Like all mammals, whales breathe air into lungs, are warm-blooded, feed their young milk and have some (although very little) hair. Their bodies resemble the streamlined form of a fish, while the forelimbs or flippers are paddle-shaped. The tail fins, or flukes, enable whales to propel themselves through the water. Most species of whale have a fin on their backs known as a dorsal fin. Beneath the skin lies a layer of fat called blubber. It serves as an energy reservoir and also as insulation. Whales breathe through blowholes, located on the top of the head so the animal can remain submerged. Baleen whales have two blowholes,while toothed whales have one.
Blue whales are federally listed as endangered. This species was once abundant, but advances in whaling technology made it easier for people to hunt them. With the rise of factory ships, blue whale populations plummeted. They are now protected internationally by a moratorium on whaling, and their numbers are rising. Ship noise, entanglement, and collisions may affect them in areas with high human activity, but occurrences of these events are rare. The effect that climate change will have on blue whales is uncertain.