During the recent Delta odyssey of a mother and calf, experts repeatedly acknowledged that they don't know why the pair swam about 90 miles up the Sacramento River before turning around.
Despite the widespread assumption that they were lost, officials say the two simply might have been exploring unchartered waters.
And although would-be rescuers tried various ways of reorienting the humpbacks -- even turning to the public for ideas when none of their efforts produced significant results -- the whales seemed to be the ones ultimately calling the shots.
Those urging rescuers to back off and let nature take its course were quick to point out that biologists were taking a break on the two days that the whales traveled the farthest, each time covering about 25 miles in roughly six hours.
"There are lots of theories, believe me," said Rod McInnis of the National Oceanic and Atmospheric Administration this week when asked about the creatures' unexpected progress.
Exactly how humpback whales navigate, where they travel, what their body language means -- even how many members of this endangered species remain and how long they live -- are part of the mystery enshrouding the creatures, said Jim Darling, a biologist in British Columbia who has been studying the humpbacks near Hawaii since the mid-1970s.
"Our understanding of any kind of whale behavior is very limited," he said.
The problem is that studying whales solely for the sake of it is seldom a priority, Darling said.
Most research focuses on the problems that arise when the worlds of man and whale collide -- issues such as depredation of a species, for example -- because that's the kind of work for which government grants are available, he said.
Many people assumed the Delta's recent visitors were lost because a whale sighting in that body of water is so rare, but "I don't think we know whether they're in there for some reason," Darling said.
And although baleen whales are thought to navigate by sight and sound for short distances, the fact that they migrate thousands of miles to specific locations suggests that something else is at work, too, Darling said.
"It's very unlikely they can 'hear' Hawaii from Alaska," he said.
Nor has any study definitively concluded what it means when humpbacks smack their tails against the surface of the water, he said.
Adults and babies both do it in different situations, including times when a mother and calf are resting peacefully, Darling said, so the behavior isn't necessarily a sign of stress.
Reach Rowena Coetsee at 925-779-7141 or firstname.lastname@example.org.