It’s difficult to imagine anything attacking the great white shark (Carcharodon carcharias), but new evidence has revealed that’s exactly what squids in the eastern North Pacific Ocean have been doing. Photos published as part of a study in the journal Nature have revealed the less-than-friendly run-ins great whites have been having with squid in the waters of Guadalupe Island, Mexico. Researchers found 14 sharks with evidence of injuries from squids in the form of scars, most of whom were young males and perhaps easier to take on.
Using non-invasive techniques, the team kept an eye on the sharks from August to December in 2008, 2012, 2013, 2017, and 2019. During one season they noticed that a male had new scars, demonstrating that the attacks couldn’t be happening far from the waters of Guadalupe Island where the team was based.
Such interactions aren’t new and evidence of squid attacks on sharks have been seen across the globe. Cephalopods, a group of marine animals including squid, octopus, cuttlefish, and nautilus, make up around 50 percent of some shark species’ diets. As such, injuries from squid-shark interactions likely came about in a hunting attempt, revealing that sharks with scars are utilizing the twilight zone, where squid are mostly found, for feeding.
“The consumption of cephalopods could be essential in the diet of the white shark by allowing a quick digestion and absorption due to the large amount of proteins and low lipid content present in this group of invertebrates,” wrote the study authors. “In addition to the protein content, it has been suggested that some cephalopod species such as D. gigas contain high contents of essential fatty acids for shark reproductive processes, such as gonadal maturation and embryonic development, which could favour spermatogenesis in subadult males and pregnancy in adult females.”
It’s not unusual for great whites to sink to such depths in search of a meal and heading for the Twilight Zone where sunlight can’t follow is a common behavior in subadult and adult sharks. This layer of water is a popular depth for squid, sitting around 200 to 1,000 meters (650 to 3,300 feet) below the ocean’s surface.
“The fact that squid cause these marks on sharks suggests an extremely aggressive encounter between predator and prey, in which the defensive scars protrude on the head, gills and body of the white shark,” wrote the authors. “The suction power of the arms and tentacles of large squids is likely to deform the structure of the shark dermal denticles and hence the scars, and in some cases generate open wounds depending on the intensity of t