La plus grande créature qui ait jamais vécu
Ce qu'il faut savoir sur : Baleine bleue
Our Expert Says… "All the statistics about these wonderful creatures are incredible… Their heart is the same size as a compact car; their tail flukes are wider than a soccer goal; their mouth is large enough to hold the equivalent of almost half a million Big Macs at once, but the opening to their throat is only the size of a beach ball… The list of amazing facts can go on and on!"
The blue whale is one of the most iconic whale species. Growing to almost 30m (100ft) long and weighing up to 190 tons, blue whales are the largest creature ever to have existed on earth. And yet these gentle ocean giants feed on tiny, half-inch long crustaceans called krill.
Almost hunted to extinction by commercial whaling in the 20th century, there are now thought to be around 20,000 blue whales in the world’s oceans - 90% fewer than in 1911 at the start of large-scale whaling operations. Hunting of blue whales was banned in 1966, but recovery of the species in areas where they were hit hardest - including the Antarctic - has been slow. Some estimates of Antarctic populations show that although numbers are increasing by around 7% each year, there are still less than 1% of the number of whales in Antarctica compared to pre-whaling populations. Blue whales are officially designated as an Endangered Species.
One of the places in Antarctica with good numbers of reported sightings during the expedition season is around South Georgia Island. For arctic populations, there are regular sightings around Svalbard.
There are 4 sub-species of blue whale, and those seen in Antarctica and the southern oceans are different than those encountered in the arctic and North Atlantic, although they are almost identical in terms of size, coloring, and behaviors.
Because of their deep ocean lifestyle and relatively small numbers, there is very little known about how blue whales interact other than the very strong bond between mothers and calves until they are weaned, common to many whales. Blue whales are generally solitary creatures, although they have sometimes been observed traveling in small groups. We know very little about their mating behavior or where they breed and give birth.
Despite their enormous size, blue whales are known to be predated by orcas, particularly calves. Again, not much is known about the success rates of orcas against blue whales, but there have been several photographic studies that show evidence of scars consistent with orca teeth marks on around 5% of the blue whales that were photographed.
The main threats to blue whales are man-made. Several blue whale deaths from ship strikes are recorded every year, and there are less frequent reports of blue whales becoming entangled in fishing nets or deep-water fishing pots. There are also concerns about marine noise pollution causing behavior change in blue whales among other species.
Climate change is also thought to be a potential disaster for blue whale populations, as rising water temperatures will dramatically reduce the prevalence of the krill stocks on which they feed.