Blue whales are the largest animals on Earth. They have astounding body parts—tongues that weigh two tons, a heart as large as a small car and skin-folds that extend from beneath the tips of their lower jaws to their navels. When expanded, these folds increase the interior of a blue whale’s mouth to the size of a train’s box car. Blue whales can grow to 100 feet (30 m) in length and weigh as much as 150 tons—the weight of 30 elephants.
Instead of teeth, blue whales have 300 to 400 fringed baleen plates that hang from their upper jaws and strain their food. Blue whales strain and eat krill, a tiny, shrimplike invertebrate. A whale gulps a mouthful of water and krill, closes its mouth, pushes out the water with its tongue and then swallows its catch of krill. A blue whale’s esophagus is only four inches (10 cm) in diameter—so swallowing large fishes isn’t possible.
Blue whales visit Monterey Bay during the summer and fall. They come to eat, gulping tons of shrimplike krill. As their common name suggests, blue whales’ upper bodies are blue-gray. Their bellies are whitish to yellow. In Arctic or Antarctic waters, yellow diatoms (microscopic algae) often stick to blue whales’ underbodies, giving them a nickname of “sulfur bottom.”