Ancestry and fossil record

The earliest known fossils are about 16 million years old.

Distribution and habitat

Great White sharks live in almost all coastal and offshore waters which have water temperature between 12 and 24 deg C (54 and 75 deg. One of the densest known populations is found around Dyer Island, South Africa.

It is an epipelagic fish, observed mostly in the presence of rich game like fur seals, sea lions, cetaceans, other sharks, and large bony fish species. In the open ocean it has been recorded at depths as great as 1,220 m (4,000 ft).

A study tracked a great white shark from South Africa swimming to Australia’s north western coast and back, a journey of 20,000 km in under 9 months.

Anatomy and appearance

Great whites display counter shading, having a white underside and a grey dorsal area (sometimes in a brown or blue shade) that gives an overall “mottled” appearance. The coloration makes it difficult for prey to spot the shark because it breaks up the shark’s outline when seen from the side. From above, the darker shade blends with the sea and from below it exposes a minimal silhouette against the sunlight.

Great White Sharks, like many other sharks, have rows of serrated teeth behind the main ones, ready to replace any that break off. When the shark bites it shakes its head side to side, helping the teeth saw off large chunks of flesh.

Size

Males reach maturity at 3.5 – 4.0 metres (11 – 13 ft), and the females at 4.5 – 5.0 metres (13 – 17.1 ft) long and have mass of 680 – 1,100 kilograms (1,500 – 2,400 lb). Females are generally larger than males. It is widely accepted that the great white shark can approach 6.1 m (20 ft) in length and 1,900 kg (4,200 lb) in weight.

Adaptations

Great white sharks, like all other sharks, have an extra sense given by the Ampullae of Lorenzini, which enables them to detect the electromagnetic field emitted by the movement of living animals. Every time a living creature moves it generates an electrical field and great whites are so sensitive they can detect half a billionth of a volt. Even heart beats emit a very faint electrical pulse. If close enough, the shark can detect even that faint electrical pulse.

Ecology and behaviour

The shark’s behaviour and social structure is not well understood. In South Africa, white sharks have a dominance hierarchy depending on size, sex and squatter’s rights: Females dominate males, larger sharks dominate smaller sharks, and residents dominate newcomers. When hunting, great whites tend to separate and resolve conflicts with rituals and displays. White Sharks rarely resort to combat although some individuals have been found with bite marks that match those of other white sharks. This suggests that when another shark approaches too closely, great whites react with a warning bite. Another possibility is that white sharks bite to show dominance.

The white sharks are generally very curious animals, display intelligence and may also turn to socializing if situation demands such.

Diet

Great white sharks are carnivorous, and prey upon fish (eg tuna, rays, other sharks), cetaceans (ie dolphins, porpoises, whales), pinnipeds (eg seals, fur seals, and sea lions), sea turtles, sea otters, and seabirds. Great whites have also been known to eat objects that they are unable to digest. These sharks prefer prey with a high content of energy-rich fat.

Hunting techniques vary by prey species. Off Seal Island the shark ambush cape fur seals from below at high speeds, hitting the seal mid-body. They go so fast that they can completely leave the water. The peak burst speed of these sharks is largely accepted in the scientific community to be above 40 kilometres per hour (25mph). However further precision is still speculative. They have also been observed chasing prey after a missed attack. Prey is usually attacked at the surface.

White sharks also scavenge on whale carcasses. In one such documented incident, white sharks were observed scavenging on a whale carcass alongside tiger sharks.

Reproduction

Little is known about great white shark behaviour in the way of mating habits. Birth has never been observed, but pregnant females have been examined. Great white sharks are ovoviviparous (eggs develop and hatch in the uterus, and continue to develop until birth). The great white has an 11 month gestation period. The shark pup’s powerful jaws begin to develop in the first month. Stronger pups consume their weaker womb-mates. Delivery is in spring and summer.

Great white sharks reach sexual maturity at around 15 years of age. Maximum life span is believed to be more that 30 years.

Breaching behaviour

A breach is the result of a high speed approach to the surface with the resulting momentum taking the shark partially or completely clear of the water. This is a hunting technique employed by great white sharks whilst hunting seals. The shark can reach speeds of up to 40 miles per hour and can at times launch themselves more than 10 feet in the air. Data recorded shows that the sharks are successful in just under 50% of all these natural predatory events.

Relationship with humans

Shark attacks

Great white sharks do not typically target humans: for example, in the Mediterranean Sea there have been 31 confirmed attacks against humans in the last two centuries, most non-fatal. Many incidents seem to be “test-bites”. Great white sharks also test bite buoys, flotsam, and other unfamiliar objects, and might grab a human or a surfboard to identify it.

Other incidents seem to be cases of mistaken identity, in which a shark ambushes a bather or surfer from below, believing the silhouette is from a seal. Many attacks occur in water with low visibility, or other situations which impair the shark’s senses. The species appears to not like the taste of humans, or at least finds the taste unfamiliar. Further research shows that they can tell in one bite whether or not the object is worth attacking.

Humans, in any case, are not appropriate prey because shark’s digestion is too slow to cope with the human’s high ratio of bone to muscle and fat. Accordingly, in most recorded attacks, great whites broke off contact after the first bite. Fatalities are usually caused by blood loss from the initial limb injury rather than from critical organ loss or from whole consumption.