These animals belong to the family of frogs Dendrobatidae.
As of August 2006 there were 247 known species of the poison frogs. They live throughout Central and South America, in different geographical structures such as streams and rainforests. (Ref. 1)
Though they can be found in a number of different habitats (such as aquatic ones for example (ref. 2)) these frogs are primarily terrestrial amphibians laying terrestrial eggs. (Ref. 3)
All of them are quite small (1-5cm long), diurnal (active during the daytime) (except for one Australian species). As we've already mentioned, many of them are brightly coloured, often with strong patterns, and toothless. (Ref. 4)
The bright colours are an important characteristic that sets the dart frogs apart from other frogs.
As Chris Hardman explains it very well:
"These half-inch to two-inch amphibians come in vibrant yellows, reds, and blues in patterns of spots, swirls, and lines. Like other poisonous creatures, bright colors tell predators to stay away and give the poison frogs an advantage over others frog species. Instead of relying on camouflage and darkness for protection, they can hop around safely during the daytime without being bothered." (Ref. 5)
The current traditional view is that around 1/3rd of the known species of the poison dart frogs secrete powerful toxins by the "poison" glands in their skins. In fact, this is how this group gained its name. (Ref. 6)
Taran Grant and his co-authors mention the fact that it was originally the Embera people of the Choco Region in Colombia who started using the poison of three most toxic species of these dendrobatid frogs for the blow-gun darts for hunting purposes. (Ref. 7) (Please note that it is only these three species of dendrobatids - Phyllobates Aurotaenia, Phyllobates Bicolor and Phyllobates Terribilis - that are used by the Embera Indians to poison their darts (ref. 8). The other species belonging to this family, are not toxic enough for this purpose).
These 1/3rd of all the species are known as "aposematic" frogs, i.e. the ones that use their strong colours and colour patters to warn their potential predators of their toxicity and therefore deter predators from attacking the frogs. (Ref. 9)
The remaining 2/3rds of these animals are assigned to "a ''basal'' grade of brown, non-toxic frogs." (Ref. 10)
But as the authors of the article state further, there is not enough compelling evidence to substantiate this split. Also it has been found in some studies that several species of the poison dart frogs that were originally assigned to non-toxic frogs are no less brightly coloured than the toxic ones, and that several other species thought to be toxic ones are actually more closely related to some non-toxic species. (Ref. 11)
We know that these amphibians get their poison from the diet of certain ants and other insects rich in toxic alkaloids which they cannot produce themselves.
"formicine ants, a siphonotid millipede, melyrid beetles, and scheloribatid mites have been identified as likely dietary sources for certain alkaloids . , but the remaining alkaloids are still unknown elsewhere in nature." (Ref. 13)
Some popular press also reported that the dart frogs consume South American fire ants which contain a strong formic acid, and thus make the frogs very toxic. (Ref. 14)
These frogs' diet is highly specialised compared to other species of amphibians (ref. 15). Our guess is that this is due to their need to consume only certain types of food that contain toxins.
In fact, one study has determined that the diets of certain toxic species of frogs from Nicaragua and Ecuador comprised 50 to 73% of ants. The non-toxic frogs under the same study had a much more diverse diet, with ants making up 12 to 16% of the diet and the rest - a variety of flies. (Ref. 16)
The most dangerous of all the poison frogs is Phyllobates Terribilis (also known as the golden poison frog) which can kill around 1,000 mice or severely disable a man.
This frog species is endangered and is currently listed in the IUCN Red List of Threatened Species.
Another interesting fact about the poison frogs is that, unusually for many species of frogs, at least some species of these frogs provide parental care for their offspring.
For example, the male of species Dendrobates Aurata can carry a tadpole on its back until the tadpole is large enough [to live independently]. (Ref. 17)
Some other species of poison frogs will protect their eggs by urinating on them if they become too dry and by keeping the predators away. (Ref. 18)
Also see how the strawberry poison frog cares for its offspring.
According to the Global Amphibian Assessment, around 28% of 234 known species of poison dart frogs are now threatened with extinction. (Ref. 19)
The main threats to these frogs' survival are the same as for other tropical frogs, which are further discussed in the Amphibian Declines article. And that is why it sounds logical to try to protect them in the context of the rest of amphibian species.
Many species of the Dendrobatidae family (specifically all the species of the Allobates, Dendrobates, Epipedobates and Phyllobates genera) are now included in the CITES Appendix II. (Ref. 20)
This means that these endangered animals "are not necessarily now threatened with extinction but that may become so unless trade is closely controlled." (Ref. 21)
|Written by:||Irina Gray of Tropical-Rainforest-Animals.com|
|Publication Date:||September 2007|