Photo: Tory Kallman / Monterey Bay Photo: Daniel Bianchetta / Monterey Bay Whale Watch Photo: Daniel Bianchetta / Monterey Bay Whale Watch Photo: Daniel Bianchetta / Monterey Bay Whale Watch Photo: Daniel Bianchetta / Monterey Bay Whale Watch Photo: Daniel Bianchetta / Monterey Bay Whale Watch

In case there was any doubt, this video proves killer whale season has officially started in the Monterey Bay.

A family of four killer whales targeted a gray whale and its calf just west of Carmel Bay Wednesday, all in close view of a whale watching boat. Nancy Black, marine biologist with Monterey Bay Whale Watch, said as soon as the orcas spotted the mother-and-child pair, they beelined straight for them.

"The killer whales immediately began working as a team to block the gray whales from traveling towards shore which is the only way they can escape these predators," said Black.

For the next 90 minutes, the orcas rammed the calf and pushed it underwater. All the while, the mother gray whale repeatedly tried to roll belly-up to push her baby above water, away from the persistent predators.

Black described the killer whales as "relentless," and they eventually succeeded in separating the gray whales. Once they killed the calf, they feasted for more than eight hours (and showed off a bit for the cameras — see for yourself in the video below).

Orcas often come to the Monterey Bay as a prime hunting ground in the spring, as gray whales are migrating from Baja California to Alaska for the summer. The mothers and their calves typically remain fairly close to the shore on the migration up the California coast because it's safer and food is more abundant.

However, as they come across the Monterey Bay, the geography makes it harder for them to stay close to the coast. Orcas hang around the bay waiting to take advantage of the young calves' vulnerability in deep, open water.

This particular pod of killer whales is known to researchers and tour guides in the area. They're often referred to as the "friendly pod" because of how curious they are towards boats, explained Black.

The pod is made up the matriarch Star, who has a reputation as a great hunter, plus her two adult sons and a young daughter. Star was first seen in and around the Monterey Bay back in 1992.

This hunt was the second in less than a week witnessed by tour groups. On Saturday, a pod of five killer whales (led by Star's daughter, funnily enough) was seen hunting and killing a gray whale.

"This predation event was tough to watch but the gray whale calf is an important source of food for many killer whales," said Black of Wednesday's hunt. "This is one of nature's greatest battles."

Read Alix Martichoux's latest stories and send her news tips at alix.martichoux@sfgate.com.