1. Frogs Raised in Captivity Have No Toxin on Their Skin
Poison dart frogs live in the forests of Central and South America. Some species have poison on their skin, which belongs to a group of substances called alkaloids [1]. A study from 1994 found that when poison dart frogs were raised indoors in containers and fed only flightless fruit flies, no alkaloids were found on their skin [1]. This result led scientists to think that the source of the poison might be food eaten in the wild.
It is important to note that "poison getting weaker" and "poison becoming zero" are different things. The study showed that individual frogs raised in containers did not have detectable alkaloids [1]. The data does not show how quickly a wild-caught frog loses its poison over months. If food determines the poison, what happens if you raise children from wild parents with different foods?
2. Hawaii Experiment: Wild Frogs' Offspring Raised in Different Ways
Hawaii has wild populations of poison dart frogs that were introduced by humans. A university article describes an experiment where the offspring of these frogs were raised indoors and outdoors with different foods [2]. The children raised indoors, eating only crickets and fruit flies, did not have alkaloids [2]. However, the children raised outdoors, eating wild termites and other insects, had alkaloids similar to their parents [2].
In this experiment, both groups were offspring of wild parents. This makes it hard to explain the difference by parent differences alone. However, conditions other than location and food might also play a role. Note that this information comes from a university summary article, not the original research paper. Exact numbers and conditions need to be checked in the original study [2]. The experiment took place in captivity settings. So, what do wild frogs actually eat?
3. Poison Frog Relatives in Ecuador Eat Mostly Ants and Mites
In a field study of poison dart frog relatives (Oophaga sylvatica) living in forests in Ecuador, more than 80% of their stomach contents were ants and mites [3]. The same study also examined frogs that had been kept for 3 months eating only crickets and fruit flies. In these captive frogs raised for comparison, very few toxic components were found [3]. These two results overlap: wild frogs eat ants and mites, and when the food changes in captivity, the toxins mostly disappear.
The 80% figure applies to this specific species and the three populations studied. It is not a number for all poison dart frogs. Also, the document was a pre-print version published before peer review, so numbers might change after review [3]. If both ants and mites are in the stomachs, which one carries the poison?
4. Ants and Mites Carry the Same Alkaloids as the Frogs
A 2007 paper in PNAS found more than 80 types of alkaloids in soil mites living in the habitat of Oophaga pumilio [8]. Of these, 42 types were also found on the frog's skin [4][8]. This does not mean that more than half of the mite's poisons are in the frog. Since 42 out of "more than 80" is at most about 50%, there are also poisons found in mites but not in frogs [8].
Regarding ants, a report says that Pumiliotoxin, a toxic component, was found in a species of leaf-cutter ant relatives in Panama [5]. Out of about 500 specimens examined, only this ant had the component among those tested, and it was also found in the frog's stomach [5]. However, the number "500" comes from a news article [5]. Mites might be a more important source than ants, according to reports [4]. But differences exist by species and region, and the question is not settled.
5. Do Frogs Store Toxins Unchanged, or Change Them?
According to a 2003 PNAS paper, when two types of alkaloids were given to frogs, many species stored them on their skin unchanged [6]. However, three species in the Dendrobates genus changed about 80% of Pumiliotoxin (+)-251D into a stronger substance called (+)-267A inside their bodies [6].
This means frogs do not just receive poison from food; some species have the power to change its shape internally. But they do not make the poison from scratch. Another point is that the types and amounts of poison differ by species. Even within the same species, the combination of skin components differs by location [4]. This corresponds to the types of ants and mites eaten in that area [4]. If what is eaten differs from forest to forest, the poison mix on the skin might differ too. Do golden frogs with strong poison use the same system?
6. Beetles May Be the Food Behind Golden Poison Frogs' Toxin
Golden poison frogs in the genus Phyllobates have a strong poison called Batrachotoxin [7]. In New Guinea, beetles (Choresine genus, family Cleridae) have been found to be the source of poison for poisonous birds called pitohuis [7].
For South American frogs, it is thought that close relatives of these beetles are the source, but this is not confirmed [7]. Still, Batrachotoxin was not detected in the skin of P. terribilis frogs born in captivity, which aligns with results from other poison dart frogs [7]. The idea that birds and frogs, two very different animals, might both get poison from small insects shows how interesting the search for the source of poison is.
7. Check the "Food" Section at Zoos, Aquariums and in Books
If you see poison dart frogs at a zoo or aquarium, look for the "Food" section on the sign. You can do this with books too. Are the foods eaten in the wild the same as those given in captivity? If there is an explanation about poison, think about how it connects to this article's story. If not, comparing the "Food" sections can still be a clue.
Another question is: "Which is the main source, ants or mites?" The materials state that this is an unsettled question with different answers depending on species and region [4]. When visiting exhibits, check if there is a distinction between wild food and captive feed, or if poison is explained.