The largest animal in the world was once brought shockingly close to extinction by relentless whaling. There used to be over 250,000 blue whales in our oceans, but hunting reduced blue whale numbers to just a few hundred. Although the hunting of blue whales is now banned by the International Whaling Commission, there are still very few blue whales compared to the days before whaling. Continue to read on or download the fact sheet to learn more blue whale facts.
What do they look like?
Blue whales are named for the beautiful aquamarine colour they appear when underwater, but when at the surface the skin actually looks a mottled blue-grey. This mottling pattern is different on each blue whale and so can be used to identify individuals.
When a blue whale is at the ocean’s surface, you may be able to spot the small fin on its smooth back, near the tail, and see a tall column of water vapour, reaching up to 12 metres high, as the whale exhales.
Two ‘types’ (subspecies) of blue whales are found around Australia: the Antarctic blue whale and pygmy blue whale. Antarctic blue whales grow up to 30 metres, while pygmy blue whales are smaller but despite their name still grow to 24 metres in length.
What’s their lifecycle?
Antarctic blue whales are extremely long-lived animals, living up to an incredible 90 years, while pygmy blue whales live to around 50 years. Adult female blue whales usually give birth to an infant every two to three years, after a pregnancy of approximately 11 months. Females nurse their young for around 7 months.
Considering their immense size, blue whales feed on surprisingly small prey – tiny shrimp-like creatures called krill. They therefore have to eat an incredible amount of krill, up to 8 tonnes each day, to sustain themselves. They may either feed at or near the surface, lunging at a school of krill with their mouths open, or dive down to incredible depths for their meal. Blue whales can dive down to 500 metres where they can remain for around 50 minutes before having to return to the surface for air.
What threats do they face?
Key feeding areas are vital for blue whales, and so anything that poses a risk to these critical areas poses a threat to blue whales. In recent years, ocean noise pollution around key feeding areas in Australia has increased. This noise, which comes from ships and seismic testing by oil and gas companies, could result in deterring blue whales from their important feeding areas.
Blue whales are also at risk from collisions with boats, known as ‘ship strikes’, which can be fatal. This is a particular threat where busy shipping lanes overlap with key areas of habitat.
Like many animals, climate change may also threaten the future of blue whales. Climate change is predicted to change ocean currents and temperature, which could alter blue whale habitats and affect the availability and distribution of their food. In light of such change, human activities, such as krill fisheries, could put additional pressure on this endangered mammal.
Where can I see them?
Around Australia, there are a number of important areas offshore where blue whales feed: the Perth Canyon, Kangaroo Island and the Bonney Upwelling off South Australia and Victoria. The place you’re most likely to see blue whales from shore is Geographe Bay, Western Australia, as they pass through between October and December.
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