Each year, the small South Australian town of Whyalla becomes home to one of the most spectacular underwater events: the spawning of the giant Australian cuttlefish.
“First time you go and put your head under the water and see hundreds and hundreds of cuttlefish in this one little area, it just looks like a chaotic kaleidoscope. What the hell is going on here?” said Tony Bramley.
As owner of Whyalla Diving Services and a decades-long advocate for the Giant Australian cuttlefish, Bramley has observed the frenzied and colourful cuttlefish mating that occurs in South Australia’s Upper Spencer Marine Gulf Park for years. Once only of interest to fishermen and local scuba divers – who would spread the word to one another that “the cuttles are in” – this marine phenomenon now attracts tourists and researchers from across the world. It’s a welcome boost to the small steelworks town of Whyalla, on South Australia’s Eyre Peninsula.
A type of marine invertebrate closely related to the octopus, cuttlefish are whip-smart molluscs that can change colour and texture instantly. They’ve been known to solve puzzles, and can hypnotise their prey by turning their bodies into strobe lights, rapidly pulsing colour through their skin to distract and stun an unsuspecting crab or fish. Their camouflage skills put chameleons to shame, and have even attracted the attention of the US military, who have researched the colour-changing abilities of cuttlefish with the hopes of replicating their techniques for army use. If that’s not unusual enough, their mating behaviours are strange, to say the least.
From May to September each year, hundreds of thousands of Giant Australian cuttlefish gather in the waters just off Point Lowly, in the Upper Spencer Gulf, for the sole purpose of mating. Welcome to nature’s most flamboyant underwater sex show.
South Australian Tourism Commission
Once my eyes adjusted underwater, I realised I was surrounded by cuttlefish – and they didn’t seem bothered in the slightest to have a human watching their most intimate moments. With vibrantly pulsating rainbows of purple, orange, turquoise and pink and tentacles everywhere, it took me some time to make sense of this cephalopod foreplay, as cuttlefish have more than a few mating tricks up their tentacles.
In an environment where males can outnumber females 10 to one, competition is fierce to pass on one’s genes. In most species, size matters: large, aggressive males fight off their rivals to win the chance to mate. This is seen in cuttlefish as well, with large males known to wrestle one another for dominance in the presence of a female.
For any other species, this means the smaller males miss out. But cuttlefish aren’t like any other animal. They’ve figured out that if you want to impress a lover, you need to think outside the box.
“The smaller males have a conundrum on their hands, because they know they can’t win against these much larger males,” explained Sarah McAnulty, squid biologist at the University of Connecticut. “They have devised an alternate approach – masquerading as females to avoid the battle altogether.”
In perhaps the most fascinating mating behaviour of any species, smaller males can fade their translucent colouring and switch to the mottled maroons and whites of a female, before tucking their billowy arms up into their bodies. This makes them appear female, and as the burly males are busy fighting it out and leaving their potential partner unguarded, these “little sneakers”, as Bramley affectionately called them,” dart past them to get access to the female and then rapidly change their colouring back to male. A win for the clever underdog.
The ensuing awkward-looking, head-to-head spectacle – if she decides to mate – might make you wonder if the cuttlefish have been taking notes from an adult film. During the tangled twist of tentacles, the cuttlefish connect and the male deposits his sperm packet in the female’s mouth, using a specially designed arm known as the hectocotylus. The female then holds onto the sperm until she’s ready to lay her eggs.
The mating process including pulsating colour changes and males disguising themselves as females (Credit: Carl Charter)
