142 Sharks: The Animal Answer Guide
chemicals form the basis of many questionably successful shark repellants
that sharks detect via either smell or taste (see “How can sharks be re-
pelled?” in chapter 9).
How do sharks catch their prey?
Because different sharks eat so many different things, the means by
which they catch and consume prey vary among and even within species,
depending on circumstances. At the most basic level (aside from just biting
down on something), sharks can be divided into those that chase after live
prey, those that ambush prey, those that inhale prey via suction, and those
that filter prey with an open mouth while swimming.
Chasers. Most sharks probably chase after prey at some time in their
lives, if only for a short distance. But those best known for making a liv-
ing this way are makos, Porbeagle, Salmon, Sand Tiger, Sevengills, and
many carcharhinid sharks. Makos are the classic pursuit predator, not sur-
prising because they are also the fastest shark and consequently the most
sought-after shark as a game fish (see “What is the fastest shark?” in chap-
ter 1). Many of the sharks that “specialize” in chasing, but especially the
makos, Salmon Shark, and Sand Tiger, have long, spiky teeth best adapted
for grasping slippery fishy prey on the run.
A special group of chasers make the initial attack using something other
than their teeth. Ecologically, these are some of the most interesting feed-
ers, with a diversity of attack methods unrivaled by bony fishes. The de-
vices these sharks use include biological hammers, swords, scythes, and
shockers.
We’ve seen that there are a number of hypotheses about how hammer-
head sharks use their “expanded cephalic foil,” but one use has been veri-
fied by observation. Hammerheads use their flattened head to knock sting-
rays down to the bottom and then use the same flattened head to pin a ray
down while taking bites from its wings.
The Great Hammerhead feeds extensively on stingrays. Snorkeling in
6 m (20 ft) of water over a seagrass bed, researchers in the Bahamas saw a
3-m-long (10-ft) Great Hammerhead chasing a 93-cm-wide (3-ft) Southern
Stingray. The shark thrust its head down against the back of the ray, knock-
ing it to the bottom. The shark then pinned the ray against the bottom
with its head and pivoted around on the back of the ray, taking a bite from
the front edge of the ray’s left pectoral “wing.” The ray limped off, and the
shark pinned it to the bottom again, pivoted, and took a bite from the front
of the right pectoral fin. This crippled the ray, which was then eaten by the
shark. The shark used its hammer to both knock the ray down and then
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