The Humpback Whales sightings the past week have been amazing at Ocean Blue Adventures, with guests having a blast.
Did you know:
Humpback Whales (Megaptera novaeangliae) can grow up to 15m in length and weigh between 30-40 tonnes making it the 5th largest whale. They are normally found migrating single or in small groups aggregating in their feeding and breeding grounds. Humpback whales can live to 60 years or older. They are grey/black on their dorsal and white on the stomach. The white marking on the underside of their tail can (together with the dorsal fin) be used for photo-identification of different individuals. They have grooves on their throat running from the mouth to the naval. These grooves make the throat work just like the pouch of a pelican (extendable) to accommodate for large amount of food. Humpback Whales have large flippers (1/3 of their body length). It´s from their flipper they got the genus name Megaptera which means “huge-wings”. The flippers have nodules on the leading edge of the flippers that increase aerodynamic efficiency due to decrease in tubercles. This means that the nodules helps the Humpback Whale swim easier and “fly” under water. This technique is used in turbine to improve the blades movement and has increased their efficiency with 40%.
Humpback Whales in the southern hemisphere are born in the tropical waters around Australia, South Africa and South America in winter (July-August) and will migrate down to the Antarctic in the summer to feed. Humpback Whales visiting the South African coastline split into two groups around Agulhas, migrating to Mozambique or Angola. In Plettenberg Bay we can see them twice a year, on their migration to their breeding ground (July-August) and on the migration to their feeding ground (October-November). Humpback Whales are social animals that form small social groups that they will spend a lot of time with at their feeding and breeding grounds. Humpback Whales migrate with about 12 km/h with a max speed of 25 km/h.
Female Humpback Whale reaches sexual maturity at 5 years of age and the males around 6 years of age. Females give birth to a 2 ton, 4m long calf after an 11 month gestation period every 2-3 years. It’s been seen on rare occasion that females have calves on consecutive years. This is only possible when the females have access to a good food source since having one suckling calf while pregnant is hard on the body. Humpback Whales are seen as gentle animals, but during breeding season the males become very aggressive when claiming females. Sometimes up to 20 males try to dominate one female. It is at their breeding grounds that they are commonly associated with their “singing” to attract the females. This song can last 35 minutes up to days in length only pausing to take a breath. This song can be heard for up to 160 km. The song from different parts of the world is different and each male has its own unique song. Males have been seen pushing away calves from their mothers trying to mate with her and have most likely killed calves to get to the females.
When Humpback Whales are in there feeding grounds they feed mostly on plankton, squid and fish that congregate in large schools in the Antarctic waters. Humpback Whales are famous for their bubble-net feeding. They will work together by blowing bubbles into a cylinder shape and the fish driven into the cylinder from below will not cross the “bubble barrier”. The whales then take turns to take big “bites” from the cylinder swallowing the fish. The southern hemisphere Humpback Whales mainly feed on krill while the northern hemisphere primarily eats fish.
During whaling of Humpback Whales they were taken on their migration route as well as in their feeding and breeding grounds. They were hunted because they are easily found and curious about boats. They are often seen breaching, flipper or tail slapping making it possible to locate them at a distance. Humpback Whales became a prime target during the modern era of whaling (1863-present) and between 1900 to 1940 over 100,000 Humpback Whales were taken in the southern hemisphere. In 1963 Humpback Whales received full protection from commercial whaling, but are still threatened by pollution and getting entangled in fishing nets. Since the protection in 1963 surveys along the South African coastline suggest an increase of Humpback Whales with approximately 10% each year. The total population size in the southern hemisphere is around 60,000 animals and the estimated population size from before the whaling was 75,000-100,000 individuals. Humpback whales are classified as least concerned on the red list but as all marine mammals they are protected in South African waters.