Kokoe poison frog
– Also known as poison dart frog
– The frogs excrete the poison: batrachotoxin
– About 136 micro grams is a lethal dose
– One frog has about 1100 micro grams
– It affects nerve and muscle cells resulting in cardiac failure
– Believed to be the poison that killed navigator Ferdinand Magellan
When touched or threatened, poison dart frogs (found in the Amazon in South America) produce venom from glands behind their ears on their backs. Traditionally, indigenous people have used the venom for blow darts.
The poison, Batrachotoxin, is extremely toxic, with only 136 micro grams required for a lethal dose for a person weighing 68kg (or 150lb). That’s about the same as 2 grains of table salt. One frog has enough poison to kill an average human 8 to 10 times.
The toxin interferes with the nerve and muscle cells of the body, basically opening them so a lot of sodium ions flow into the cell, making the muscles contract and ultimately causing cardiac failure. There is no known cure. The frogs themselves have a modified sodium channel protein so the toxin can’t bind to a receptor.
What is fascinating, is that captive-born frogs are not poisonous, which suggests the poison comes from their diet. The food source has been determined as a beetle, but it was discovered by an incident on the other side of the world, in Papua New Guinea when it was discovered a Pitohui bird had the same toxin in its feathers (although not at the same strength). You can watch the short video below to hear that story (it’s really interesting and only goes for 1min 48sec).
It would be really rare for a beetle to synthesise a molecule like batrachotoxin, so it is thought they also get it from their diet, possibly arthropods or plants.
Batrachotoxin is thought to have been the cause of the death of Ferdinand Magellan (the Portuguese explorer who organised the Spanish expedition to the East Indies from 1519 to 1522, resulting in the first circumnavigation of the Earth, which was completed after his death). There was an attack with local tribal people in the Phillippines and Magellan was struck by a poisoned arrow and left to die by his retreating comrades.