Terror in Black and White

Natural History, Dec, 1998 by Robert L. Pitman, Susan J. Chivers

Killer whales devastate a pod of sperm whales in the Pacific off the coast of California.

We sit silently in the galley waiting for the sun to rise on another day at sea. Vibrations from the ship's engines cause concentric circles to jiggle in our coffee cups, and we stare at them, mesmerized. Attention is easily corralled at five in the morning.

Our meditations are interrupted by a phone call from the wheelhouse, with a report that killer whales are attacking sperm whales in front of the ship. We hesitate. The crew is sometimes merciless with its practical jokes, and the scientists on board are easy prey. We are here to study the diving habits of sperm whales, but we have spent a luckless two weeks off the coast of central California on the David Starr Jordan, a research vessel of the National Oceanographic and Atmospheric Administration (NOAA). Late yesterday, about seventy miles off the coast, we finally sighted a group of whales; and we are, as the crew knows, eager to relocate them. So it is not without skepticism that we gather our coffee cups and make our way up to the flying bridge. Moments later, we are focusing our binoculars on a group of sperm whales rafting close together at the surface. They are surrounded by a large slick, the kind that forms when oil from exposed blubber seeps to the surface. Even in the dim light, we can see a large and widening circle of blood.

As our eyes adjust to the light, we witness a sight that few who study whales have ever seen. Nine sperm whales have gathered to form a "rosette," their heads pointing to the center, their bodies radiating out like the spokes of a wheel. Sperm whales, like musk oxen, are known to "circle the wagons" in the face of imminent danger, but whereas musk oxen always face outward with their horns toward their attackers, sperm whales form a ring with their tails out--the tail of a large whale being a formidable weapon. The reason for the defensive formation quickly becomes apparent: three or four adult killer whales are rapidly circling just outside the rosette.

From their relatively small, backward-curving dorsal fins, we can see that the killer whales are females (the dorsal fins of adult males are giant and triangular). At least two of the females are accompanied by young calves, which leap alongside their mothers like frisky pups.

A killer whale in attack mode is a strangely contradictory sight; the consensus among us is that with its striking black-and-white pattern and aggressive demeanor, it looks like a shark in a clown costume. But this group of killer whales is here on business. One of the adults charges into the rosette, arches, and broadsides a sperm whale, hitting it hard below the waterline. The wound she inflicts must be serious, because fresh blood wells up to the surface of the water.

Next, for no apparent reason, the killer whales abruptly dive and leave the scene. The sperm whales, however, continue to hold their formation. Soon, four female killer whales come charging in, this time from about a quarter mile out. At one hundred yards, they lunge high out of the water, shoulder to shoulder, in the synchrony of practiced pack hunters. Circling rapidly around the rosette, they stay just beyond the reach of those dangerous tails. One cuts in and locks her jaws onto the side of a sperm whale. We can see flashes of white below the surface as she spins around, tail pumping, trying to wrest a mouthful of flesh. As fresh blood again colors the surface, two more killer whales join the attack. After a brief flurry, the attackers again retreat and the sperm whales shore up their formation. From our vantage point, the sperm whales appear to be holding their own. But the air is filled with the smell of flesh and oil, and they huddle in a gathering cloud of their own blood, which hints at the unseen damage below.

Curiously, although killer whales are believed to prey regularly upon larger whales, only a handful of recorded observations exist. And these eyewitness accounts are lacking in detail--probably because most of the action takes place underwater. Consequently, almost nothing is known about how these attacks are orchestrated, what the responses of the prey are, or even how prevalent such encounters really are.

Although we are scheduled to move out of the area, this rare opportunity cannot be ignored. We watch for three hours as the female killer whales and their excited young return again and again to press their attack. The rest of the herd, including two or three adult males, are scattered up to a mile or so away. The strategy of the attackers seems to be to wear down their much larger prey--to wound them, withdraw and let them bleed for a while, and then charge again. Whenever the killer whales withdraw for a little longer than usual, individual sperm whales briefly pull away from the rosette, roll on their sides, or hang head-up or tail-up in the water, perhaps looking for signs of the predators' return.

The sperm whales we are observing this morning are probably adult females, judging by their size. Smaller than males, they are still considerably larger than their aggressors (about thirty-three feet versus twenty-one feet) and much heavier (approximately thirteen tons versus four tons). They can, with a flick of that giant tail, inflict a fatal blow. Even a broken jaw can cut short the roughly sixty-year life span of a killer whale.