Marine Species in Port Elizabeth, Algoa Bay
Humpback Whale (Megaptera novaeanglia)
The name humpback was derived from the way they arch their backs prior to a deep dive. This whale was ruthlessly hunted in the past which led to a population decrease of 90%. They were considered endangered by 1966, but have steadily recovered, reaching a worldwide population of at least 60,000. However, they still face threats from entanglement in fishing gear, collisions with ships and noise pollution, not to mention the sabre rattling of the Japanese whaling fleet.
Humpback whales can be 11-18 metres in length and 24-40 tons in weight. The heaviest humpback to date was washed ashore at Mouille Point in Cape Town, in 1995. It had obvious cuts from a ship’s propeller and was found to weigh 59.4 tonnes. They are easy to spot as they have a very small dorsal fin, long flippers which are 30% of their total body length, white patches on the underside of their belly, flippers and tail fluke, a three metre vertical high blow, and small knobbly protrusions on their head called tubercles. Tubercles are hair follicles which actually have a single, 2.5cm long hair extending from each. These organs are thought to assist with prey location and capture. Humpback whales dive typically for 3-15 minutes but have been known to stay submerged for up to 40 minutes. They can reach depths of up to 150 metres. They can be found in groups of up to 15, but more often singly or in cow/calf or calf/sub-adult pairs.
Unlike Southern right whales, humpbacks have throat grooves (like other rorqual whales) which distend when feeding. This makes a much bigger cavity available to take in more water and food at a time. Humpback whales feed on krill and small fish and often work cooperatively when feeding. In the Northern hemisphere humpback whales will circle a school of fish while blowing bubbles, which creates a screen around the school, so they can’t escape. This method of ‘bubble-net feeding’, along with vocalisations, gives the whales time to then swim upwards through the net, mouths agape, swallowing thousands of fish in one gulp. This method of swimming upwards with mouth open wide is known as ‘lunge-feeding’ and is employed by most rorqual whales. Humpback whales feed during the summer months around the waters of Antarctica and live off their fat reserves in winter. They may however feed opportunistically at their breeding grounds.
Humpback whales have one of the longest migrations of any mammal as some will swim 16,000km to and from their breeding grounds (click here for map). They have a gestation period of about 11.5 months, after which calves will suckle for about 6 months to a year, staying with the mother for 1-2 years. Females give birth every 2-3 years and new-born calves are about 4 metres long and weigh a ton. Males are famous for their complex courtship songs, each lasting 10-20 minutes which may be repeated for several hours.
Read here for more information on our whale watching cruises in South Africa.