Marine scientists are gaining a better perspective on why pilot whales periodically run themselves aground en masse. The scientists are also experiencing some success in rescue efforts. The effort to help 58 whales that stranded themselves on a Cape Cod beach last week has shed some light on the phenomenon.
``From our direct experience in five previous stranding events, we are seeing some patterns emerging,'' says Greg Early, biologist and assistant curator of the New England Aquarium in Boston.
``The last stranding occurred because a group of mainly females and calves were aggressively foraging for food in a high-risk area,'' he said. These factors, compounded with the quirky geography of the Cape, an unusually high tide, and gale-force winds, apparently caused the whales to make a navigational error.
``In conditions like that, a very small mistake can be disastrous,'' said Mr. Early. ``We don't know what that mistake was.
``The herding instinct that helps them survive together at sea works against them in a panic situation,'' he added.
Early explained that the strandings of the last five years on the New England coast have fallen into two categories. One seems to occur in late fall or early winter and involves whales of both sexes and all ages. The second stranding event seems to occur later in the season; it has involved smaller numbers of whales, primarily females and calves.
Marine biologists at the New England Aquarium hypothesize that this second group forages in areas where other sea mammals will not go, seeking extra food to nourish the sometimes-pregnant females and the calves that comprise the pod (group).
Cape Cod Bay is a natural trap, with no eastern access to the open sea.
The New Zealand coast is another trouble spot, with frequent recordings of mass whale beachings (nearly 300 in August 1983).
This puzzling phenomenon has been occurring for centuries. Theories abound as to the cause, but no single piece of evidence has linked all recorded strandings. Possible causes put forward include:
A sick leader or pod member heads to shore, and other whales follow.
Gently sloping beaches distort the animals' sonar systems, thereby disorienting them.
Parasites in lungs, trachea, inner ear and heart disrupt the normal behavior of the sea mammals.
Once terrestrial animals, the whales seek land under stress.
Controversy continues as to whether rescue of the whales should be attempted and, if so, how to do it. The successful rescue of three young male calves from last week's stranding and their transport to the New England Aquarium is cited as evidence that progress is being made. The young whales are being kept in a 60,000-gallon tank, where they are fed and monitored. Two appeared to be doing fine Wednesday, said Early, but the third and smallest was not eating much.
In most strandings, the event is not detected until the whales have run aground. Now, says Early, ``with the extensive networking we have established with local coastal residents and marine groups, we can try to avert the event, as we did last week.''
However, the attempts by scuba-clad swimmers and volunteers did not succeed in redirecting the whales out to sea. Twenty-six of the 58 stranded whales died, and over a dozen are unaccounted for.
There is a debate among specialists about when a beached whale should be put to sleep by injection, a standard practice in strandings. Marine biologists and whale-preservation groups use varying criteria in deciding when a whale is beyond help.
Joseph Geraci, the aquarium's research veterinarian, is considered an expert on whale strandings. He asserts that as soon as a whale has run aground, its system begins breaking down, the animal goes into shock and soon thereafter, euthanasia is usually ``the most humane solution.''
Robbins Barstow, volunteer executive director of Cetacean Society International in Wethersfield, Conn., says biologists in New Zealand and Australia have managed to return stranded whales to sea successfully. ``One New Zealand biologist ... has made a videotape of a stranding of 30 to 40 whales that were returned to the sea successfully, without evidence of later stranding,'' said Mr. Barstow.
The New Zealander's methods have included getting the whales into holding areas of shallow water, having volunteers help ``stabilize'' the whales for an extended period of time, and then drawing the apparent leaders out to the sea and turning them to face the pod. The whales apparently followed the leaders to the open sea.
Barstow says that the rescue of the three calves last week was due, in part, to a merger of methods. A pontoon used by Early and other volunteers to tow some of the whales out was manufactured by a New Zealand whale group.