The Giant Australian Cuttlefish, Sepia apama, is the largest cuttlefish in the world. Fully grown, they can reach half a meter in overall length and weigh in at up to 11kg.
Solitary animals, they live all round the coastline of the southern half of the Australia. All the way from Central Queensland on the east coast. Right around the bottom of the continent and up to Ningaloo Reef in Western Australia.
Giant cuttlefish are incredibly photogenic creatures that can almost instantly change their color and skin texture. A capability they use to great effect as camouflage when they are hunting or being hunted. To communicate with other cuttlefish. And, most importantly… as part of their amazing courtship displays during the mating season.
They are also remarkable intelligent animals that are said to have the largest brains of all marine invertebrates.
Both male and female cuttlefish have relatively short life cycles of one to two years. And interestingly they have two alternate development cycles. With the first group going through a “growth spurt” in their 7 to 8 months to reach maturity by their first summer. Which means they are ready to mate at the start of winter.
The second group has much slower growth. And, as a result 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 that it’s nature’s way of hedging bets. So if a catastrophic event occurs one year, there is a backup population that can still breed the following year.
As winter approaches the cuttlefish will abandon their solitary lifestyle. And start to aggregate 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 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. At Whyalla however you only have to walk in off the beach and the cephalopod version of Sodom and Gomorrah is all around you!
Distinguished marine biologist Roger Hanlon, of the Woods Hole Oceanographic Institution, called it the “the premier marine attraction on the planet”.
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