Shark and Their Relatives

Behavior

A. Daily activity cycle

Recordings of the movements of tagged sharks suggest that most sharks undergo daily activity rhythms. Their greatest activity occurs during the twilight and dark hours.

B. Social behavior

Although sharks and batoids are basically asocial, many species demonstrate various degrees of social behavior. For instance, hammerhead sharks commonly school.

C. Symbiotic relationships

1. Pilotfish (usually Naucrates ductor, but there are others) often travel with sharks, for unclear reasons. This relationship may be due to the natural schooling behavior of pilottish, or the pilotfish may conserve energy by riding the hydrodynamic bow wake of the shark. Pilotfish also eat small amounts of food scraps released as the shark feeds.

2. Several species of small fishes, notably the cleaner wrasse (Labroides dimidiatus), are "cleaners" that pick debris and parasites from sharks.

3. Remora (several species in the family Echeneidae) commonly attach themselves to sharks and batoids or ride their hydrodynamic bow wakes. In addition, they may eat parasites of sharks and batoids.

4. Parasites of sharks and batoids are mainly copepods (small crustaceans) and flatworms.

D. Shark attack

1 . Only 32 species of sharks have been identified with attacks on humans or boats. These species have three features in common: they prey on fish or marine mammals, grow to a large size, and frequent warmer coastal waters where swimmers are apt to be.

2. In 1958, the U.S. Office of Naval Research and the American Institute of Biological Sciences set up the Shark Research Panel-a union of scientists that gathered documentation on shark attacks and compiled the information into the Shark Attack File. The Shark Research Panel documented the following:

a. Humans become prey by accident. Most shark attacks involve people handling hooked or snared sharks or spearfishermen handling wounded fish. Through sight or sound, a shark may confuse swimmers or divers for prey.

b. Sharks may also attack from a territorial drive, with no intention to feed. A characteristic swimming pattern called agonistic display usually precedes attacks out of territoriality. The shark shakes its head and swims erratically with a hunched back, pectoral fins pointing down, and snout pointing up.

A characteristic swimming pattern called agonistic display usually precedes attacks out of territoriality.

3. An analysis of 1,000 recent shark attacks world-wide showed that well over 50% of the attacks were not feeding-related.

4. Up to 60% of shark attack injuries are slashes of the upper jaw teeth. This behavior is typical of courtship advances by some male sharks.

5. Sharks may also injure victims by bumping them vigorously, but most sharks move in cautiously when attacking.

6. A great white shark (Carcharodon carcharias) rushes towards its prey, attacking from beneath and behind. These sharks rely on stealth and surprise to prey on seals, sea lions, and other marine mammals.

a. After a great white shark bites its victim, it swims a short distance away, waiting for its victim to bleed to death. If rescuers are nearby, many human victims survive the attack.

b. Great white shark populations may be increasing along the coasts of California and Oregon due to increasing populations of seals and sea lions. Marine mammal populations are increasing as a result of federal protection. Populations of predators naturally increase as food becomes more readily available.

c. To reduce the chance of an attack by a great white shark, swimmers and divers should stay clear of seal and sea lion rookeries, or other known areas frequented by the sharks.

d. Swimmers and skindivers at the surface are more prone to attack than SCUBA divers beneath the water. At the surface, a swimmer's or diver's silhouette resembles that of a seal. Great white sharks may not be able to make the distinction.

e. California has one of the highest great white shark attack rates in the world. Yet fatalities average only one every eight years.

7. There is no known effective shark deterrent.

SeaWorld/Busch Gardens Animal Information Database
www.seaworld.org/www.buschgardens.org