Humpback Whales

Humpback whales are very active at the water surface and often approach boats. They are easy to recognize at sea since they produce a well visible, bushy blow and raise their fluke above the water surface before almost every dive.

Humpback whales got their name because of a little hump slightly before the dorsal fin. The dorsal fin itself is small and highly variable in shape. On the head of humpback whales are lots of lumps which are called tubercles. In the centre of each tubercle grows one 1-3cm long hair. Only very few whale species possess hair when they are adult. Humpback whales are usually 14-15m long whereby females are 1-1.5m longer than males. Calves are born with a length of 4-4.5m after a gestation period of 11 months.

The calves start feeding independently after about six months although they are suckled up to one year. Humpback whales usually give birth to one calf every second year.

For mating and calving these whales swim towards tropical and subtropical latitudes to reach their so called breeding grounds. After breeding season, which is in winter, the humpback whales swim to the highly productive polar waters which contain plenty food. There they feed during summer. Some humpback whales move up to 9000km between their breeding and feeding grounds. These migrations are along the longest known for mammals.

What is that? Krill is a certain shrimps species which is basic food for many big whale species. There is one known non migrating humpback whale population inhabiting the waters of the Arabian Sea.

How can that be? The monsoon mixes the water quite well whereby nutritions which were sunk to the sea floor come up to the surface. Since there are nutritions algae can grow, animals which feed on algae like small shrimps and fishes appear and thus there is food for the humpback whales. So the whales stay in these tropical waters year round. This is one example showing that the movement of whales strongly depends on food availability.

Humpback whales developed many ways to feed. The most exciting one is the bubblenet feeding. This is were one whale or several animals swim in a circle while blowing bubbles out of their blow holes. Thereby building a cylinder shaped net consisting of bubbles. Then the whales dive under the herring school and drive the fishes towards the water surface into the bubble net. Since fishes do not cross these bubble curtains, they can't escape. The whales approach them from underneath and swim through the school with their mouths wide open.

This requires complex social coordination. Communication during feeding usually takes place acoustically. Whales produce different sounds for different purposes. During breeding season male humpback whales even sing complex songs which usually last 10 to 15 minutes. These songs are repeated again and again often for many hours. These songs change during the season and differ between geographic regions. Their primary function is probably to attract females. Since all males in one area sing the same song, it is probably the volume which makes the difference for the females. The louder the male sings the more attractive it is. Often there are several male humpback whales around one female which fight aggressively for access to the cow. The males hit each other with their flukes, they slap the water surface with their flippers and tails and release streams of bubbles from their blow holes.

Sometimes one male follows one female for several hours or days in the hope that she comes into estrus and is therefore willing to mate. This is called a cow-escort group.

Humpback whales are cosmopolitans which means they occur in all of the world's oceans.

Whale Species