# Blue Whale — Facts, Threats & Conservation

*Balaenoptera musculus (Linnaeus, 1758)*

> The blue whale (Balaenoptera musculus) is the Endangered largest animal on Earth — a krill-filtering baleen whale found in all oceans, recovering slowly after twentieth-century whaling.

**IUCN status:** Endangered  ·  **WARN range:** All oceans — Arctic to Antarctic; migratory between feeding and breeding grounds

## Quick facts
| Fact | Value |
| --- | --- |
| IUCN status | Endangered |
| Length | Up to ~30 m |
| Diet | Krill and small crustaceans |
| Population | ~10,000–25,000 mature individuals |
| Feeding method | Lunge feeding with baleen |
| CITES | Appendix I |

## Scientific classification
- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Mammalia
- **Order:** Artiodactyla
- **Family:** Balaenopteridae
- **Species:** Balaenoptera musculus

## Conservation status
- **Status:** Endangered globally due to historic whaling depletion; populations increasing slowly under protection.
- **Population:** 10,000–25,000 mature individuals
- **Trend:** Increasing slowly
- **Assessed:** 2018
- **CITES:** Appendix I
- Antarctic subspecies remains heavily depleted relative to pre-whaling abundance.

## Key facts: Blue Whale
- Blue whales eat up to four tonnes of krill daily during feeding season.
- Commercial whaling reduced global numbers by roughly 99 percent before the 1966 moratorium.
- Ship strikes and ocean noise are now major threats alongside climate impacts on krill.
- Heart size can exceed 180 kg; arteries are wide enough for a child to crawl through.
- Subspecies include Antarctic, pygmy and northern Indian Ocean forms with distinct ranges.
- Recovery is measurable but slow — females produce one calf every two to three years.

## Anatomy and feeding
Blue whales belong to the rorqual family Balaenopteridae, characterised by pleated throat grooves that expand during feeding. The whale lunges through krill swarms, taking in tonnes of water, then expels it through baleen plates that trap prey.

Despite their size, blue whales feed almost exclusively on tiny euphausiid crustaceans. They accumulate fat reserves in summer feeding grounds — Antarctic, California, Sri Lanka — then migrate to warmer waters to calve, fasting or eating little during migration.

The blow can reach nine metres high. Flukes and mottled blue-grey skin with diatom film aid individual photo-identification in research catalogues.

## Migration and reproduction
Blue whales undertake some of the longest migrations of any mammal, travelling thousands of kilometres between poles and tropics. Timing follows krill blooms and calving advantages in warmer, predator-scarcer seas.

Gestation lasts about ten to twelve months. Calves are born roughly seven metres long, nursing on rich milk and gaining weight rapidly. Mothers invest heavily in single offspring; interbirth intervals of two to three years limit recovery speed.

Vocalisations — low-frequency pulses travelling hundreds of kilometres — may coordinate mating or maintain contact across ocean basins. Anthropogenic noise interferes with these calls.

## Whaling history and recovery
Industrial whaling in the twentieth century killed an estimated 350,000-plus blue whales, collapsing Antarctic populations especially. The International Whaling Commission protected blue whales in 1966; populations began slow increase thereafter.

The IUCN assessed the species as Endangered in 2018, estimating 10,000 to 25,000 mature individuals globally — a fraction of pre-whaling abundance. Antarctic blue whales remain at roughly 1 percent of historic numbers.

Legal protection continues, but illegal whaling is not the main modern risk. Ship strikes, entanglement, plastic ingestion and krill fishery expansion threaten recovery trajectories.

## Blue whales and people
Whale-watching for blue whales supports coastal economies in Sri Lanka, California and Quebec when conducted with approach limits. Scientific tagging reveals migration routes that inform shipping lane adjustments to reduce strikes.

Climate change may shift krill distribution, forcing whales to alter historic feeding grounds. International cooperation on ocean noise — from shipping, seismic surveys and naval sonar — is essential.

Readers can support blue whales indirectly through marine protected areas advocacy, sustainable seafood choices and organisations funding non-invasive research — not captivity, as blue whales cannot be kept humanely.

## Related WARN guides
Blue whales are baleen giants — read WARN's humpback whale guide for a recovering singer, the sperm whale page for toothed deep divers, and the whale hub for cetacean overview.

Dolphin and orca guides cover toothed relatives; manatee and dugong pages address other marine mammals.

Ship-strike reduction and krill protection are central to blue whale conservation.

## What WARN does
WARN's educational mission reaches readers across Brazil, Colombia, Indonesia, Malaysia and Pakistan — nations with coastlines where shipping, fisheries and pollution affect ocean giants. This blue whale guide is free outreach supporting informed care for marine habitats.

If this guide helps you understand wildlife and the pressures it faces, a gift to WARN supports habitat protection and free public education in our partner countries.

## Frequently asked questions: Blue Whale
### How big is a blue whale?
Up to about 30 metres long and 150–180 tonnes — the largest animal known. The tongue alone can weigh as much as an elephant.

### Are blue whales endangered?
Yes. The IUCN lists the blue whale as Endangered with roughly 10,000 to 25,000 mature individuals globally, recovering slowly from whaling.

### What do blue whales eat?
Almost exclusively krill — small shrimp-like crustaceans filtered through baleen. An adult may consume four tonnes of krill daily in feeding season.

### Where do blue whales live?
In all oceans. They feed in cold, productive waters such as the Antarctic and migrate to warmer latitudes to breed.

### Why did blue whales decline?
Commercial whaling killed hundreds of thousands before legal protection in 1966. Modern threats include ship strikes, ocean noise and climate effects on krill.

### How long do blue whales live?
Estimated 80 to 90 years, determined from ear-plug layers and photo-identification studies tracking individuals over decades.

## Sources
- [IUCN Red List — blue whale](https://www.iucnredlist.org/species/2477/50226194)
- [Smithsonian Ocean — blue whale](https://ocean.si.edu/ocean-life/marine-mammals/blue-whale)
- [Encyclopaedia Britannica — blue whale](https://www.britannica.com/animal/blue-whale)
- [Wikipedia — Blue whale](https://en.wikipedia.org/wiki/Blue_whale)

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Full guide: https://worldanimalrescuenetwork.org/wildlife-guides/blue-whale