What Do Blue Whales Eat? – A Useful Guide

what do blue whales eat

Food is definitely a highlight of my life and I’m pretty sure lots of people would agree with me on that.

It is such an important part of any animal’s life that every single species has evolved most physical traits to help with the process of successfully obtaining food.

If you are here it is because you, like myself, are an ocean lover and curious about learning everything there is to know about the animals that swim our seas, so today I will strive to answer the burning question that has crossed your mind: What do blue whales eat?

After all, they are the largest animal to ever exist, and when you weigh 200 tons and measure 33 m / 108.3 feet your appetite is surely nothing less than colossal. However, you might be surprised to know that the blue whale eats very very small things.

The blue whale is a carnivore and its diet consists almost entirely of krill which is an extremely small, shrimp-like crustacean. 

On today’s journey, I will take you on a tour of the prey items that make it into the blue whale’s menu, how much food is required by the largest animal in the world, how and where this cetacean finds enough food, and some more interesting facts regarding this creature’s diet.

What Do Blue Whales Actually Eat?

As I told you before, the main item on a blue whale’s menu is krill.

This small crustacean ranges in size from 0.8 to 6 cm / 0.3 – 2.4 in. and can be found in huge swarms near the ocean’s surface or at depths greater than 2,000 m / 6562 feet.

Krill is a highly nutritious source of protein that also provides the blue whale with a significant amount of vitamin A, and omega 3 fatty acids.

Even though krill can be found in oceans around the world they are particularly abundant in the cold waters off the coast of Antarctica.

For this reason, the blue whale spends most of its summer feeding in Antarctica before moving to warmer waters during the winter.

Unlike other whale species, this cetacean exhibits very flexible migratory patterns, or lack thereof, and its movements will usually be related to food availability.

What Do Blue Whales Eat Besides Krill?

The blue whale has highly specialized adaptations for feeding that result in it having an extremely limited diet.

As you already know krill makes up for most of the food intake of this whale but there are a few other items that make it on the menu, usually as a result of accidental bycatch. 

Other organisms that the blue whale will eat are:

  • Zooplankton: Extremely small (and sometimes microscopic) organisms that float in the water. This includes, but is not limited to, larvae of some fish, eggs of other animals, and protozoans which are single-celled eukaryotes. 
  • Fish: Various species of tiny fish.
  • Copepods: A group of tiny crustaceans.
  • Amphipods: A group of crustaceans that lack carapace. 

How Do Blue Whales Find Enough Food?

Now you may be wondering why the blue whale doesn’t just eat larger fish as it would certainly make its life easier.

Truth is that although this whale has an impressively large mouth (about 6 m – 20 feet long),  it can’t swallow anything larger than perhaps your closed fist as that is how big its throat is.

The blue whale belongs to a group of cetaceans that are known as baleen whales.

The word “baleen” refers to its specialized feeding system as these whales have no teeth, therefore must swallow prey whole, and instead have large hair-like bristles that hang down from the roof of their mouth.

These filaments on their upper jaws are made from a protein called keratin, the same one found on your nails and hair, and its job is to keep the blue whale’s tiny prey inside the mouth while the marine mammal gorges via its specialized filter-feeding system.

So how this works is that the blue whale has a huge mouth that it can open at an angle of almost 90 degrees thanks to an adaptation that allows this animal to dislocate its lower jaw. 

Additionally, this whale has between 60 – 88 ventral pleats on its mandible that work as an accordion allowing the blue whale’s mouth to stretch up to 4 times its original size while feeding. 

When a swarm of krill is spotted the blue whale will accelerate to swim at a speed of about 32 km / 20 miles per hour and open its mouth as wide as it can to take in vast quantities of food and water, 80.000 liters of nutrient-rich water to be exact. 

Once the whale closes its mouth it will use its tongue to push out the water while the baleen plates keep the prey inside the mouth so that it can be swallowed.

In places that are particularly rich in krill, a single gulp equals 360 kg / 794 lbs of food that is ingested. 

When it comes to feeding, the blue whale depends on successfully locating disconnected patches of prey in the ocean so it spends most of the day foraging in different areas and at different depths. What is certain is that summers in the Arctic are the best feeding grounds for these cetaceans.

How Much Food Does A Blue Whale Eat Per Day?

It had always been believed that an adult blue whale ate around 6 tons of food per day, however recent studies are showing that it is closer to 16 tons!

Something important to keep in mind though is that these giants don’t eat all year.

Actually, only around 100 days of the year are spent eating and during the remaining 265 days, the whale is traveling and breeding eating very little. 

More Foods That Blue Whales Eat

As you have already learned the blue whale is highly specialized for consuming a particular kind of prey.

It does occasionally eat a few other prey items as I mentioned above but they are normally a product of bycatch when chasing swarms of krill and do not represent a significant part of its diet.

This may include shrimp, small fish as well as small crustaceans. However, it’s mainly krill. The blue whale certainly loves its krill!

Final Thoughts

Today you have learned about the blue whale’s very special adaptations for eating 16 tons of food per day.

You have learned about other small animals, besides krill, that may end up on this behemoth’s diet, and most importantly, and you have learned that the largest animal alive is also the one who eats some of the smallest prey in the world!

I hope you had fun learning about the habits of this sea giant and I will see you next time!

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