The largest creature ever known to have existed on Earth is the present-day blue whale. The largest dinosaur attained a length of about 22 m and weighed about 36 tons. Today’s blue whale is even larger than its ancestors, and may reach a total length of 33 m and a weight of 145 tons. This giant animal is placid and shy. On the ocean surface, its normal cruising speed is about 12 knots, but it is capable of attaining 20 knots in short bursts. The maximum reported depth reached by the species is 194 fathoms. It is capable of remaining submerged beneath the surface for 50 minutes, although 10 to 15 minutes is more typical. The life span of a blue whale is about 30 years. The calves measure 7 m at birth and weigh about 2 tons. By the time they are a year old, the youngsters measure 18 m.
Blue whales comprised about 90 percent of the whaling industry’s total catch during the early part of this century. In 1931, more than 30,000 of these majestic creatures were killed. Since then, the blue whale population has declined and was on the brink of extinction. Today about 11,000 are suspected to exist. The blue whale is the largest animal on Earth, some as long as 100 feet and weighing up to 300,000 pounds. But size does not protect this swift, powerful mammal from the threat of extinction that has loomed over them since the 19th century, when their population was cut down to 1 percent of its original size. There is not one specific factor in their endangered status, but rather, there are several reasons why this gentle giant is on the verge of extinction.
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o In the 1900s, whales meant huge profits to deep sea fishermen. From one whale, 120 barrels of oil could be produced. Fishermen improved the numbers of catches by perfecting whale catching techniques and they used harpoons for spearing the giant beast. Their population was cut down to 1 percent of its original size. The thick layer of blubber on a blue whale is to keep it warm, but humans have found multiple other uses for the tissue. It is used for the production of fuel, oil, soap and candles. Their baleen was used to make brushes and corsets rather than filter krill for the animal’s food. Hunting has been the biggest downfall of the population of this species due to the financial gains humans can make from their bodies. It is no longer considered a problem due to the ongoing efforts of worldwide conservation efforts.
o Rather than sight, blue whales use echolocation to determine their location and direction. This ultrasonic noise helps guide them along and avoid objects and swimming in shallow waters. When the navy tests equipment underwater, the sound and vibration can create interference that confuses the whale, sometimes causing them to beach themselves or get hit by ships. Being struck by ships is now the biggest threat to the blue whale population. In 2007, three blue whale fatalities were confirmed to be caused by collisions with ships. The problem has gotten so serious that the National Oceanic and Atmospheric Association (NOAA) is attempting to lower boat speed limits and consolidate shipping routes to reduce a ship’s chance of encountering a whale.
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Environmental Pollution and Degradation
Chemicals such as pesticides and oil are a serious problem for blue whales. These toxins collect in the fat stores of adult whales and contaminate a nursing cow’s milk. Environmental pollution leading to an increase of ocean water temperature has several negative effects on the well-being of blue whales. The warmer water harbors the growth of viruses, parasites, and toxic algae, and it also accelerates the melting of the glacial ice that provides krill with their diet, phytoplankton. Because krill make up a large portion of the blue whale diet, the melting ice has an effect on this life cycle.
Fishing nets and other gear pose a problem to the blue whale due to the risk of entanglement and injury. Whales caught in nets can break free with the net still attached and later become strangled or unable to swim properly, mate or eat. The harvesting of krill reduces the blue whale’s food supply. Krill is used as a food for humans and their pets and livestock, as well as an ingredient in dietary supplements. When they are overfished in an area, the whales nearby are left with a depleted food source.
Because it takes so long for blue whales to naturally replenish their own numbers, they have problems keeping their population established when so many of them are killed by unnatural and human causes. It takes a year for a pregnant blue whale to give birth and a decade or more for a new blue whale to reach sexual maturity. Once a whale is able to, it is still hard-pressed to find a mate, since the populations are so sparse and widespread. Blue whales in the northern hemisphere never come into contact with those in the southern hemisphere, meaning they have to mate separately in a small, limited gene pool.