Marine biologists are tracking a pod of killer whales in Monterey, California who have been on a mysterious hunting spree for the past seven days.

As proof, the latest attack by the orcas was captured on camera by Nancy Black, a local marine biologist, and owner of Monterey Bay Whale Watch.

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Describing the recent events as "unprecedented" in the animal world, Black admitted that she hasn't witnessed this type of strange behavior from orcas for the past 30 years.

She noted that the group of killer whales, which has been referred to by scientists as Emma's group, has exhibited such a high skill level for sea predators that they were able to separate a calf from her mother in just 20 minutes.

Black noted that such a maneuver would take about two to three hours.

"It's kind of exciting to see this group and how they've gotten really good at hunting," the biologist said, as she praised the skill level of the pod.

According to Black, there are several possible theories that could explain the killer whales' aggressive behavior, and why they went on a hunting spree.

These include the spring migration of gray whales to the area, to their traveling further south in the area.

"It's still a mystery," Black said, adding, "but they are very intelligent," as he described how orcas know when and where to hunt gray whales."

In the video, the mother gray whale is seen splashing and trying to protect her offspring, as they both appeared to be very skinny. 

Black noted that what has made their study more exciting is the entry of killer humpback whales into Monterey Bay early this year participating in the hunting spree.

She calculates that there could be in fact, be around 60 to 70 of the massive whale species in the area are involving themselves in the whale hunt.

"Humpbacks like to interfere with the killer whales for some strange reason," Black said.

"They seem to want to protect the prey," she added, explaining how the killer humpback whales will charge into the site, blow their trumpets and take part in the hunting spree.