Terror in Black and White

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

The battle has reached its peak. Several sperm whales have been dragged away from the rosette and are being savagely attacked. One of the largest rolls slowly over on its side like a sinking ship and appears to be very near death. Then, as if on cue, a bull killer whale rushes in. He broadsides the isolated sperm whale, pushing it side-ways through the water. Like an angry dog, he seizes it by the flanks and shakes it violently from side to side, then swings it around in an arc, throwing up huge sprays of water. As he jerks his head to tear off chunks of flesh, his turgid dorsal fin quivers with intensity. The actions of the female killers have been demure compared with the power exhibited by this animal.

Just as abruptly as it began, this final assault ends, and a calm sea covers up the evidence. The bull slips away, dragging the dead sperm whale with him. Our vessel moves slowly through the area of the kill; we pick up a forty-pound chunk of floating blubber from the slain whale. Back at the lab, using molecular genetic techniques, we will confirm that the victim was a female. Sperm whales are thought to have a matriarchal social system; this individual may have been mother, daughter, or sister to the others in her group.

After the coup de grace and exit of the bull, the females and their young leave the area. We see the dead sperm whale one last time when a group of four or five killer whales bring it briefly to the surface. Towing it backward through the water, they quickly distance themselves from the remaining sperm whales. A giant tail, once lifted out of the water in majestic arcs at the start of hour-long dives, now dangles awkwardly over the heads of the victors.

A pod of whales that may have spent decades traveling the North Pacific together has been devastated. Instead of targeting a specific individual during the attacks, the killer whales appear to have attacked at random. As a result, every member of the herd has been injured, and all may die from wounds received this morning. One has been disemboweled, its intestines draped over its back and floating alongside. Another rolls over close to our ship; hanging from its side is a huge, yawning slab of blubber, perhaps eight inches thick and as trig as a queen-size mattress. The attackers had been skinning this whale alive. The killer whales killed more this morning than they could possibly eat: hundreds of tons of flesh are left behind. We are struck by the tremendous waste. Leaving the remaining sperm whales, we silently watch them still trying, with little apparent success, to form a rosette as they disappear in our wake.

A mile or so from the kill site, we rejoin the killer whales and photograph them for an hour as they dive, presumably feeding on a carcass well below the surface.

What we have seen is probably the most dramatic killer whale attack on a large whale species ever witnessed by scientists. Although it has provided new insights into the dynamics of killer whale predation, it has also left many unanswered questions. For example, how important has killer whale predation been in shaping the life-history characteristics of large whales? Before witnessing this encounter, we--like others in the field--believed that sperm whales, because of their size, cooperative herd behavior, and deep-diving proclivities, were largely exempt from the pressures of predation by killer whales. Also, why were these sperm whales so passive in the face of attack, and why did they stay together and, in some cases, risk their lives to come to the aid of others in their group? Many individuals might have escaped harm by diving and leaving their wounded companions behind.