Sei whale



The sei whale (pronounced: say whale) is a medium to large sized whale living in almost all oceans in the world. They do, however, prefer warmer water and sometimes avoid the cold Arctic and Antarctic waters. Sei whales also tend to avoid coastal waters.800px-Cetacea_range_map_Sei_Whale In their genus of five species, these whales are the medium-sized animals.  Sei whales are baleen whales, which means they have long, hair-like structures, called baleen, that grow down from their upper jaw inside their mouth. These animals are gray or bluish-gray on their top side, and their bottom side is a whitish-gray. Sei whales look a lot like Bryde’s whales and fin whales. Because of this, many sei whale catches, especially in the 19th century, were mistaken for either of these two species or vice versa.


At one time, a Sei whale was marked in Antarctica and ten days later was killed by whalers. During these ten days, the whale had traveled 2,200 miles (4,000 km) from where it was tagged. This means that if it was traveling at a constant speed, it would have been going 9.16 miles (14.75 km) per hour the whole time. If it took any breaks, it would have had to have been going even faster some of the time.


Sei whales, like many other baleen whales, eat mainly zooplankton. They will sometimes also eat small fish and occasionally squid. An adult blue whale can eat up to 1,984 pounds (900 kg) of food each day! Although this may sound like a lot, it is justified by their size. Sei whales eat about as much relative to their body weight as humans do. In order to catch their food, sei whales take a HUGE gulp of ocean water. They will then use their baleen to strain out the ocean water and leave the fish and zooplankton in their mouth. The baleen on sei whales can be up to 32 inches (80 cm) long! Click here to see a video of a sei whale feeding.


Sei whales are huge animals. Even at birth they can weigh up to 1800 pounds (800 kg) and Sei_whale_sizebe 15 feet (4.5 m) long. This is three times as heavy as a large adult lion and slightly longer than a large adult elephant is tall! Once they are fully grown, sei whales can be up to 66 feet (20 m) long and weigh around 36 tons (33 metric tons). The females are larger than the males which only grow to around 58 feet (17.7 m) in length. This picture shows a grown sei whale relative to a human.

Whale stuff

Sei whales are not as good as some other whales at diving. They only stay under water for around 20 minutes at a time and rarely dive below 1,000 feet (300 m). While this is not very good by a whale’s standards, it is much better than humans can do. These whales have one ridge on the top of their head and 50 throat grooves, which is fewer than other whales. Sei whales make a blow or spout that is made of a thin cloud of water vapor and can reach up to 10 feet (3 m) high. Their dorsal fin is slightly hooked and is about two-thirds of the way back on the whale’s body. The backs of these and other whales are often marked with scars. These markings could be scars from a battle with a shark.

Life cycle

Between six and twelve years of age, sei whales start to mate. After an almost one year pregnancy, the female gives birth to normally one, but occasionally two babies. After nine months, the babies are weaned and can eat the same food as their mothers. Although it is hard to count all of the animals in the world, there are an estimated 12,000 to 80,000 Sei whales in the wild. These amazing animals can live for around 60 years in the wild.

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Photo credits:

  • Sei whale – Public domain
  • Sei whale range – Chris huh
  • Sei whale size comparison – Chris huh
  • Mystery animal -Bjørn Christian Tørrissen
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