The great white shark
averages 4.5 m (15 ft.) in length, but some have been recorded as large as 6 m
(20 ft.) long! They generally weigh up to 2250 kg (5000 lb.).
Great white sharks are
blue-gray on the dorsal, or top, part of their bodies. This helps them blend in
with the bottom of the ocean when viewed from above. The belly, or ventral,
part of the body, is white. This makes it difficult to see the sharks from below,
with sunlight shining in around them. They have strong, torpedo-shaped bodies
and powerful tails that help them swim. Great whites can reach speeds up to 24
km/hr (15 mph).
Great whites use their
speed and coloring to help them hunt. They search for prey at the surface of
the ocean while swimming below. Once they spot a target, they use a burst of
speed to bump their prey while simultaneously biting it. They have several rows
of teeth that can number into the thousands. As teeth fall out, they are rapidly
replaced by those in the row behind them. These sharp, serrated teeth can be
devastating. A single, large bite can be fatal.
When great white sharks
are young, they feed on smaller prey, like fish and rays. As they grow larger,
they feed more exclusively on marine mammals, such as sea lions, seals and
small whales.
The great white is at the
top of the food chain and has few threats in the ocean. Only orcas and larger
sharks can pose a risk. The only other risk to the great white shark is human
interaction. They are sometimes caught by accident in fishing nets or
intentionally sought out by sport fisherman. Their jaws and fins are sold for
considerable amounts of money.
Not much is known about
the mating habits of great white sharks. What is known is that after mating the
female develops several eggs which hatch in her womb. The newly-hatched shark
pups feed on unfertilized eggs in the womb as they develop before being born.
In general, the mother gives birth to a litter of two to ten pups, each of
which average 1.5 m (5 ft.) in length. Male great whites reach maturity at 9-10
years of age. Females mature even later, between 14 and 16 years of age. Female
sharks are thought to give birth once every couple years, but even that is
uncertain.
Many paleontologists are
very interested in living groups, because the study of the living organisms can
both unlock their evolutionary history and provide important keys towards
interpreting their fossil record. Some living groups have ancient histories.
For example, sharks have existed as a group for over 350 million years! Today,
sharks and rays (elasmobranchs) are represented by over 600 species that show a
remarkable range of ecological and morphological diversity. Unlike the true
fishes, sharks do not have internal bone, but instead have a cartilaginous
skeleton. Although many people are told that sharks are primitive in comparison
to other groups, this is not true. Many sharks are efficient and specialized
hunters that have thrived for millions of years.
This small exhibit shows
an amazing predator: the great white shark (Carcharodon
carcharias). The white shark is found in temperate waters throughout the
world's oceans, and it is an important, though not common, predator in
California's coastal habitats. Scientists from several organizations throughout
California including the Point Reyes Bird Observatory, the Marine Mammal
Center, the California
Academy of Sciences, Bodega Bay Marine Laboratory, California
Department of Fish and Game, and the Museum of Vertebrate Zoology at UC
Berkeley, have been studying white sharks and their prey for several years in
hopes to better understand their behavior and ecology.
White
sharks are predatory animals that begin life by feeding on fish, rays, and
other sharks, and as they grow, switch to feeding on marine mammals and
scavenging on large animal carcasses. Their first mammalian prey are usually
the small harbor seal, but as the sharks increase in size, they become large
enough to eat sea lions, elephant seals, and small toothed whales. Attack
strategy consists of a swift, surprise attack from below, inflicting a large,
potentially fatal bite. The pinniped often dies from massive trauma or blood
loss, but the bites may be superficial or misplaced on the body, allowing the
seal to escape and survive the attacks with their scars as witness. Large white
sharks will also scavenge on the carcasses of whale sharks, and on the fat-rich
blubber layer of dead whales. They will occasionally feed on sea turtles and
sea otters, and are known to attack, but not eat, humans.
The
great white shark came into existence during the mid-Miocene epoch.
The earliest known
fossils of the great white shark are about 16 million years old. However,
the phylogeny of the great
white is still in dispute. The original hypothesis for the great white's
origins is that it shares a common ancestor with a prehistoric shark, such as the C. megalodon. Similarities among the physical remains and the extreme size of both
the great white andC. megalodon led many scientists to
believe these sharks were closely related, and the name Carcharodon megalodon was applied to
the latter. However, a new hypothesis proposes that the C. megalodon and the great white
are distant relatives (albeit sharing the family Lamnidae). The great white is also more closely related to an ancient mako shark, Isurus hastalis, than to the C. megalodon, a theory that seems to be supported with the
discovery of a complete set of jaws with 222 teeth and 45 vertebrae of the
extinct transitional species Carcharodon hubbelli in 1988 and published
on 14 November 2012.[ In addition, the new hypothesis
assigns C. megalodon to the genus Carcharocles,
which also comprises the other megatoothed sharks; Otodus obliquus is
the ancient representative of the extinct Carcharocles lineage.
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