Image by Albert Kok.

During the day, most octopus hide in lairs or bury in the seabed.

They emerge at night to feed, preying mainly on shellfish and crustaceans. Most octopus live for only 12 – 18 months and breed only once during their life. Males die within a few months of mating. In some species, the female octopus can keep the sperm alive inside her for weeks until her eggs are mature. After they have been fertilized, the female lays about 200,000 eggs. She hangs these eggs in strings from the ceiling of her lair or individually attaches them to the substrate depending on the species. The female cares for the eggs, guarding them against predators, and gently blowing currents of water over them so that they get enough oxygen.

A typical octopus has a hard beak, with its mouth at the center point of the arms. Most have no internal or external skeleton, allowing them to squeeze through tight places. Octopuses are highly intelligent, probably the most intelligent of all invertebrates. For defense against predators, they hide, flee quickly, expel ink, or use color-changing camouflage.