Life History Sketch of Great White Sharks at Seal Island

Great White Shark Breeding – As individuals less than 2 metres in length are conspicuously absent, White Sharks do not appear to breed at Seal Island nor anywhere within False Bay. In southern Africa, this species is believed to give birth during late spring or early summer in Eastern Cape waters, but details on precise pupping grounds are sketchy.

In South African waters, male Great White Sharks become sexually mature at a length of 3.5 to 3.6 metres and an age of 9 or 10 years, females mature at a length of 4.5 to 5 metres and an age of 14 to 16 years. The females grow larger than the males, reaching a maximum length of at least 7 metres and a mass in excess of 2,000 kilograms, although individuals over 6 metres in length are extremely rare.

Gestation period in the Great White Shark is not known, but may be longer than one year, with mature females breeding only every third year. White Shark pups measure between 1 and 1.5 metres in length and about 60 kilograms at birth. Litter size in this species ranges from 5 to at least 10 and possibly to 14 pups.

Great White Shark Foraging – Diet of the White Shark at Seal Island has received little quantitative investigation. A 3.9-metre male specimen that washed ashore in False Bay near Simon’s Town in [month?] 1998 was examined and found to contain remains of Cape Fur Seals only. The relatively fresh carcass of an 11-metre Bryde’s Whale that washed ashore at Glencairn Beach, about 3.5 kilometres north of Simon’s Town, on 5 July 2000 was towed to Seal Island the following morning and promptly attracted the scavenging attentions of at least 28 individual White Sharks.

Great White Shark Movements – White Sharks appear to arrive at Seal Island at early-to-mid-April each year, remaining in the immediate area until at least September. During this time, they feed heavily on Cape Fur Seals, with peak predations occurring during June, July and August. In 1999, perhaps as a consequence of the unusually mild winter, White Sharks were in evidence at Seal Island until the end of October. From December through January, White Sharks are conspicuously absent from the waters surrounding Seal Island and are most often sighted closer to shore, in Muizenberg beach , Fish Hoek and off Macassar Beach.

Although they often aggregate when and where prey is seasonally abundant, Great White Sharks are highly nomadic. Individuals tagged at Seal Island have been re-sighted at Dyer Island and Mossel Bay, distances of about 175 and 350 kilometres, respectively. A nearly 5-metre female individual tagged at Struisbaai was recaptured off Natal, having travelled 720 kilometres in 27 days.