How Do Dolphins Get Their Resources in Order for Them to Live?

Oxygen

• Dolphin respiratory systems function in ways that are specifically adapted to life in the ocean. To breathe, they swim to the surface and exhale through a blowhole in the top of the head. They then inhale fresh air before diving again. A muscular flap covers the blowhole when a dolphin is under water, but it lifts out of the way with a simple contraction when the animal surfaces. Dolphins hold their breath under water for an average of 10 minutes between trips to the surface. During these long dives, their heart rate is very slow, so the oxygen in their lungs is absorbed slowly. As oxygen enters the dolphin's blood, most of it is shunted to the body's core to benefit the heart and other vital organs.

Food

• Dolphins are carnivores, meaning they are meat eaters. Their diet consists mainly of fish, squids and crustaceans, such as shrimp. They eat 4 to 6 percent of their body weight every day. With an average body weight of 400 to 600 lbs., that means an average dolphin eats somewhere between 16 and 36 lbs. of food a day. Dolphins' stomachs are compartmentalized, an arrangement that contributes to rapid digestion of all that fish. They do not chew their prey, but rather shake the fishes or rub and beat them on the seafloor until pieces break off. Dolphins also often eat a fish whole, swallowing it headfirst to keep the prey's fins from catching in the dolphin's throat.

Coastal Hunting

• In coastal areas, dolphins hunt for fish near reefs or in sea grass flats. A dolphin may hide quietly and wait for the prey to reveal itself with a noise that the dolphin can pinpoint through its excellent sense of hearing. Dolphins also hunt aggressively and use echolocation, a process of sending out sound waves and interpreting the echoes, to find larger prey or schools of fish. A group of five to 15 dolphins may surround a school of fish or work together to trap the fishes against a sand bar or other shoreline feature. Coastal dolphins also dig in the sandy sea bottom to find crustaceans.

Deepwater Hunting Behaviors

• Dolphins that live in the deeper offshore water often live in large groups of 100 or more. These dolphins work cooperatively while hunting, using the technique of echolocation to find schools of fish. The dolphins use their tails to stun fish, a technique called halking, or they may keep a school of fish together by kerplunking, whacking the water with their flukes to create a cloud of bubbles that confuse and frighten their prey.