Learning About Giant Squid From Sperm Whale Stomachs
By looking in the stomachs of three sperm whales stranded in the Bay of Biscay, Cherel recovered hundreds of beaks from 19 separate species — 17 squids including the giant squid, the seven-arm octopus (the largest in the world) and the bizarre vampire squid. Together, these species represent a decent spread of the full diversity of deep-sea cephalopods.
He analysed the chemical composition of the beaks. and in particular, their ratio of carbon isotopes (carbon-13 compared to carbon-13) and their ratio of ratio of nitrogen isotopes (nitrogen-15 compared to nitrogen-14). These measurements are a reflection of both what and where the animals ate.
Levels of carbon-13 can tell us how deep an animal lives, whether it swims offshore or inshore, and whether it spends its time in the open ocean, or sticks close to its floor. All of the cephalopods’ carbon-13 levels fell within a narrow range, indicating that all 19 species live in similar and overlapping parts of the ocean.