Humpback Whales Migration

It is that favourite season for the whale watchers again. The Humpback whales back at the Kenyan Coast to mate and give birth.

 

The humpback whale gets its common name from the distinctive hump on its back.  Its long pectoral fins inspired its scientific name, Megaptera novaeangliae. Megaptera, means “big-winged” and novaeangliae, which means ‘New England’ in reference to the location where European whalers first encountered them.

The humpback whales have one of the longest migrations of any on the planet. They swim over 5,000 kilometers annually from colder polar feeding waters (high latitude grounds) to the warmer mating and calving waters (low latitude grounds).

Humpbacks are massive. They range from 12 to 16 meters (39 to 52 feet) in length and weigh approximately 40 tonnes. They are mainly black or grey with white undersides to their flukes, flippers and bellies. 

Despite their massive size, the humpback whales feed on krill (small shrimp-like crustaceans), plankton, and small fish. They catch them by straining huge volumes of ocean water through their baleen plates, which act like a sieve.

They use a unique method of feeding called bubblenetting. They dive deep then swim up in a spiral pattern, while releasing a steady stream of bubbles from their blow holes. As the bubbles rise they form a "net" that surrounds the whales' prey. The whales swim up through the centre of the bubble net and feed on the prey trapped inside.

The humpbacks are one of the most acrobatic cetaceans. They frequently breach by leaping belly-up completely clear of the water, then arching backward and returning to the surface with a loud slapping sound. When beginning a deep dive, they hunch their back and rolls steeply forward, bringing its tail out of the water and perpendicular to the ocean surface.

Humpbacks are famous for their "songs." Male humpbacks produce a long series of calls that are normally heard during the winter breeding season. The whales may repeat the same song for several hours.  The songs appear to be shared by all singing members in the same area of the ocean: as the song changes, all members sing the new song. The same song is sung in spite of the great distance between groups in the population (up to 5000 km). This sharing of songs may occur when groups intermingle during migration or in shared summer feeding grounds.

The humpbacks have complicated courtship behaviours. Often, many males will surround a single female hitting each other in a competition to get close to her. Females become pregnant about every two to four years, and are pregnant with each calf for about 11 to 12 months. The calves can grow 0.5 metres every month while nursing on their mother’s rich milk. Females nurse their newborn calves in warm, shallow water. 

After spending two months breeding and nursing their calves, the whales will then make their journey back to Antarctica around September.