Family of Scientists on Yearlong Quest to Probe Secrets of Sperm Whales : Marine biology: Little is known about the behavior of these strange, elusive animals--which can dive more than 2 miles: how distant tribes relate to each other, or the purpose of the peculiar clicking sounds they make.

An adult male sperm whale can outweigh 10 elephants and would be able to see over a six-story building if it stood on its tail.

Its massive forehead contains an exceedingly fine oil, mistaken by early whalers as sperm, that was once used to lubricate Soviet space vehicles.

The sperm whale, relentlessly hunted in the 19th Century for its oil, still roams all of Earth’s oceans, its numbers now estimated at 1 million.

But little is known about the behavior of these strange, elusive animals--which can dive more than 2 miles: how distant tribes relate to each other, or the purpose of the peculiar clicking sounds they make.

A family of scientists, including their two small children, are midway through a yearlong voyage in a 41-foot sailboat to revisit the 19th-Century Yankee whaling grounds in the South Pacific and to explore the family secrets of the whales.

“We will examine the geographical variation in genetic structure and vocalization repertoire of the sperm whales of the South Pacific,” said marine biologist Hal Whitehead of Nova Scotia’s Dalhousie University.

“Most of the people who have studied sperm whales have chosen areas near islands where it gets deep very quickly, such as the Galapagos,” said Peter L. Tyack of the Woods Hole Oceanographic Institution. “But sperm whales are basically deep-sea animals, and the best place to study them is in the deep sea.”

Whitehead and his wife, fellow marine biologist Linda Susan Weilgart, sailed down the coast of South America, then headed into the open South Pacific--through French Polynesia, American Samoa and other islands. After a stopover in New Zealand, they will sail back to the southern tip of Chile and cruise up the South American coast, returning to Nova Scotia in the spring.

Aboard their custom-built research cutter, Balaena, they are accompanied by their son, Benjamin, 5; 15-month-old daughter, Stefanie, graduate student Nathalie Jaquet and a nanny.

The sperm whale became an American cultural icon through Herman Melville’s classic, “Moby Dick.” Melville described the animal, which belongs to a family of toothed whales, as “the most formidable of all whales to encounter, the most majestic in aspect.”

Because of its famed evasiveness, Melville’s 1851 description of the whale is still largely true: “Far above all other hunted whales, his is an unwritten life.”

All commercial whale hunting has been banned under a 1986 international agreement. But some whales still are being killed for scientific purposes. Critics have accused Japan, Iceland and Norway of violating the ban by killing excessive numbers under the guise of research.

Whitehead, whose work is supported partly by the National Geographic Society, is a pioneer of “benign research” techniques, designed to spare the lives of whales and to interfere as little as possible with their behavior.

Having the largest brain of any living creature, sperm whales, like humans, use a remarkably complex range of vocalizations.

Also like humans, whale parents care for their young for long periods. Adult whales cuddle their calves--and each other--by mouthing with their jaws, as though kissing.

Scientists have speculated that the clicking patterns of sperm whales, called codas, may be forms of communication, or mating calls, or a kind of sonar used to locate objects in the water--or all three.

It’s even been suggested that the sounds may be used to stun prey, which could account for how the leviathans catch their dinners of fast-moving fish and squid.

One mystery is whether all sperm whales throughout the world share a common language of codas, or whether distant groups have different vocabularies. If the latter is true, researchers postulate that contact between groups would be limited, and this would be reflected by marked genetic differences among the various populations.

Whitehead is collecting sloughed skin samples of whales for analysis of mitochondrial and nuclear DNA, to find out if there are major variations.

Renowned among fellow whale researchers for his seamanship and ability to handle disasters, Whitehead has so far reported smooth sailing.

“The kids are loving it,” said Dalhousie graduate student Mary Dillon, who talks to Whitehead periodically by radiotelephone from Nova Scotia. “The 5-year-old has seen all kinds of dolphins and manta rays, and he’s been in the water snorkeling, having a great time.”

As for the toddler, Dillon reports: “She’ll actually be learning to walk on a boat.”