This enormous whale was hunted to the brink of extinction, and there are still fears for its future.
Balaenoptera musculus is the biggest animal alive, and thought to be the largest that has ever lived. The huge body size is only possible because of the support given by water – on land the enormous weight would simply crush the whale, so stranded Blue Whales always die.
Size
It is difficult to weigh such a large animal accurately, but estimates suggest that 200 tons (American ‘short ton’) is reasonable for a 30m whale. The largest dinosaurs were only half that weight, although some were a bit longer (Amphicoelias fragillimus was probably over 40 metres, but most of that was a long skinny neck and a thin tail). The heart of an adult Blue Whale can weigh over 600kg, and a new-born calf is as big as a hippopotamus!
Blue Whale Food
It is paradoxical that such a large animal eats such small food. Blue Whales feed almost exclusively on Krill which are the size of a small shrimp, but a few Copepods also get caught in each mouthful. This food is extremely abundant, and because most Krill (and Copepods) eat phytoplankton directly the whale’s food-chain is very efficient. Krill also have the habit of living in dense swarms, making it easy to get a good mouthful, and that is important when each gulp of 100 tons of water needs to be filtered – there needs to be more energy in the food than is expended catching it!
Diving
Since Krill feed at the surface during the night, and only go down to about 100m during the daytime, Blue Whales do not need to dive very far (unlike Sperm Whales) and they only have to hold their breath for a few minutes. They also swim relatively slowly (at about walking pace) when feeding so as to expend as little energy as possible, but are capable of bursts of speed up to 30 miles per hour when pursued.
Blue Whale Enemies
Only the Killer Whale (Orca) and Man hunt the Blue Whale, and Killer Whales can only tackle small individuals. Before whalers took an interest in the Blue Whale in the mid nineteenth century (when boats became fast enough to chase them) there were over two hundred thousand, but the population was down to under two thousand in the 1960’s, and it is still an endangered species (with many man-made problems), and some authorities doubt its ability to recover fully.
The Latin Name
The genus Balaenoptera includes seven or eight species of rorqual (baleen whales with ‘pleated’ throats), but Linnaeus must have been having fun when he gave the Blue Whale the specific name ‘musculus’- it has two meanings, either ‘muscular’ (which is sensible) or ‘little mouse’ (which is a bit inappropriate for the largest mammal alive!).
Main reference: Collins Wild Guide – ‘Whales and Dolphins’ by Mark Carwardine, 2006.
Other articles by John Blatchford
