At constant dusk, the mesopelagic hunts a silent predator.
The mysterious giant squid is rarely observed in its natural habitat. In the first videos of their kind, marine scientists captured his hunting behavior in the wild – for the first time revealing how this monster with a deep stem attacks its prey.
Although the pressures and darkness of the ocean depths are hostile to us people breathing in the air, thanks to the wonders of robotic technology, we have slowly but surely learned more about them. However, most of our underwater vehicles are best suited for studying slow or immobile organisms.
For giant squid, bright lights mounted on underwater vehicles can be uncomfortable for their sensitive eyes in low light, which can grow to the size of plates; sound and vibration can also scare more mobile animals. And of course, bringing giant squid to the surface does not record their behavior in their natural habitat.
That’s why a team of scientists led by Nathan Robinson of the Oceanographic Foundation in Spain came up with another solution: a passive deep platform equipped with a camera. Because the eyes of giant octopuses are optimized to see shorter wavelength blue light, they used longer wavelength red light that will not bother them to see the animals in the video.
Finally, they added bait: fake jellyfish called E-jellies, equipped with lights that mimic the blue flashing bioluminescence emitted by atoll jellyfish (Atoll of Wyville) in need. Although it is not known that giant octopuses specifically consume jellyfish, they can be attracted by the emergency lights of these atolls – they can mean that jellyfish are attacked by something does want to eat.
So all that remained was to wait. And it paid off: at depths between 557 and 950 meters in the Gulf of Mexico and in Exuma Sound near the Bahamas, the team’s platform recorded several encounters with a large octopus.
The first encounters were in 2004 and 2005 with two large animals that may have been Promachoteuthis sloani, with a mantle length of 1.0 meter – a species that was previously known only from small juveniles.
The team continued to update their platform and captured Pholidoteuthis adami, with a mantle length of 0.5 meters, in 2013. In 2019, they finally filmed Architeuthis dux, a giant squid itself that moves in a mantle length of 1.7 meters (this does not include tentacles).
Interestingly, the encounters strongly suggest that octopuses are visual hunters and ignore the olfactory bait that has been placed nearby in favor of visual signals.
Probably the most fascinating was the hunting behavior of the giant squid. He followed the platform for about six minutes before the attack, indicating that he was chasing his prey before moving to kill.
This contradicts the assumption that giant octopuses are invaded by predators, as has been reported in several documents. Rather, the animal appears to be an active and engaged hunter who uses visual stimuli (and his humongous eyes, down there in the dark) to find food.
Each of these meetings, although few, also provided new information on the extent and distribution of the species observed.
This suggests that passive platforms can be extremely useful tools for observing these elusive creatures, especially if they are improved and optimized for specific encounters, the researchers said.
“We recommend that future studies assess the importance of using low light systems or optical baits in a more scientifically robust manner.” they wrote into their work.
“For example, while E-Jelly mimicking bioluminescence appears to be an effective tool for attracting cephalopod species, future studies could assess whether baits of different intensities, colors, or light patterns differ in their ability to attract different taxa of deep-sea cephalopods. “
The research was published in Deep Sea Research Part I: Oceanographic Research Papers.