Common Octopus

Photo: Adrien F. · CC BY-NC

Common octopus reach high densities on the Amadores artificial reef where the complexity of concrete modules provides an abundance of den sites at exactly the depth and substrate type they prefer. Each individual maintains a territory centred on a den entrance decorated with a midden of empty shells — crab carapaces, bivalve halves, and sea urchin tests — that advertise the octopus's hunting success and den location. Night dives reveal their full behavioural range: active hunting, colour change communication, and jet-propulsion escapes that demonstrate why they are considered the most intelligent invertebrates on the reef.