During the opening of one episode of Seinfeld, Jerry Seinfeld told a joke about how a nature scene– a lion hunting a gazelle– would be spun by film-makers to make you root for one side or the other: “Go, gazelle, run away!” “C’mon, lion, you have to eat!”
This piece brings the use of ever-smaller electronic tags to understand the habits and environments of animals (something I’ve found very interesting) into that joke.
In the cold, dark abyss of the Pacific lurk thousands of aptly named jumbo squid (Dosidicus gigas), aggressive carnivores up to six feet long and 100 pounds nicknamed “red devils” by fishermen.
Still, even these creatures can become prey to leviathans. The largest predators in the world, sperm whales, have a voracious appetite for squid, devouring perhaps 220 billion pounds a year or more, roughly equivalent to the entire annual harvest of all the commercial fisheries on Earth.
Yet how sperm whales hunt jumbo squid has remained a mystery.
Now, by electronically tagging both to peer at their habits up to thousands of feet underwater, scientists are discovering a deep sea version of “out of the frying pan and into the fire,” with squid that flee the relative heat of surface waters potentially finding themselves in the maws of whales.
Marine scientist William Gilly at Stanford University and his colleagues were tagging jumbo squid in the Gulf of California, also called the Sea of Cortez. By good luck, they found marine biologist Randall Davis of Texas A&M University in Galveston and his collaborators tagging sperm whales nearby.
After a dinner of tacos, beer and rum on Davis and his colleagues’ research vessel, the scientists decided to work together to be the first to electronically track deep sea predators and their prey simultaneously.
Lest it sound too much like a drunken lark– the scientific equivalent of waking up after a drunken bender and finding one’s self wearing a tattoo of a radio tracking collar– it should be said that Gilly and Davis didn’t throw the beer bottles overboard and immediately start shooting tags at whales; the tagging happened over the next few days. So what did they find?
During the day, electronic tags revealed tagged squid spent about three-quarters of their time at depths ranging from 600 to 1,300 feet, but at night, they spent at least half their time in shallower waters above 600 feet….
The electronics tags revealed whales spent three-quarters of their time ranging from 600 to 1,300 feet day and night, “whether squid are there or not,” Davis said. “Perhaps it’s the only way they can catch them, but no one has ever seen a sperm whale feeding in the wild, so nobody really knows how they capture their food.”