What Is the Largest Marine Mammal?

The largest marine mammal is also the biggest animal ever to have lived on the planet. The blue whale (Balaenoptera musculus) is a massive aquatic mammal that has adapted to live in the thriving oceans. Being a mammal, the whale has to breathe oxygen. Other mammals have nostrils to take in air, but the blue whale has a breathing hole on its back. It can also exhale water through this hole, creating spouts 30 feet in height.

  1. Description

    • Blue whales are long, torpedo-shaped animals that grow between 82 to 105 feet in length and up to 200 tons in weight. They have flippers on either side of their bodies, which at one time were front legs. Their rear legs have joined together to make a large, flattened tail, used to propel the whale through the sea. The whale tends to be blue-gray in color, with a mottled lighter coloring running the length of its body. The animal's dorsal fin, located on its back, is only about a foot tall.

    Habitat and Range

    • Blue whales are the giants of the ocean and can go anywhere they want. They are found in tropical waters as well as in the cold waters in the planet's polar regions. Blue whales migrate between the northern and southern waters in the summer to the more equatorial waters in the winter months. The whales tend to stay out in the deep ocean, not venturing too close to the shoreline.

    Diet and Predators

    • Oddly, the largest animal on earth reaches this size by eating some of the planet's smallest animals. Blue whales eat up to four tons of small shrimp-like creatures called krill each day. They filter the krill through fringed plates in their mouths called baleen. They also inhale gallons of water, which they then spit out through these plates. The plates allow the water out but capture the tiny krill, which are then swallowed. Adult blue whales only have to fear human whalers as the pure size of the animal means no predator exists that can hunt them. Young whales may be at risk from killer whales and large sharks such as great whites.

    Life Cycle

    • Studying the way blue whales breed is so difficult that little is known about the process. It is known that pregnancies take around a year and birth takes place in warmer tropical waters. At birth, the babies are already around 25 feet in length and weigh 3 tons. A single offspring is born and will travel with its mother for between two and three years. Wild lifespans for blue whales are estimated to be around 80 to 90 years.