Fragile Waters: Predator or Prey?
The largest predatory fish in the world – capable of eating marine mammals that weigh several hundred pounds – is the great white shark. The only two fishes that grow larger than Great Whites are the whale shark and the basking shark, both filter feeders that eat plankton. The great white, on the other hand, is known to be an aggressive predator and has an extremely muscular body, capable of chasing down some of the fastest swimmers in the ocean.
Reaching lengths of up to 20 feet (6 m) and weights of several tons, the great white’s body is perfectly adapted to a life of predation.
Great white sharks are known to be highly migratory, with individuals making long migrations every year. In the eastern Pacific Ocean, great whites regularly migrate between Mexico and Hawaii. In other ocean basins, individuals may migrate even longer distances. Like in many highly migratory species, the very largest individuals are female. Great whites mate via internal fertilization and give live birth to a small number of large young (over three feet/one meter). Though they give live birth, great whites do not connect to their young through a placenta. Instead, during the gestation period, the mother provides her young with unfertilized eggs that they actively eat for nourishment. After they are born, young great whites are already natural predators, and they eat coastal fishes. As they grow, their preferred prey also gets larger, and the largest, mature individuals prefer to eat marine mammals, like seals and sea lions. Great whites are known to take very deep dives, probably to feed on slow-moving fishes and squids in the cold waters of the deep sea. Though almost all fishes are cold blooded, great whites have a specialized blood vessel structure – called a countercurrent exchanger – that allows them to maintain a body temperature that is higher than the surrounding water. This adaptation provides them with a major advantage when hunting in cold water by allowing them to move more quickly and intelligently. It is also particularly advantageous when hunting warm-blooded marine mammals that might otherwise have too much energy for great whites to successfully capture them.
While great whites are one of the few species known to have bitten and killed people, these events are extremely rare. Typically, when a great white does bite a person, it only takes one exploratory bite and quickly realizes that the person is not its preferred prey. Unfortunately due to their very large size, even an exploratory bite can be fatal or extremely traumatic. People, on the other hand, capture too many great whites, through targeted fisheries or accidental catch in other fisheries, and scientists generally consider great whites to be vulnerable to extinction. It is known to be a naturally rare species, near the top of the coastal marine food web throughout its range, so accidental or purposeful pressure from humans can be particularly risky. Throughout much of its range, great whites have been given some or complete legal protection, but some catch continues to occur. Noting that there is no “lesser white shark,” scientists refer to the great white simply as the “White Shark.” From Oceana, www.oceana.org
Worldwide in tropical to cold temperate latitudes
Coastal to open ocean (pelagic)
Order Lamniformes (mackerel sharks and relatives), Family Lamnidae (mackerel sharks)
Did You Know?
The Great White Shark’s scientific name means “ragged-toothed”. It comes from the Greek word “carcharos” for ragged, and “odon” for tooth.
Great White Sharks are grey with a white underbelly, from where they get their name. They have a streamlined shape and powerful tails that propel them through the water at over 40 miles per hour!