Humpbacks whales are common sight off the WA coast in October and November. We often see them when walking the Cape to Cape in spring.
The whales mate and calve in tropical waters in winter and then travel to cold polar waters during the summer to feed. In WA, whales mate and calve up in Camden Sound off the Kimberley coast.
During the summer in the warm waters, and on their way back south, adults don’t eat, but live off their layer of blubber. The calves feed on their mother’s milk – about 200 litres a day! And it’s not runny watery stuff; it’s thick, like toothpaste, and nutrient dense.
Humpback whales migrate at 5-14 km/h. They can dive for up to 40 minutes, but usually last only up to 5-15 minutes. They can dive down 150 to 200 metres.
The most exciting time to see them is when they breach. Breaching is likely to be largely for communication, as the sound of a breaching whale travels a long way underwater, but might be just playing or might be used to loosen skin parasites. They’ve got two blowholes (one for each lung) so their spurts are very distinctive, coming out as two jets of water.
Song lines of Humpback Whales
A whales song is learned, not innate, and they can be popular or unpopular, like a pop song. A few years ago, researchers learnt about a Western Australian whale that went over to the east coast. Such was the sandgropers tune, that he became very popular with the lady whales. Consequently many of the east coast male whales copied the Western Australian songs. In the coming years the east coast songs died out and the WA songs had taken over – top of the charts!
Humpback whales are baleen whales (no teeth). Their mouth is a third of their body with a tongue as big as a car. They’re seasonal feeders and work together in a highly coordinated way to feed on crustaceans and small fish like herring.
First there are the herder whales who circle around and around a school of fish, waving their fins. Then the caller dives below the shoal and emits a defining cry – 180 decibels of noise that panics the fish and makes them swim upwards. Then the ring leader takes up a position just above the shoal and releases air bubbles in a wide circle to create a net of bubbles which the fish swim up into. The shoal is prevented from dispersing by the herders and the bubbles, which they won’t swim through. The whales take up position below the shoal and, at the leaders call, they all swim up with their mouths open to get a mouth-full of fish. The whales always come up in the same pattern.
An average-sized humpback whale (12 – 15 metres long) will eat 1000 to 1500 kg of plankton, krill and small, schooling fish each day during the feeding season in cold waters (about 120 days).
Humpback whales have over a metre of ear wax! That’s how researchers used to tell how old they were – by taking a core sample of ear wax and counting the rings! Scientists can also analyse the chemical composition of ear wax columns and find out about a whales life events: like if and when a whale was exposed to pollutants like mercury, and when the whale went through puberty (because of the change in hormone levels).
In recent years the number of humpback whales off the coast of have increased so now it is quite easy to spot them during spring. They are an amazing animal and it is always exciting to watch them breach when we are walking.