribution of Dendrobatidae (in black)
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Proposed Subfamily Colostethinae
Proposed Subfamily Hyloxalinae
Proposed Subfamily Dendrobatinae
Proposed obsolete (invalid) Dendrobatidae genera: |
The poison dart frog, poison arrow frog, dart frog or poison frog, is the common name given to the group of frogs belonging to the family Dendrobatidae. Poison dart frogs are native to two geographical regions: Central America and South America. The Green and Black Poison Dart Frog (Dendrobates auratus) has been introduced to a few Hawaiian islands.
Note: Poison frogs are widely called poison arrow frogs or poison dart frogs, reflecting the widespread notion that the frogs are used by indigenous South American tribes in the manufacture of poison that is spread on arrows or blow-gun darts. Since most of the species are not used for this purpose, many experts prefer that poison frog is used for the group's common name.
The skunk frogs and relatives have now been separated in a distinct family, Aromobatidae (Grant et al, 2006).
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[edit] Background
Poison dart frogs are a group of small, diurnal, and often brightly colored frogs native to Central and South America. These frogs received their common name from the numerous types of poisonous alkaloids found in the skin of many species. The most poisonous dart frog is the Golden Poison Dart Frog (Phyllobates terribilis).
Poison dart frogs are popularly characterized by their brightly colored skin and small size. The skin color can range from bright orange and black to blue or yellow. However, members of the most species-rich genus, Colostethus, are generally brown. Poison dart frogs range in size from 1 centimetre (0.2 in) to 6 centimetres (2.5 in) in length, depending on the age and species of the frog.
[edit] Toxicity
According to amphibian expert William Duellman, there are about 220 species of poison frogs. Most species are not toxic to animals and humans. More than 100 toxins have been identified in the skin secretions of poison dart frogs, especially Dendrobates and Phyllobates. Members of the genus Dendrobates (of which there are at least 44 known species) are also known as "poison dart" or "poison arrow" frogs. However, only frogs of the genus Phyllobates produce the extremely potent neurotoxin, batrachotoxin, and its derivatives. Even a very small amount of the batrachotoxin found in the skins of the Golden Poison Dart Frog and at least two other species of Phyllobates frogs - on the order of just 40 micrograms - can be fatal. For the Golden Poison Dart Frog, merely touching the frog's back with the tip of the tongue could be enough to transfer a lethal dose of poison (which is most readily absorbed via mucous membranes).
Certain tribes in South America, such as the Noanamá Chocó and Emberá Chocó indians of western Colombia, dip the tips of their blowgun darts in the poison found on the skin of three species of Phyllobates. In north Chocó, Phyllobates aurotaenia is used while to the south, in the departments of Risaralda and Choco, P. bicolor is used. In Cauca, even southern Cauca, P. terribilis is used for dart making. (Despite sometimes being called "poison arrow frogs" no examples are known of arrows, as opposed to darts, being poisoned with Phyllobates poison). No other species are used for this purpose. The poison is generally collected by roasting the frogs over a fire, but the toxins in P. terribilis are so strong that it is sufficient to dip the dart in the back of the frog without killing it.
The Matsés or Mayoruna tribe from the peruvian and brasilian Amazon inject the "sweat" or exudate of Phyllomedusa bicolor into their bodies in preparation for hunting. The Mayoruna Poison Frog ceremony is also practiced by the Matis and Marubo tribes and is thought to give one increased hunting ability. The use of the frog poison is only medicinal, and they do not, however, use the poison on darts or other hunting implements.
When a wild animal is shot with a poison-tipped dart, it will die within minutes from the neurotoxin, making additional shots unnecessary to kill it. Poison darts made from either fresh or fermented batrachotoxin are enough to drop monkeys and birds in their tracks since nerve paralysis is almost instantaneous.
There is considerable evidence that toxicity in these frogs is derived from their diet: primarily ants, mites, and beetles. These toxins are passed from the arthropod to the frog, then sequestered in glands on the amphibian's skin. Frogs brought from the wild into captivity and fed a regular captive diet, usually fruit flies or pin-head (hatchling) crickets, eventually lose their toxicity.
[edit] Reproduction and parental care
The majority of members of this family of frogs that have been studied are characterized by unusual reproductive strategies for amphibians. In the genus Colostethus eggs are laid on the forest floor by the female following often elaborate courtship behaviors by the male. One parent (generally the male) guards the eggs until they hatch. The newly hatched tadpoles wriggle onto the back of either the male or female parent, who transports them to water. In some members of the genus Dendrobates, tadpoles are carried to small pools of water isolated in treeholes or other phytotelmata. In a few species, females return repeatedly to these treeholes to feed the tadpoles unfertilized nutritive "nurse" eggs, which the tadpoles rely on as a major (or only) source of food. Parental behaviors of this highly complex sort are quite rare among amphibians.
[edit] Poison frogs in captivity
In captivity, poison dart frogs typically have a lifespan of 5 to 12+ years, but little data exists for wild frogs. Most species reach maturity around 1.5 to 2.5 years of age. The easiest way to determine the sex of a particular species of poison dart frog is by observation in the wild. Mature male frogs will usually make a mating call after eating or after a heavy misting of water. The sound is similar to that of a series of high-pitched "clicks". In juvenile frogs the sex can sometimes be determined by the profile of the amphibian. The backs of males usually slope down with less of a break than females. Females are usually rounder and show a bigger break.
In captivity, most species thrive where the humidity is kept constant at 80-100% and where the temperature is around 75-80 F degrees (24-27 °C) during the day and no lower than 60-65 F degrees (16-18 °C) at night.
Captive poison dart frogs are sometimes confused with Mantellas, a small colorful frog only found on the island of Madagascar. These two families of frogs are not closely related and Mantellas typically prefer cooler temperatures, are non-poisonous and usually smaller in size than the medium to large species of poison dart frogs.
[edit] Color morphs
Some species include a number of sub-species 'morphs'. Typically different morphs represent geographically separated populations of the same species in the wild, showing different coloration characteristics. For example, D. tinctorius includes at least a dozen color morphs, including "Surinam Cobalt", "Inferalanis", "Powder Blue", "Patricia", "Regina", "Giant Orange", and others; although a few varieties may be the result of cross-breeding by domestic owners, rather than 'true' morphs found in the wild.
[edit] References
- Amphibian Species of the World - Dendrobates, Cope, 1865. Retrieved on 2006-11-09.
- Grant, Taran; Frost, Darrel R.; Caldwell, Janalee P.; Gagliardo, Ron; Haddad, Celio F.B.; Kok, Philippe J.R.; Means, D. Bruce; Noonan, Brice P.; Schargel, Walter E. & Wheeler, Ward (2006): Phylogenetic systematics of dart-poison frogs and their relatives (Amphibia, Athesphatanura, Dendrobatidae). Bulletin of the American Museum of Natural History 299: 1-262. PDF fulltext
