Shark Ecology 103
whaling records indicate they also eat small deep-sea sharks. Sperm whales
were also seen attacking a Megamouth Shark off North Sulawesi, Indone-
sia, the only known record of anything other than a Cookiecutter Shark
attacking a Megamouth.
On an even larger scale, whale researchers have recently discovered that
orcas (killer whales) feed on sharks around Vancouver Island, British Co-
lumbia, and farther north near Alaska. Packs of orcas gang up on sleeper
sharks (probably Pacific Sleeper Sharks) and tear them apart. One feeding
frenzy produced a large slick of floating shark meat and liver; the iden-
tity of the shark was confirmed by DNA analysis. Other observations sug-
gest that orcas attack Blue Sharks farther south. Orcas have also been seen
eating White Sharks off the California coast, with one often-seen female
orca feasting on White Sharks at the Farallon Islands, offshore from San
Francisco. Orcas have also been filmed attacking Whale Sharks, Common
Threshers, Shortfin Makos, mantas, and stingrays.
Incidents in public aquariums suggest that sharks have other enemies,
including some without backbones. Spiny Dogfish were disappearing mys-
teriously from a large exhibit at the Seattle Aquarium. Workers at the fa-
cility stayed late one night to see what was happening. They saw (and vid-
eotaped) a large giant Pacific octopus capturing and consuming a Spiny
Dogfish. Whether such predation occurs in nature, and if so, how often,
is unknown, but octopuses (not “octopi”) are intelligent animals capable of
capturing and eating a variety of prey, so it would not be surprising if the
Seattle octopus was showing its natural predatory behavior.
Not all attacks on sharks are for the purposes of feeding. Dolphins and
porpoises are reputed to ram sharks, apparently in defense of their young,
although actual observations of this are hard to find. An incident at the Mi-
ami Seaquarium in which bottlenose dolphins attacked and killed a Sand-
bar Shark during the birth of a baby dolphin may have inspired the “con-
ventional wisdom” that such events are common. In Hemingway’s The Old
Man and the Sea, the fisherman Santiago wonders how many sharks his
marlin had killed when it was alive. What Hemingway based this idea on is
unknown. A marlin being attacked by false killer whales in Hawaii speared
a diver who tried to film the event, and fishermen off Nova Scotia and New
York have observed Broadbill Swordfish turning on attacking sharks, so it
isn’t beyond reason to think that billfish may attack sharks, at least as a de-
fensive maneuver.
Better documentation exists of other fishes ramming sharks. For rea-
sons that remain mysterious, Giant Trevally (Caranx ignobilis), a relative
of pompanos and jacks, attack and kill reef sharks much larger than them-
selves but don’t eat them. Observations from the tropical Pacific (Saipan,
Mariana Islands; Palau, Western Caroline Islands; Marshall Islands) have