Are humpback whales accidental "heroes" or do they actually have altruistic motivations?

These marine mammals, in their black-and-white uniforms, appear to rescue other animals such as seals and sunfish from killer whale or orca attacks.

Although the incidents seem to defy any explanation, scientists want to figure out the underlying reason behind the humpback whale's behavior. Their goal is to understand why and how these animals go out of their way to become "heroes."

Are These Spontaneous Rescue Missions?

Robert Pitman, a marine ecologist from the National Oceanic and Atmospheric Administration (NOAA), first observed a "rescue mission" by a humpback whale in 2009.

Back then, Pitman saw a pod of killer whales knock a seal off an Antarctic ice floe. The killer whales were about to finish off the seal when a humpback whale lifted the animal and placed it on its belly, keeping it out of harm's way.

A similar yet more dramatic incident occurred in Monterey Bay, California in May 2012, when a pod of killer whales targeted a gray whale and killed the whale's calf.

When the orcas first attacked the gray whales, two humpback whales were already on the scene. But after the calf was killed, 14 more humpbacks arrived — apparently to prevent the orcas from eating the dead calf.

In fact, one humpback whale seemed to station itself next to the dead calf, pointing its head toward the carcass and remaining a certain distance away.

The humpback whale loudly vocalized and slashed its tail whenever an orca came close, says whale researcher Alisa Schulman-Janiger.

According to Schulman-Janiger, the humpback whales slashed at the killer whales with their tails and flippers for six and a half hours.

Despite the thick swarms of krill nearby — the humpbacks' main choice for food — the marine mammals did not abandon the dead calf, she says.

Possible Explanations

Because this behavior continues to manifest in other parts of the world, Schulman-Janiger and Pitman opted to analyze 115 rescue incidents from published and unpublished sources.

The team's study found that only 11 percent of killer whale victims that humpback whales tried to save were humpback whale calves — meaning the animals aren't just protecting their own kind.

Other animals that humpback whales have rescued include harbor seals, gray whales, ocean sunfish and California sea lions.

Scientists wonder whether humpback whales possess altruistic behavior toward other species.

"Interspecific altruism, even if unintentional, could not be ruled out," the researchers wrote.

Indeed, these marine animals are the only cetacean creatures that deliberately tackle orca attacks and drive them off.

Schulman-Janiger says personal history could also affect the decision of a humpback whale to intervene.

Many humpbacks that stop killer whales bear scars from their earlier years, says Schulman-Janiger.

As adults, the humpbacks could become protective to help younger ones make it through their most vulnerable stage.

Furthermore, the adult humpbacks' response to non-whales could actually be accidental, in which the animals respond to the orcas' auditory signal, instead of tending to the species in trouble, she says.

Details of the new study are published in the journal Marine Mammal Science.

Photo: Mark Gunn | Flickr