Asked by: Chris Jackson, Halifax
It’s all down to the method of delivery. Venoms must be injected to be effective, whereas poisons can come into contact with skin, or be inhaled, eaten or touched. So the puffer fish is poisonous if you eat the wrong part, because its liver contains tetrodotoxin, but its bite contains no toxins.
The blue-ringed octopus, however, can inject the same tetrodotoxin with its bite, so it is venomous. There is only one species of snake that is both venomous and poisonous. The Asian tiger snake has one toxin for its venomous bite, but it also stores a poison in its skin that comes from the toads that it eats.