Sandia LabNews

Pop-off instrument packet helps study, track giant blue whales through the wine-dark sea

The word "predator" conjures up images of a jagged-toothed feline on the African plain. But the world’s largest predators carry out their carnage far from the watchful eyes of trained observers.

Eating up to two tons a day, blue whales cruise the world’s oceans, diving down to 100 meters to feed on krill and other small crustaceans they filter from the ocean water. These endangered animals — as long as three school buses and as heavy as 50 elephants — dwindled in number an estimated 97 percent by the time whaling stopped in 1966. After resurging locally in the 1990s, there are now some 2,000 blue whales off the coast of California, and perhaps 12,000 worldwide.

Marine biologists at the University of California at Santa Cruz who spend their careers tracking these creatures’ elusive and mysterious habits received a little help not long ago from Sandia. The scientists had tried to modify a pager to create a radio tag to track the cetaceans. A colleague at the Naval Postgraduate School in Monterey suggested they contact Sandia for assistance. With $5,000 provided through the Small Business Technical Assistance program, the biologists received a matchbox-sized receiver that makes their data logger pop off automatically in response to a signal, much like a garage door opener functions by sending a digital code.

The scientists were overjoyed with this advance that permitted them to recover the flashlight-sized, buoyant orange data loggers (each worth $2,500) when they were in the vicinity during calm seas. Previously, they had relied upon a corrodible magnesium link that breaks apart over time, releasing the data pack to send out a locator signal. Recovering the data loggers had been time-consuming and uncertain — some never were found.

Bearing a time/depth recorder (about the size of a deck of cards), the data logger also records light level. Once the retrieved data logs were downloaded onto a computer, the light levels and clock signals together revealed, roughly, where the whale had traveled — by indicating day length (latitude) and time of day (longitude). A pressure sensor, meanwhile, revealed depth of dives, while a resistance detector logged when the whale had surfaced above the waves.

The scientists received a research permit to tag the whales, who carry the data logger embedded by a thumb-sized barb in their skin for a couple of weeks. Penetrating about an inch, the barb does not extend past the skin into the whale’s blubber layer. It is eventually sloughed off much the way a person’s skin will thicken and heal beneath a splinter.

"The whale doesn’t even know it’s there," says Jamie Stamps (8111), an electrical engineer who received a patent for design of the releasable device. He built about 10 copies for the researchers to assist their studies of whale feeding behavior. The devices were also used by scientists at the Southwest Fishery Science Center in La Jolla and the Marine Mammal Center in Sausalito. Jamie also fielded inquiries from the Canadian Fisheries and National Geographic Television.

One bottleneck in creating the final device was acquiring an integrated receiver that was only intermittently available from distributors, he says. Other aspects were fairly straightforward. A couple of AA batteries powered the devices for a month. Dick Jones (8414), who had experience with high-reliability valves, also assisted the work, helped locate a low-power wire cutter that could be activated by small batteries. Dick and Jamie also sketched out plans to create a spring-loaded device that could be reset, which would spare the cost of the non-reusable wire-cutter (each runs $180).

Coupled with video from cameras mounted by corrodible suction cups to the marine mammals, the data logs are revealing a story of animals who must be as efficient as athletes to capture their prey and thrive, says UCSC marine biologist Terrie Williams. Studying Weddell seals and blue whales, she observed the animals conserving a surprising degree of energy during dives, essentially dropping like a stone, then propelling and gliding back to the surface. Williams says it took a bit of ingenuity to discern any motion of the blue whales — she couldn’t detect any change in hours of tape until she increased the speed by a factor of seven. "These are the largest creatures in the world, and I had to get down to whale speed," she says.

Part of the story she expects to emerge shortly involves blue whales’ only natural enemy, orcas — or killer whales — who can hunt in packs and, being warm-blooded, require more food than predators like sharks. Salmon and other rich fish that are a food of choice for orcas have been vastly depleted. Sea otters are declining in number too — possibly because orcas have increased their intake of these mammals (Williams has photos of orcas eating sea otters). She says impacts on blue whales, however, are hard to discern since their worldwide population figures are so uncertain.