WILD LIFE | 05.02.17
Off the coast of South Australia, an unremarkable setting conceals one of the ocean’s most spectacular events—a mating spree for the world’s largest cuttlefish.
Scanning the austere coastline surrounding South Australia’s Spencer Gulf, there would be little reason to suspect that anything extraordinary ever happens in this place. A monotonous landscape of sand, rocks, and shrubs is interrupted only by the occasional gas refinery or lead smelter. The name of the area’s most prominent landmark, Point Lowly, practically promises obscurity. But dipping beneath the surface of the Gulf’s chilly mid-winter waters reveals a different world altogether. Here, aggression, deception, and sex rule the day.
For reasons no one completely understands, Point Lowly has become the spot where the world’s largest cuttlefish—a type of free-swimming mollusk most closely related to octopuses and squids—comes to spawn en masse. In a patch of ocean roughly the size of 10 soccer fields, as many as a quarter million giant Australian cuttlefish (Sepia apama
) emerge from their otherwise solitary existence and gather to compete for mates and find suitable places to lay their fertilized eggs before they die.
At Point Lowly, researchers needn’t venture far to find their study subjects. According to acclaimed underwater photographer Justin Gilligan, who captured these images, giant cuttlefish can be found spawning in water as shallow as knee deep, just steps away from the point’s historic lighthouse—and then as far as the eye can see. The sheer abundance of animals and activity makes for an interesting predicament, says Gilligan. Typically, his challenge as a wildlife photographer is finding interesting behaviors to capture. During the giant cuttlefish spawning aggregation, it’s the opposite. With so many remarkable maneuvers and displays happening all around, the hardest part is knowing which direction to aim his camera.
To improve their chances of reproductive success, male giant cuttlefish compete with one another in a variety of ways. Size and might are two of the more obvious means of winning and keeping a mate. Large males physically guard females and nesting sites, and warn off would-be competitors with rhythmic, wave-like patterns of pulsating color generated by the same system that makes these animals masters of camouflage. If the warning goes unheeded, males escalate their defensive tactics, chasing off rivals, and, if necessary, engaging in physical battles waged with grasping tentacles and slashing beaks.
Some of these threats are easy to identify. It doesn’t take long to see that Spencer Gulf, which reaches deep into South Australia’s heartland, is anything but pristine wilderness. Industries of various types dot its shoreline. And with each new factory and mine comes an increase in shipping traffic, noise pollution, and the potential for toxic spills.
Then there is the spawning aggregation itself. For all its importance to the longevity of the giant Australian cuttlefish, concentrating so many breeding individuals in a single location—whether it’s surrounded by industry or not—is a risky proposition. One obvious threat is overfishing, and indeed, fishermen hauled cuttlefish out of Spencer Gulf by the hundreds of thousands in the late 1990s before restrictions were put in place. Then there are the hypothetical scenarios. One toxic spill, one natural disaster, at just the wrong time could be catastrophic. And these types of risks are only heightened by the cuttlefish’s short life span. The fact that individuals live less than two years means that there are simply fewer generations in reserve to repopulate after a decline.
For now, scientists remain hopeful that this fragile population will continue to thrive in Spencer Gulf, putting on a Technicolor display each year that would undoubtedly captivate anyone bold enough to brave the frigid water. “It's as if their bodies are glowing, and this is happening all over the yellow seaweed-covered seafloor,” says Gilligan, as he describes the impact of looking out at dozens of giant cuttlefish, their bodies rapidly pulsating with waves of color. “It’s quite a dramatic sight.”
ABOUT THE Photographer
Justin Gilligan is a photojournalist and marine scientist who has taken photographs and conducted research on some of Australia's most remote coral reef locations, including Lord Howe, Cocos (Keeling), and Christmas Islands. Gilligan was the recipient of the 2015 Australian Geographic ANZANG portfolio prize and the 2016 Save Our Seas Foundation's Marine Conservation Photography Grant. His work has been honored in a number of prestigious international photography competitions.
ABOUT THE Author
Steven Bedard isbioGraphic
’s Editor-in-Chief. A former field biologist who spent the early 90s chasing spotted owls and northern goshawks through the woods, he now writes and produces media about the work of scientists, instead of actually doing the scientific research—it’s way easier. Having written about archaeology, engineering, and astrophysics, he’s found a much happier place covering the living world forbioGraphic
. Follow him on Twitter @steventbedard.
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