The blue whale is the largest animal ever known to have lived on Earth, bigger than any dinosaur that ever walked the planet. Despite that massive size, it survives on some of the smallest creatures in the ocean.
From gigantic hearts to marathon migrations, here are the real facts behind this ocean giant.
Blue whales are the largest animals on the planet, reaching lengths of around 100 feet (with some individuals approaching 110 feet) and weighing up to 330,000 pounds, or roughly 150 tons.
A blue whale's heart weighs about 400 pounds — roughly the weight of a grand piano — and is the largest heart of any animal on Earth.
During deep dives a blue whale's heart rate can slow to as few as 2 beats per minute to conserve oxygen, then spike to 25-37 beats per minute when it surfaces to breathe.
Despite their enormous size, blue whales feed almost entirely on tiny shrimp-like krill, filtering them from the water with baleen plates instead of teeth.
A blue whale can eat several tons of krill a day during peak feeding season, with some estimates reaching up to 6 tons daily.
Blue whales produce some of the loudest and lowest-frequency sounds of any animal, and under the right ocean conditions their calls can travel hundreds of miles underwater.
Blue whales migrate thousands of miles between cold, krill-rich feeding grounds near the poles and warmer waters closer to the equator where they breed and give birth.
Blue whales aren't actually blue — their skin is a blue-gray color that can look brighter blue when seen through water.
Diatoms (a type of algae) sometimes coat a blue whale's underside, giving it a yellowish tint that earned the species the old nickname 'sulphur-bottom whale.'
Blue whales can live for 80 to 90 years, and they typically reach sexual maturity around age 10.
A thick layer of blubber helps blue whales stay warm in cold water, store energy, and stay buoyant during long migrations.
Blue whales were hunted to the brink of extinction in the 20th century for their oil, meat, and blubber, and they remain listed as endangered today despite decades of protection.
Blue whales usually cruise at around 5 miles per hour but can reach speeds of roughly 20 miles per hour or more in short bursts.
Blue whales typically dive for 10 to 20 minutes at a time, though they're capable of holding their breath for up to 30 minutes when needed.
Blue whales are generally solitary or travel in loose pairs, though small groups can gather in especially krill-rich feeding areas.
A female blue whale is pregnant for about 10 to 12 months and nurses her single calf for roughly 6 to 7 months before it becomes independent.
A newborn blue whale calf can already be around 23 feet long and gain as much as 200 pounds a day on its mother's fat-rich milk.
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