Blue whale

Blue whales dwarf every creature to have lived on Earth. Adults stretch over 30 meters and weigh as much as 25 elephants. Despite their size, their diet consists almost entirely of tiny shrimp-like krill. Blue whales wear mottled gray-blue skin, often scarred by circular white patches from barnacles and cookiecutter sharks. Each has a tall, column-shaped blow that can shoot 9 meters into the air, making them easy to spot from distant ships.

During summer feeding seasons, blue whales travel to cold, productive waters near Antarctica, the North Pacific, or the North Atlantic. They lunge through dense krill swarms with open mouths, expanding throat pleats like an accordion to hold tons of water and prey. Muscular tongues then push the water back through comb-like baleen plates, trapping krill that are swallowed by the thousands. A single whale can eat four tons of krill per day to build the fat reserves needed for long migrations.

Breeding and calving occur in warmer tropical seas during winter. After a year-long pregnancy, females give birth to calves about seven meters long that already weigh two metric tons. Calves nurse on milk richer than heavy cream, gaining nearly 90 kilograms each day. Mothers and calves remain close, traveling thousands of kilometers to return to summer feeding grounds where the young learn to lunge feed alongside their parents.

Blue whales communicate with infrasonic songs that travel across ocean basins. Scientists use underwater microphones to trace these vocal highways and estimate population sizes. Commercial whaling in the 1900s killed hundreds of thousands of blue whales, but international protection since 1966 has allowed slow recovery. Today, the biggest threats include ship strikes, entanglement in fishing gear, and climate-driven shifts that move krill farther from traditional feeding areas. Shipping speed limits, rerouted lanes, and careful monitoring of krill stocks help safeguard these giants.