Blue Whale

Category: Sea Life

The largest living animal, the blue whale is a massive baleen whale, which means that in place of teeth its mouth is full of large plates used to filter tiny krill from the seawater.

Blue Whale

Blue Whale

Scientific & Common Names

Kingdom - Animalia

Phylum - Chordata

Class - Mammalia

Order - Artiodactyla

Infraorder - Cetacea

Family - Balaeonopteridae

Genus - Balaenoptera

Species - B. musculus

Common Names – Blue Whale


The blue whale is the largest living creature on earth, reaching lengths of over 100 feet. It can weigh over 400,000 lbs., making it not just the heaviest living animal, but also the heaviest animal ever known. True to its name, this whale is a dark blue grey above, fading to slightly lighter below. For its size, it is relatively sleek and slender compared to smaller, more heavy bodied whales.

There are at least two different types of blue whale, and may be up to four subspecies, but the most easily distinguished is the pygmy blue whale. This type is noticeably smaller than "true" blue whales, and features a shorter head and smaller dorsal fin.


Females will give birth to one calf every two to three years. Gestation lasts 11 months, and calves are usually born in warm waters during winter months. Calves weigh up to 7000 lbs. when born, and while growing and nursing they will gain up to 200 lbs. per day. They stay with their mothers until around nine months of age, at which point they go off on their own.


Blue whales feed only on krill, and eat up to six tons a day. They dive into schools of krill with their mouths wide open, filling and expanding their throat with krill and seawater, which is filtered through their baleen plates. Little is known about the day to day lives and social behaviors of blue whales, but they are known to travel by themselves or in small groups like other rorquals in the family Balaenopteridae. They sometimes travel with the smaller but closely related fin whale.


Due to their size and speed, blue whales are not easy to hunt. Early whalers targeted smaller, less powerful species until the advent of harpoon guns and steam-powered whaling vessels. Before this time, it was poorly understood and sightings were often believed to be sea monsters or other mythical creatures. Today, blue whales are popular for ecotourism, and are highly sought after for whale watchers.

Present status

Hunting seriously depleted blue whale populations before being outlawed, and they are still currently listed as "Endangered". Though they have very few natural predators, with only packs of killer whales giving any serious challenge, they are threatened by human activity and can be caught in fishing nets or struck by boats. Climate change is also likely to affect blue whales, since rising ocean temperatures can disrupt their migration patterns.



  2. Princeton Field Guides: Whales, Dolphins and Other Marine Mammals; Shirihai & Jarrett; 2016

  3. Guide to Marine Mammals of the World; Reeves, Stewart, Clapham & Powell; 2008