Photo courtesy of DFO
Slender and elongated, the Blue whale is sleek and streamlined with a small, one foot high dorsal fin, long and pointed flippers, broad straight-edged flukes and a wide, flat head with one median ridge. About 55 to 68 ventral grooves or pleats extend from below the mouth to the navel. The blow holes are protected by large splash guards that appear to contract and expand as the animal breathes. One female Blue whale was measured at 110 feet long and weighed 190 tons. This is equivalent to the weight of 20 bull elephants and confirms that the Blue whale is the largest living animal on the earth today. On average Blue whales weigh from 80 to 150 tons and may attain a scientifically validated length of 98 feet. The heart of a Blue whale weighs a thousand pounds and it has an aorta large enough for a man to crawl through with ease. At eight months the calf is fifty feet long and weighs 50,000 pounds. Blue whales are dark bluish-grey and they possess two blow holes from which a fountain of water spouts fifty feet above the surface. Blue whales can reach speeds of 32 to 36 kilometers per hour but they most often cruise at 8 kilometers per hour. Generally they dive for up to fifteen minutes ater breathing six to twenty times at the surface over five minutes. Blue whales extend their dive duration by gliding and by taking advantage of negative buoyancy at increasing depths during deep dives. Blue whales can live to be up to eighty years old.
Blue whales mate and calve from late Fall to mid Winter in the Northern Hemisphere and peak mating season is in July in the Southern Hemisphere. Sexual maturity in both male and female Blue hales is reached at 5 to 15 years of age. After carrying the baby Blue whale in their womb for ten to eleven months the female Blue whale gives birth to a single 22 foot long calf. Calves drink about 200 pounds of milk per day until they are 45 feet long. Calves weigh six to eight tons at birth and are weaned at seven to nine months of age. Within thity minutes of birth the calf can swim. Blue whale milk is 50 percent fat. Twins are very rare and there is usually only one calf.
Blue whales consume up to four tons of food daily. Blue whales feed almost exclusively on euphasids (krill) although they may also take copepods, crabs and shrimp. About 50 to 70 throat pleats allow the throat of the Blue whale to expand thus forming a ventral gular pouch. Blue whales feed by swallowing vast quantities of water and krill into their mouths and then using the muscular action of the gular pouch and tongue to force the krill and copepods out through the baleen plates with the expelled water. Most of the krill and copepods are caught on the bristles of the 320 pairs of baleen plates where it can be scraped off with the tongue. Each of the baleen plates is 39 inches long and 21 inches wide and weighs about 200 pounds. Blue whales feed along productive cold water upwellings in temperate to polar waters from Spring to early Winter.
By far the largest threat to the Blue whale has been the commercial exploitation of whaler ships and up to 360 thousand Blue whales were harvested by whaler ships over six decades. By 1966 the Blue whale had received complete protection from whaler ship harvesting by the International Whaling Commission. Now there are only about 25,000 Blue whales left and only 1,255 Blue whales are left in the southern ocean of Antarctica. Between 600 and 1500 Blue whales survive in the North Atlantic and 250 Blue whales live in the Gulf of St. Lawrence. Ship strikes and fishing gear entanglements also take a significant toll upon the Blue whale population. Between 1980 and 1993 ship strikes killed six Blue whales off the coast of California and fishing gear entanglements killed 3 Blue whales in the Gulf of St. Lawrence since 1979.
Blue whales make an intense long duration call with more acoustic power than any other animal such that source levels are measured at 186 decibels. Vocalizations can last 13 seconds and range from 11 to 125 Hz.