The Giant Australian Cuttlefish, Sepia apama, is the largest cuttlefish in the world and can reach half a metre in total length and weigh in at up to 11kg.
Solitary animals, they are found all round the coastline of the southern half of the Australia – from Central Queensland on the east coast, all the way around the bottom of the continent and up to Ningaloo Reef in Western Australia.
Incredibly photogenic creatures, they have a fascinating ability to rapidly change their color and skin texture, which they use to great effect as camouflage when they are hunting or being hunted, to communicate with other cuttlefish and as part of the amazing displays they use to impress potential partners during the mating season.
The Giant Australian Cuttlefish are also remarkable intelligent and are said to have the largest brains of all marine invertebrates.
Both male and female cuttlefish have relatively short life cycles of 1-2 years and interestingly they have two alternate development cycles, with the first using a “growth spurt” over 7 to 8 months to reach maturity by their first summer so they are ready to mate at the start of winter.
The second cycle involves much slower growth where they don’t reach maturity until they are in their second and final year.
Although not scientifically proven, the most probable reason for the alternate cycles is it’s nature’s way of hedging bets, so that if a catastrophic event occurs one year, there is a backup population that can still breed the following year.
Giant Australian Cuttlefish – Nature’s Swingers…
As winter approaches the cuttlefish abandon their solitary lifestyle and aggregate together in small groups of up to 10 individuals to mate – everywhere that is except at Whyalla in South Australia’s Spencer Gulf, where tens of thousands of them gather during the annual Giant Australian Cuttlefish aggregation.
The technical term for how Giant Australian Cuttlefish mate is polyandry – which basically means multiple partners, but a more accurate term would be “spectacularly promiscuous”…
The reality is that you would have to be quite lucky to stumble upon a typical mating aggregation, but at Whyalla’s aggregation you literally only have to walk in off the beach and the cephalopod version of Sodom and Gomorrah is all around you!
It has been called the “the premier marine attraction on the planet” by distinguished marine biologist Roger Hanlon, of the Woods Hole Oceanographic Institution.