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social behaviour of white sharks & reproduction
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information

Social Behaviour Of Great White Sharks

Great whites are usually solitary animals but are occasionally seen in pairs. Scientists are beginning to understand more about the behavioural interactions between great whites.

Sharks definitely interact with each other and communicate using body language. For instance stiff, arched bodies and gaping mouths (underwater) seem to be threat displays warning off other sharks. Some of the white's swimming habits, such as a carefully timed turn away between two sharks on approaching courses, is interpreted as maintenance of individual space. Parallel swimming with two sharks heading in the same direction at an equal distance from each other, also seems to a means for the shark to preserve its space from others.

When white sharks feed on the same prey, it doesn't make sense for one to bite and wound the other as this may reduce either shark's future ability to catch prey. For this reason white sharks use displays in order to discourage other sharks. White sharks have been observed with their caudal fin out of the water slapping the surface, usually in the direction of a second shark. This "tail slap" is the most common avoidance display shown by white sharks.

Sometimes a white shark will position itself between prey and another shark, preventing the second shark from feeding. White sharks have also been known to propel their body out of the water and land flat against the surface, causing a large splash. This behaviour is called a breach and may represent a similar message to the tail slap. Breaching might also help remove external parasites, attract a mate or may be the result of a vertical charge approach toward its prey.

Reproduction

White sharks are viviparous. Fertilisation of the eggs occurs in the female, and later the eggs actually hatch inside her, and she gives birth to live young. Embryos are nourished through ingestion of unfertilised eggs, as there is no placenta. Size at birth ranges from 120-150cm (47-59 in) in length. The newborn shark is not cared for by the mother, and swims away from her immediately after birth.

Scientists believe that females become reproductive after about 10 years and are likely to produce litters of 6 to 10 pups. Gestation time is unknown, but is thought to be quite long, possibly up to one year. Scientists don't know how many litters a female produces in her lifetime and aren't sure how long after the last litter a female becomes receptive again. As in other species of sharks, the male white shark most likely bites the female during mating.

Predators

The white shark is an apex predator (on top of the food chain) and as such, has very few predators. Killer whales and larger sharks pose the only natural threat to an adult white shark.

Despite being rare, the white shark's rate of capture by humans is alarmingly high. This is due partly to the increasing value of its jaws and teeth. Their fins are also used for shark fin soup. In the despicable practice of finning the fins are sliced off of the shark and then the living animal is left to die. Also, the flesh is eaten, the skin used for leather, the liver for oil and the carcass for fishmeal. In South Africa another problem for the white sharks is shark nets. In KwaZulu-Natal up to 40 white sharks are killed annually in the nets alone.


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