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White shark populations may separate according to size, gender and for reproduction. However, the ratio of males to females changes depending on location, season and over time. Juveniles are most commonly encountered in inshore areas, often in the vicinity of open coast beaches. The Great Australian Bight, Victor Harbour to Coorong region ( South Australia), areas off Portland and Ninety Mile Beach ( Victoria), Garie beach to Wattamolla and Port Stephens to Newcastle ( New South Wales) and some areas off southern Queensland appear to be seasonally important for juvenile white sharks. The areas where juveniles are mostly found may represent white shark pupping grounds.
What do they eat?
White sharks have few natural predators and do not feed continuously. A large meal (e.g. a seal) may last a medium size shark for as long as a week. They appear to eat different foods as they get larger, with smaller ones (less than 2.7 metres) feeding on a variety of fish, cephalopods and crustaceans. As they increase in size, their diet expands to include marine mammals. They are also scavengers and will feed on the bodies of large dead cetaceans when available. Larger white sharks (greater than 3 metres in length) are frequently found near seal or sea lion colonies in Australia.
How do they reproduce?
There is little information on the reproductive cycle of white sharks because examination of mature adult specimens (in particular females) is rare. Adults are large, fairly uncommon and when captured, their size makes preservation and examination difficult. However, it has been established that white sharks display oophagy.
White shark pups are 120–150 cm long and up to 32 kg at birth and litter sizes vary from 2–10. It is not known how long it takes for an embryo to mature, but it may take about 18 months, with females breeding only once every 2–3 years. It is suggested that the birth period occurs between December and June. Nursery areas (pupping grounds) are located in inshore coastal waters.
How big do they grow?
In general white sharks will reach a length of 2 metres in about 3 years; 3 metres in 5–8 years; and 5 metres in 16–23 years. Male white sharks mature at about 3.6m, when they are thought to be at least 10 years old. Females mature at about 4.5 – 5 metres when they are thought to be around 18 years old. The lifespan of these sharks is thought to be more than 30 years.
What kind of environment are they found in?
The white shark is mainly found in continental shelf waters, often occurring close inshore near the surf zone. They can swim long distances. They have been recorded moving about 190 km in 2.5 days at an average speed of 3.2 km/hr, and satellite tracking has confirmed migrations of almost 6000 km in 200 days. However, there have been several reports of individual white sharks revisiting the same place year after year. Sharks in southern Australia have shown a wide range of swimming behaviours including:
- Regular dives and ascents between the surface and the bottom;
- Swimming deep at night and in shallow water during the day; and
- Spending long periods at the surface or at the bottom.
Movements are mainly restricted to shelf and coastal waters in depths down to 100 metres.
Next - Do they migrate?
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