The largest whale of them all: The Blue Whale

Happy New Year from all of us at Whale Scientists! My name is Bri, and this month I get to tell you all about the blue whale, the largest animal in the world.

One of my strongest memories as a kid was visiting my local aquarium and looking up in awe at the life-sized blue whale mother and calf replicas hanging from the ceiling. It was easy for me to look at the giant tanks down the hall and imagine what it might be like to swim with animals that large in an ocean so clean and vibrant. In this post, we cover interesting facts and the current conservation status of the blue whale (Balaenoptera musculus).

Blue whale swimming in the ocean.
Blue whale. Picture: NOAA Fisheries.

The largest animal on the planet

As adults, blue whales can reach a (confirmed) size of 29.9m (98  ft) and can weigh up to 199 tonnes! Blue whales have a slender fluke (tail) and a broad, U-shaped head. Though they are truly greyish-blue, these whales get their name from their underwater pale-blue hue.

Blue whales have a life span similar to humans, approximately 70 years. They reach sexual maturity at approximately ten years old, and females give birth every 2-3 years. Calves are about 8 meters (26 feet) long and weigh approximately 2.8–3 tons when born.

Blue whales eat almost exclusively krill; a single adult blue may consume as much as eight tons of krill per day! They achieve this with the help of throat grooves that widely expand the throat. This is a common quality across the rorqual family of whales.

Blue Whale Range.png
Global range of all blue whale subspecies.

A cosmopolitan species

There are four currently subspecies: B. m. musculus in the North Atlantic and North Pacific, B. m. intermedia in the Southern Ocean (Antarctic),  B. m. indica in the Northern Indian Ocean, and B. m. brevicauda (the pygmy blue whale) in the Indian Ocean and South Pacific Ocean. A fifth subspecies may exist around Chile, but it has yet to be officially determined.

Similar to their distant relatives the Humpback whale, Blue whales can undergo epic migrations across oceans to feed and breed. Each subspecies has a general range where they live; populations have different migratory patterns.

Just as there is a large repertoire of baleen whale songs, scientists are now beginning to believe that their migration routes may widely vary from the currently accepted patterns of seasonal migrations between high and low latitudes. Migration strategies may change further as climate change shifts ocean temperature and food distribution patterns.

Photo: Aquarium of the Pacific, my local aquarium that houses the mystical life-sized blue whale model.

Protecting the blue whale

It should be no surprise that because of their large size, blue whales were once one of the most commercially hunted baleen whales in the early 20th century. Like all whales, blue whales have been protected from commercial whaling since the 1960s. Worldwide populations are estimated to be between 10,000 and 25,000 animals, about 10% of what they once were. Rightfully so, the International Union for Conservation of Nature (IUCN) still classifies the blue whale as an endangered species.

Although commercial whaling is illegal, blue whales still face numerous threats. Most are from human activities like ship strikes, noise pollution, and various changes due to climate change. However, they also deal with natural threats, like calf predation by killer whales.

One of the easiest strategies to protect these migrating giants is to decrease ship speeds around critical areas. This allows captains to see the whales sooner and also lessens the disruptive noise from propellers. Hopefully, with continued action, we can continue to protect these beautiful blue giants.

Did you enjoy this post? Check out our other posts on large whales:

Whales are the engineers of their ecosystems

Brianna has a background in marine biology and currently works as a live-aboard deckhand/educator at the Los Angeles Maritime Institute (LAMI). Her research interests include ocean conservation, specifically in the high seas and polar regions, and identifying marine mammal vocalizations in the global soundscape. She is passionate about music and can’t write without coffee.

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