The Blue Whale is the largest animal on Earth! They grow to be 80 feet long and weigh 120 to 150 tons (or over 300,000 pounds). Females are larger than males. Did you know that the heart of a blue whale weighs about 1,000 pounds? That's as much as a small car! A blue whale has blue-gray skin with whiteish spots. The belly often has yellow specks. This huge mammal has thin flippers about 8 feet long. However, its triangular dorsal fin is only 1 foot in length, about 3/4 of the way down the body. The body itself is slender in shape with a broad, flat head. The blowhole is at the tip of the snout, just past a ridge on the top of the head.
Blue whales are found throughout the oceans of the world. Even though they are so large, they eat small shrip-like animals called krill. During the summer months when krill are plentiful, a blue whale may eat as much as 4 tons of krill a day! Blue whales have a series of fringes on each side of the upper jaw instead of teeth. These fringes are called keretin, and they act as a filter to trap food on the inside to be swallowed while leaving behind the water.
Blue whales are sometimes seen singly, but they like to live in small groups or in pairs. Sometimes looser, larger groups of up to 50 whales have been seen. These mammals mate beginning at about age 8. Females will give birth to live calves every 3 years or so. They carry their young for 12 months and then migrate to warm tropical waters to give birth. After birth, mothers will nurse the calves for 8 months. During this time, each calf will drink up to 100 gallons of milk a day! Whales have long been in danger from human hunters. Although laws exist to protect them, whaling is still a profitable industry and whale numbers are shrinking.