Killer Whales Go on Violent Killing Spree in California [Video]

Killer whales are truly living up to their name. Last week marked an unusual string of killer whale killings that shocked even experienced marine biologists.

According to a report from SFGate, there have been four kills in seven days by a pod of nine killer whales in Monterey Bay -- roughly one every other day. This strange killing spree baffles scientists, particularly Monteray Bay Whale Watch's Nancy Black, who described the frequency of the pod's attacks "unprecedented."

"This has never happened in my thirty years," Black said. "Just to witness that out in nature when you usually see that kind of thing on television is really spectacular."

The same group of nine killer whales -- also known as orcas -- are behind every attack, although a few individuals join the fray once in a while. During the first hunt, a total of 33 whales showed up for both the attack and the subsequent feast, according to a report from The Guardian.

Killer whales eat a wide variety of marine life including gray whale calves, humpback whale calves, seals, sea lions, dolphins, tuna and great white sharks. Because adult whales can overpower them, calves are usually too small to fight back. To get to the young, killer whales try to separate the mother from her calf while avoiding the adult's strong tail. This process can take anywhere from an hour to a few hours.

It seems the killer whales are becoming more efficient in their kills, though. The most recent killing involved the pod attacking a mother grey whale and her calf, a successful hunt that only took about 20 minutes. Black thinks the reason for the unusually fast kill was because the pair was skinnier than most grey whales.

Monterey Bay is a hunting ground for killer whales, especially during this season when grey whales migrate from Mexico to California. This year's migration was later than usual, so the hungry killer whales were waiting ravenously.

If there's one species protecting grey whales -- and other marine species -- from the vicious killings of orcas, it's humpback whales.

"In areas where killer whales are trying to catch prey, the humpbacks come charging in with trumpets blowing, all excited, and they try to prevent the killer whales from killing their prey, whether it's a seal or even a grey whale," Black explained to The Guardian.

It's not unusual for humpback whales to interfere when killer whales are on the attack. Last year, a paper even addressed the "altruistic" behavior.