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Breaching, Southern Right whale, Plettenberg Bay

Breaching_Souther_Right_Whale

During the South African winter, Southern Right whales (Eubalaena australis) arrives from the Antarctic to breed and give birth. They normally arrive in Plettenberg Bay in mid-July and stay until mid-September. They were given the name “right” whale, because during the whaling (the massive hunt of whales) they were the right whales to hunt. They are slow swimmers, migrate close to the shore line and float when dead. There is one Northern and one Southern Right whale species. The reason they are classified as two different species is because they don’t cross the equator so they will not breed with each other. In the southern hemisphere there are three different groups, the North Atlantic, North Pacific and Southern Ocean. There seems to be a slight genetic difference between the 3 groups.

Southern right whales grows to 15-17m, 50-65 tonnes and are black with a white patch on the stomach. They don’t have a dorsal fin but large white callosities (barnacles) on the head as identification markers. They have 205-270 baleen plates in the mouth which are about 2m in length.

The migration of the Southern Right whales starts in South Africa where they are born in the shallow bays between June-July. In October they start the long migration to the Antarctic (±5100km). When they reach their feeding ground their mother will spend the summer feeding on 600-1600kg of krill and plankton per day. When autumn arrives they will migrate back to the warmer waters around South Africa. They do this migration every year between their feeding and breeding grounds. The females will return to the same bay to mate and give birth every year. They will have a calf every 3-5 years and migrate at a rate of 2-4 km/hour at a top speed of 15km/hour. They can only keep this speed for a short period of time.

During mating the males will work together to successfully mate with the female. She will mate with more than one male sometimes up to 7. Instead of fighting each other they fight through sperm competition (the one with the largest amount of sperm are most likely to fertilize the egg). Their testacies can grow up to 500kg and 2,5m in length (each) to produce a lot of sperm.
Southern Right whales have a 12 month gestation period and will give birth to 1 calf. They come close in to shore to give birth as the mother (or a midwife) has to get the new born calf to the surface in 10 seconds after the head is out so it can take its first breath. 30 minutes after birth the calf can swim on its own. They weigh around 1 ton and 4-6m in length when born and will suckle for 4-8 months up to 600 litres of milk per day. The milk has a high fat content and the calf will grow 3cm/60kg per day making the calf double in length and increase 5 times in weight. The mother can lose up to 40% in body weight when feeding its calf, but it enables the calf to make the long journey to the feeding ground.

They were a hunted species until the 1935 when the industry collapsed. The estimated amount of Southern Right whales left were 200 individuals with only 60 adult females. Since then the population has recovered with 7% each year and are now estimated to be around 10,000 individuals.

 

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