Dolphins often work together to hunt by surrounding a school of fish. The fish are then trapped, and any that try to escape go right towards the dolphins. They may also blow bubbles (which oddly enough, terrifies the fish) and they won't dare to cross that "line." Instead, they try to jump over the bubbles above the water's surface. Because they are surrounded by dolphins, they jump right into their mouths.
Often times, dolphins may simply hunt alongside each other (for example, if they are looking for crustaceans or fish under the sand). In that case, they don't work as a team, but they are close together.
Many of them do yes. They work together in packs or pods to hunt.
A group of dolphins is called a pod. Pods can vary in size and may consist of anywhere from a few dolphins to several dozen individuals. Dolphins within a pod work together to hunt, communicate, and travel.
They hunt fish. Pods of dolphins will work together when they find a group of fish and they swim around the fish working them into a ball. Once they have done that they take turns going into the ball and eating the fish. There is an IMX DVD out about dolphins showing them doing this. It is pretty smart.
tuna
yes
Dolphins will usually eat fish for their diet. They will be able to do this because they hunt together in packs to catch their food. Dolphins don't eat plankton. They don't have the kind of mouths that'd allow them to filter plankton from the water.
hunt for food
Yes they will hunt in their groups called Pods
No. They hunt and eat live prey. Seals and dolphins are two that they will hunt.
people hunt them for their meat
The Aleuts
Unfortunately, they have been hunted by the Russians, with over 500 believed killed. However, the vast majority of humans perceive no need to hunt dolphins.