One of the most poisonous animals on Earth is the Poison Dart Frog. While only around 5cm long, the Poison Dart Frog has enough venom to kill 10 adult humans. Two micrograms of their toxin (an amount that would fit on the head of a pin) would be enough to kill a person.
The indigenous people of South America used their toxin to poison the tips of their blow darts which would kill any animal or person it hit. However, when kept in captivity the poisonous nature of the frog completely disappears.
The poison dart frog will secrete toxins through its skin if threatened, which are so deadly that any contact with humans or mammals will cause death. However, when in captivity, the frogs are no longer poisonous. This is because of their diet. The frogs eat certain species of ants as well as some beetles. These all exhibit the same type of toxins that the frogs secrete. The frogs have evolved to be immune to the effects of the toxin but will secrete them through their skin if in distress.
The toxins are gained through its diet
When one of these frogs is kept in captivity, however, their diet is often changed. The toxin filled beetles and ants are replaced by flies, mealworms and crickets – all of which are completely non-toxic. Due to not absorbing the toxins through their diet the frogs lose the ability to secrete it through their skin.
In the wild, the frogs eat ants, millipedes, mites and other arthropods that have toxic alkaloids naturally occurring in their skin. These smaller creatures biosynthesize the toxic compounds from things they eat on the forest floor, such as decaying plant material. These compounds are then transferred into the frog’s skin glands where they are stored and secreted when threatened.
There is only one known natural predator of the Poison Dart Frogs, this is the Fire-Bellied Snake. This snake has developed a natural immunity to the high levels of toxin secreted by the frog and is the only animal able to eat them!