Graphic video shows orcas hunting and eating dolphins near San Diego. Orca scientist says they just like playing with their food.

• Orcas were spotted hunting dolphins off the coast of San Diego, in a graphic new drone video.
• This behavior is normal, especially since this pod of killer whales specializes in eating dolphins.
• Sometimes killer whales play with their food too. It's part of how they teach baby orcas to hunt.

Orcas belong to the dolphin family, but that doesn't stop them from hunting their cousins.

In a new video, a pod of these black-and-white creatures demonstrates how they earned the nickname "killer whale."

They weave silently through the water, opening their mouths and biting down through unsuspecting dolphins like pieces of bread. It's a brutal ballet.

After they've chased the group of dolphins and cornered one, the orcas swim around with their prey.

They even show off their catch to a boat full of whale watchers at the end of the video.

Domenic Biagini captured the video with a drone, off the coast of San Diego, on July 17. Watch the footage below.

It's a brutal video that shows the reality of the food chain in the ocean, said Lori Marino, the founder and president of The Whale Sanctuary Project and a neuroscientist who studies cetacean intelligence.

Killer whales eat a meat-based diet, but the prey they choose depends on what part of the world they live in. For example, there are certain pods of orcas off the coast of New Zealand that exclusively eat manta rays, Marino said. 

So there are groups of whales that specialize in eating dolphins and other smaller mammals, like the pod in the video.

The waters of Southern California are rich with dolphins and seals. So, for the orcas that cruise the area, eating dolphins is about a combination of opportunity and interest, Marino explained.

This dolphin-hunting pod visits the San Diego coast once or twice a year, according to Biagini, who runs a local whale-watching operation, called Gone Whale Watching. He stressed that these orcas really, really, really prefer dolphins.

"We often see them completely ignore seals or sea lions, and have even seen sea lions traveling with this group of orcas," Biagini told Insider in an email.

"I think the most surprising thing I've seen orcas do is go out of their way to come over to our boat and show us their fresh kill," he added.

The orcas are playing and teaching their young

You also see that the orcas in the video are hunting the dolphins in a pack, which is emblematic of another part of whale behavior — observational learning, Marino said.

The larger whales are likely adults teaching the smaller, juvenile whales how to hunt. "It's not uncommon for them to show, to teach, if you will, their children, their offspring, how to get the food that they need," she told Insider.

That's why you see some of them taking their time approaching their prey from below and playing with their catch before eating it. Marino said this is likely them trying to clearly demonstrate how to capture their targets. 

Watching the whales tear into the dolphins so flippantly seems almost cruel. But Marino explained that they're just doing what other apex predators, like cats, or even humans, do with their food.

"People don't like to think about it, but they probably find it fun to play with their food before they eat it," she said.