The southern blue-ringed octopus (Hapalochlaena maculosa) is one of three (or perhaps four) species of blue-ringed octopuses. It is most commonly found in tidal rock pools along the south coast of Australia. As an adult, it can grow up to 20 centimetres (8 in) long (top of the mantle to the tip of the arms) and on average weighs 26 grams (0.9 oz). They are normally a docile species, but they are highly venomous possessing venom capable of killing humans. Their blue rings appear with greater intensity when they become aggravated or threatened.