THE ANIMAL FILES

Blue whale

Balaenoptera musculus

A giant with a very small menu.

A blue whale can make an entire boat look small, yet its usual meal is a cloud of tiny crustaceans. Follow that contrast and you meet an animal whose mouth is a filter, whose skin can carry an individual signature, and whose family tree leads back onto land.[1][2][3]

Follow the evidence ↓
Blue whale
Image: NOAA Photo Library · Commons · Public domain
Main food
Krill[1]
Feeding tool
Baleen, not rows of biting teeth[1]
Individual clue
Mottling around the dorsal fin[2]

How do you eat a swarm?

A feeding blue whale takes in water and prey together. Pleats beneath its throat expand; then the whale closes its mouth and forces water back out through hanging baleen plates. Krill remain inside. Think of separating pasta from water with a colander: the useful part of the comparison is the filtering, not a claim that the whale passively drifts through dinner. Dense prey patches matter.[1]

Read the pattern, not just the colour

“Blue” is a useful name, but blue-gray mottling is more informative than a flat colour label. Researchers photograph the animal’s side, including the dorsal-fin area, to compare identifying marks. A photograph can therefore be more than a souvenir: matched with place and date, it can help connect sightings of the same whale. One dramatic splash is less useful than a clear view of the relevant features.[2][1]

A sea animal with land relatives

Whales are mammals descended from land-living ancestors. Fossils and genetic evidence place cetaceans within the even-toed mammal lineage, with hippopotamuses as their closest living relatives outside cetaceans. That describes shared ancestry, not a modern hippo turning into a whale. Comparing fossils with living animals reveals changes that a line-up of present-day bodies alone would hide.[3]

A COMMON MIX-UP

Does a blue whale chase large fish because it is so large?

No. Its main prey is krill. A predator’s body size does not tell you the size of its usual prey; its feeding equipment is a better clue.[1]

TRY A LITTLE REASONING

You photographed blue whales on two different days. Which details could help test whether you saw the same individual?

Reveal the explanation

Compare clear views of the dorsal fin and nearby mottling, and keep each photograph’s date and location. These identifying features can connect sightings of an individual; a general color or size description cannot do the same job.[2][1]

Sources & editorial notes

Original explanations, checked against the sources below. The image has its own credit and licence above.

  1. NOAA Fisheries — Blue whale: appearance, behavior and diet
  2. IWC Southern Ocean Research Partnership — Whale photo-identification guide (PDF)
  3. American Museum of Natural History — Whale and dolphin evolution

Last fact check:

One discovery leads to another

Nile hippopotamusThe “river horse” has a surprising family tree.Hippopotamus amphibius ↗PlatypusEyes shut. Dinner detector on.Ornithorhynchus anatinus ↗Emperor penguinThe egg has no nest. Dad brings the warm floor.Aptenodytes forsteri ↗