Giant Australian Cuttlefish

IUCN

Scientific Name：Sepia apama

Basic Information

Scientific classification

name：Giant Australian Cuttlefish
Scientific Name：Sepia apama
Outline：Mollusca
Family：Sepiidae Sepia

Vital signs

length：Mantle to ~50 cm; total length ~1 m
Weight：Very large individuals ~10 kg
lifetime：About 1–2 years; post‑spawning senescence

Feature

Millisecond camouflage & papillae; winter spawning aggregations; strike tentacles; buoyancy via cuttlebone.

Distribution and Habitat

Temperate S Australia—reefs, seagrass, sand/gravel (1–50+ m); iconic Whyalla aggregation.

Appearance

Broad body, continuous lateral fin; 8 arms + 2 tentacles; large eyes with W‑shaped pupil; roughened skin when papillae raised.

Details

Sepia apama, the Giant Australian Cuttlefish, is among the largest cuttlefish (order Sepiida, family Sepiidae). It is famed for millisecond colour/texture change and erectable papillae that sculpt the skin, enabling superb camouflage and vivid courtship displays. The winter spawning aggregation in South Australia’s Spencer Gulf is world‑renowned.

Ecology & Biology

Diet: fishes, crustaceans and polychaetes; prey seized by two strike tentacles and processed with a beak.
Reproduction: adults migrate in winter to shallow reefs to mate; males display high‑contrast patterns and compete; females glue egg clusters into crevices and algae.
Behaviour: capable learners; deploy dynamic bands, checkerboards and passing waves according to background and rivals.

Identification

Possesses a large internal cuttlebone for buoyancy; broad body with a continuous lateral fin.Eight arms + two tentacles (tentacles retracted into sheaths), large eyes with a characteristic “W‑shaped” pupil; skin papillae can be raised for a rough, nodular appearance.

Size & Longevity

Length: mantle up to ~50 cm; total length approaching 1 m.
Weight: very large individuals may reach ~10 kg (regional variation).
Life: typically 1–2 years; senescence follows spawning.

Range & Habitat

Temperate southern Australia (WA–SA–NSW), on rocky reefs, seagrass and sand/gravel from ~1–50+ m. The Whyalla nearshore of northern Spencer Gulf hosts the iconic aggregation.

Conservation & Threats

Threats: coastal development and discharges, fishing/bycatch, tourism disturbance, habitat loss and ocean warming.
Management: seasonal closures/speed limits/diving codes at core spawning sites; water‑quality monitoring and “no‑touch” guidelines.

IUCN: for site consistency this entry is marked Not Evaluated (NE) (refer to latest authoritative assessments for updates).

FAQ

Q1. How do they change colour so fast? By controlling chromatophores, iridophores and leucophores, plus raising papillae to alter skin texture.

Q2. How to tell cuttlefish from squids and octopuses? Cuttlefish have a large internal cuttlebone and a continuous lateral fin; squids are more arrow‑shaped with terminal fins; octopuses lack an internal shell and have eight arms only.

Q3. Why winter aggregations? For spawning; males perform dramatic displays and females cement eggs in crevices.

Q4. Are they dangerous? Saliva contains enzymes and mild toxins for subduing prey; not comparable to blue‑ringed octopuses in human risk—avoid handling.