GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) breeding males posturing. Spencer Gulf, Whyalla, South Australia

GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) pair mating. Spencer Gulf, Whyalla, South Australia

GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) male. Spencer Gulf, Whyalla, South Australia

GEORGETTE DOUWMA / Two giant cuttlefish (Sepia apama) males in display combat over an egg-laying female. Spencer Gulf, Whyalla, South Australia

GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) male guarding egg-laying female. Spencer Gulf, Whyalla, South Australia

GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) male guarding female resting between bursts of egg-laying. A rival male is in the background. Spencer Gulf, Whyalla, South Australia

GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) fighting. Spencer Gulf, Wayalla, South Australia.

GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) males displaying while guarding their females to ward off other males, Spencer Gulf, Wayalla, South Australia. The female they are fighting over is actually decapitated...

GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) male camouflaged next to rock with algae, keeping an eye on the female in the background. Spencer Gulf, Wayalla, South Australia.

GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) mating. Spencer Gulf, Wayalla, South Australia.

GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) male at rest. Spencer Gulf, Wayalla, South Australia.

GEORGETTE DOUWMA / Giant cuttlefish (Sepia apama) in display combat when mate-guarding males get too close to each other: pulsing dark stripes along their bodies. These ritualised displays are usually enough to deter we...