136 Sharks: The Animal Answer Guide
vulnerable to fishing. What they eat depends mostly on place and shark
species. Among sharks attracted to dead whales and dolphins (and humans)
are Sevengill Sharks, Tiger Sharks, and of course White Sharks; dead seals
attract White Sharks and Sleeper Sharks; Blue Sharks feed on dead squid,
as do some very deep-living species such as Velvet Belly Lanternsharks.
The classic opportunist, in terms of predation and scavenging both, is
the Tiger Shark. Tiger Sharks are efficient predators and capture other
sharks, bony fishes, crustaceans, mollusks, dugongs, seabirds, sea snakes,
dolphins, and sea turtles. But the list of items found in Tiger Shark stom-
achs reads like an ad for a yard sale: license plates, oil cans, tires, deer ant-
lers, boat parts, jewelry, clothing, tires, books, and baseballs.
Tiger Sharks also take advantage of opportunities afforded by short-
term periods of prey abundance. Best studied are Tiger Sharks that feed on
albatross chicks in the northwestern islands of the Hawaiian chain. Every
June and July, Tiger Sharks arrive at Midway Island and French Frigate
Shoals just as Laysan and Black-footed Albatross chicks are making their
first attempts at flying. Many of these first flights end quickly in the water,
where the sharks are waiting. Tiger Sharks aggregate similarly at Raine Is-
land in Australia to feed on a seasonal abundance of egg-laying sea turtles
that become stranded at low tide and die of heat exhaustion (see “How do
sharks navigate?” in chapter 5).
Recent discoveries in the Gulf of Mexico have shown that Tiger Sharks
feed opportunistically on birds much smaller than albatrosses. Songbirds
migrate every spring from South to North America. Those flying across
the Gulf of Mexico pass over a string of oil and natural gas platforms. The
platforms are lit up at night, and many birds are confused by the lights and
circle the platforms for hours until they become exhausted and fall into
the sea. This “nocturnal circulation” may involve as many as 100,000 birds
circling a single platform. Tiger Sharks have learned about this bonanza.
Nearly half of 50 Tiger Sharks caught over a two-year period near these oil
rigs contained a birdwatcher’s list of small species, including woodpeckers,
Scarlet Tanagers, Brown Thrashers, Meadowlarks, catbirds, kingbirds, and
swallows.
Tiger Sharks also stalk prey, very much the way that terrestrial tigers do,
relying on the element of surprise. Video footage taken via “Crittercams”
attached to Tiger Sharks in western Australia show the sharks approaching
green sea turtles that are feeding on sea grasses. If the turtle looks up as the
shark approaches, the shark veers off. But if the turtle is caught unawares,
the shark attacks. Studies of Bengal tigers in India that attacked fisher-
men in canoes revealed that these predators also attacked from behind.
When fishermen wore Halloween masks on the back of their heads, attacks
declined significantly. Fishermen who were given masks but didn’t wear
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