The sperm whale and its large prey, the jumbo squid, are among the deepest divers in the ocean, routinely reaching depths of 3,000 feet or more. Now, in a new study, a team of marine scientists reports the successful tagging of sperm whales and jumbo squid swimming together off Mexicos Pacific coastthe first time that electronic tracking devices have been applied simultaneously to deep-diving predators and prey in the same waters.

The research team included principal investigator William Gilly, professor of biological sciences at Stanford University, and lead author Randall Davis, professor of marine biology at Texas A&M University-Galveston. Their results, published in the March 12 edition of the journal Marine Ecology Progress Series (MEPS), raise new questions about the diving behavior of both species.

"Sperm whales (Physeter macrocephalus) and jumbo squid (Dosidicus gigas) are both major predators that spend much of their lives in one of the worlds largest ecosystems, the mesopelagic zone [650 to 3,300 feet below sea level]," the authors wrote. "How sperm whales search for, detect and capture their prey remains uncertain."

To find out, the researchers traveled to the Gulf of California, also called the Sea of Corteza narrow stretch of ocean that separates the Mexican mainland from the Baja Peninsula.

"The central Gulf of California is a uniquely advantageous location to study the behavioral ecology of sperm whales and their squid prey," the authors wrote. "Sperm whales are abundant year-round and appear to feed heavily on jumbo squid, a species that is easily captured and amenable to tagging. To our knowledge, this is the first attempt to simultaneously study a mesopelagic predator and its prey using electronic tagging techniques."

Size matters

The jumbo (or Humboldt) squid is a large cephalopod species found only in the Pacific. A mature jumbo squid can weigh more than 100 pounds and grow mor
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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
8-Mar-2007